Abstracts from Society for Neuroscience (SFN) New Orleans, Louisiana | November 8-12, 2003

47 entries found for : sfn2003

Reduced scratching in rats receiving intracisternal substance-saporin to ablate cervical superficial dorsal horn neurons that express NK-1 receptors

Carstens EE, Iodi-Carstens M, Simons CT (2003) Reduced scratching in rats receiving intracisternal substance-saporin to ablate cervical superficial dorsal horn neurons that express NK-1 receptors. Neuroscience 2003 Abstracts 908.2. Society for Neuroscience, New Orleans, LA.

Summary: While glutamate and the neuropeptide substance P (SP) are involved in the spinal neurotransmission of nociceptive signals, little is known about transmitters involved in itch. We investigated a role for SP in itch by determining if scratching behavior is affected by selective neurotoxic destruction of cervical superficial dorsal neurons that express NK-1 receptors for SP. Sprague-Dawley rats received intracisternal microinjection of SP conjugated to saporin (SP-SAP; 2.27 μM/ 20 μl). Controls received saporin (SAP) only. At least 2 wk post-surgery, rats were tested for dose-related hindlimb scratching directed toward the site of intradermal microinjection of serotonin (5-HT; 50, 100 or 200 μg/10 μl) or saline (control) into the nape of the neck, with at least 1 wk between sessions for each dose. After the intradermal injection, rats were videotaped for 44 min. The numbers and durations of individual scratching bouts were counted and averaged for each dose. Rats receiving SAP exhibited a dose-related increase in scratching bouts similar to naïve rats. Rats receiving SP-SAP exhibited significantly reduced scratching (to ~38%) at all 5-HT doses. Individual bout durations (~2 s) did not vary significantly between groups or by dose of 5-HT. After behavioral testing, rats were perfused with fixative and caudal medullary and cervical spinal cord sections processed immunohistochemically for NK-1 receptors. Tissue from SAP-treated rats exhibited a normal distribution of pronounced NK-1 immunoreactivity in superficial layers of the dorsal horn at caudal medullary through C5 levels, while in SP-SAP-treated rats there was a complete absence of NK-1 immunoreactivity at these levels. These results indicate that SP plays an important role in neurotransmission from itch-signaling primary afferent fibers to second-order neurons in the superficial dorsal horn.

Related Products: SP-SAP (Cat. #IT-07)

Lateralization of the attentional functions mediated via cortical cholinergic inputs

Sarter MF, Martinez V, Bruno JP (2003) Lateralization of the attentional functions mediated via cortical cholinergic inputs. Neuroscience 2003 Abstracts 921.20. Society for Neuroscience, New Orleans, LA.

Summary: The role of basal forebrain (BF) corticopetal cholinergic projections in mediating attentional processing has been well established. For example, bilateral cortical cholinergic deafferentation produces robust impairments in attention. Neuropsychological and neuroimaging studies have postulated that attentional functions and capacities are mediated primarily via a lateralized, right-hemispheric network. The present study tested the general hypothesis that the attentional functions of cortical cholinergic inputs likewise are lateralized and thus that right-hemisphere cortical cholinergic deafferentation yields more severe attentional impairments. Rats were trained to perform an operant sustained attention task. Upon reaching criterion performance, unilateral cortical cholinergic deafferentation was produced by infusions of 192-IgG saporin into either the left or right BF. Compared with the performance of sham-operated animals and animals with left-hemispheric lesions, right-hemispheric cortical cholinergic deafferentation resulted in a persistent and selective decrease in the detection of signals (hits), mirroring the more potent but similarly selective effects of bilateral lesions. In contrast, left cortical cholinergic deafferentation did not affect hits but decreased the number of rejections in non-signal trials. These data extend previous studies suggesting that the integrity of the right cortical cholinergic input system is necessary for signal detection (Bushnell et al. 1998). Furthermore, the present data substantiate the assumption that the detection of signals and the rejection of non-signals are based on fundamentally different cognitive operations, and that the cholinergic mediation of these two operations is lateralized.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Noradrenergic, but not cholinergic, deafferentation of the infralimbic/prelimbic cortex impairs attentional set-shifting

Eichenbaum HB, Ross R, Raji A, McGaughy JA (2003) Noradrenergic, but not cholinergic, deafferentation of the infralimbic/prelimbic cortex impairs attentional set-shifting. Neuroscience 2003 Abstracts 940.7. Society for Neuroscience, New Orleans, LA.

Summary: Damage to the prefrontal cortex in humans produces deficits in the ability to shift attention to a previously irrelevant stimulus dimension (extra-dimensional shift; EDS) while sparing reversal and intra-dimensional shifts (a novel discrimination without a change in the relevant dimension; IDS). Data from human subjects has also shown the administration of noradrenergic agonists and antagonists disrupts EDS suggesting a role for coeruleal-cortical norepinephrine (NE). Usher and colleagues have proposed that high, tonic levels of NE may maximize behavioral flexibility to allow an optimal responsiveness to changes in the environment e.g. the predictability of reinforcement (Usher et al., Science 283, 1999). Based on these data, a loss of NE would be predicted to impair attentional set-shifting. In a rodent model of attentional set-shifting developed by Brown and colleagues, excitotoxic lesions of the infralimbic/prelimbic cortex (IL/PL) produced impairments in EDS but not IDS or reversal learning (J. Neurosci. 20, 2000). This study confirmed the importance of IL/PL to EDS, but did not address the role of NE in this type of cognition. In the current study, rats were infused with anti-dopamine beta-hydroxylase-saporin (NE-SAP)in IL/PL (0.01 µ g/ µl; 0.5 µl/hemisphere) to produce noradrenergic deafferentation, 192 IgG saporin (ACH-SAP; 0.01 µ g/ µl; 0.5 µl/hemisphere)to produce cholinergic deafferentation, or vehicle then tested in an attentional set-shifting task. NE-SAP rats were impaired in EDS but not in IDS or reversal learning. In contrast, ACH-SAP rats showed no impairment in any aspect of the task. The effect of DBH-SAP lesions on EDS support the hypothesis that NE, but not ACH, is critical to the adaptation of behavior to changes in reinforcement contingencies. The lack of effect of these lesions on reversal learning suggest the robustness of this effect may vary with the extent of behavioral adaptation required.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Effect of selective cholinergic lesion of the septohippocampal pathway on the carbachol stimulated GTPγS binding in rat hippocampus

Pokala VN, Witt-Enderby PA, Johnson DA (2003) Effect of selective cholinergic lesion of the septohippocampal pathway on the carbachol stimulated GTPγS binding in rat hippocampus. Neuroscience 2003 Abstracts 799.7. Society for Neuroscience, New Orleans, LA.

Summary: Previously we have shown that selective lesion of the septohippocampal cholinergic pathway in the rat resulted in a significant decrease in hippocampal extracellular acetylcholine concentration and an increase in muscarinic receptor binding. The intent of this study was to investigate the effect of selective cholinergic lesion of the septohippocampal pathway on muscarinic receptor-coupled G protein activation. Measurement of agonist-stimulated GTP〔γ-35S〕 binding was used as a function of ligand-receptor interactions. Sprague-Dawley rats were infused into the medial septum with either the selective cholinergic immunotoxin 192 IgG-saporin (SAP) (0.22 μg in 1μl aCSF) or vehicle. After 6 weeks the rats were euthanized and the hippocampus dissected from the brain and quickly frozen. Hippocampal homogenate was analyzed for GTPγS binding following exposure to the muscarinic agonist carbachol (1 nM-10 mM). Data were analyzed to obtain EC50 of carbachol and Emax values for GTPγS binding using non-linear regression analysis. The results demonstrated, in control animals carbachol stimulated 35S GTPγS binding to be 150% over basal with an EC50 value of approximately 100 μM. However, in SAP lesioned animals no concentration dependent increase in 35S GTPγS binding occurred. Therefore, though we saw an increase in the muscarinic receptor binding at the hippocampus on SAP lesioning, these receptors seem to be nonfunctional.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Substance P-saporin lesions of NK1-receptor expressing neurons in the medullary raphe reduce central chemoreception in sleep and wakefulness

Nattie EE, Li A (2003) Substance P-saporin lesions of NK1-receptor expressing neurons in the medullary raphe reduce central chemoreception in sleep and wakefulness. Neuroscience 2003 Abstracts 826.7. Society for Neuroscience, New Orleans, LA.

Summary: Breathing, especially in sleep, depends on a CO2-related drive that comes from central chemoreceptors. Many brainstem chemoreceptor sites contain NK1-receptor expressing neurons and cell specific killing of them at one site, the retrotrapezoid nucleus, by injection of substance P-saporin (SP-SAP)produces hypoventilation and reduced chemosensitivity (J. Physiol. 544.2: 603-616, 2002). Here we focus on the medullary raphe, a putative chemoreceptor site rich in NK1-receptor expressing neurons. We studied rats, instrumented with EEG and EMG electrodes for sleep determination, before and during the two weeks after placing two injections (0.1 pmole in 100 nl of SP-SAP) 1 mm apart in the medullary raphe. SP-SAP injections reduced the number of NK1 receptor expressing neurons by 53% compared to controls injected with IgG-SAP (P< 0.01, two-way ANOVA). Room air breathing was unaffected in sleep or wakefulness. The level of breathing during inhalation of 7% CO2 at 7 and 14 days was reduced by 13 and 22%, respectively, in NREM sleep (P < 0.01, two way ANOVA) and by 19 and 24%, respectively, in wakefulness (P < 0.01, two way ANOVA). Body temperature, resting metabolic rate, and sleep cycling were not significantly affected. These SP-SAP injections did not significantly reduce the number of medullary raphe serotonergic neurons as determined by TPOH immunoreactivity. We conclude that, as in the retrotrapezoid nucleus, NK1 receptor expressing neurons in the medullary raphe are involved in central chemoreception.

Related Products: SP-SAP (Cat. #IT-07)

Poster: Immunotoxic destruction of distinct catecholaminergic neuron populations disrupts the reproductive response to glucoprivation in female rats

Dinh TT, I’Anson H, Ritter S (2003) Poster: Immunotoxic destruction of distinct catecholaminergic neuron populations disrupts the reproductive response to glucoprivation in female rats. Neuroscience 2003 Abstracts 827.13. Society for Neuroscience, New Orleans, LA.

Summary: Chronic glucoprivation suppresses estrous cyclicity in hamsters (Schneider et al. 1997) and rats (I'Anson et al. 2003). This suppression can be viewed as an adaptive glucoregulatory response since by delaying pregnancy, it conserves metabolic fuels for maternal survival. Our previous work shows that corticosterone, feeding and adrenal medullary responses to glucoprivation are controlled by hindbrain glucose sensing cells and require activation of ascending or descending catecholamine neurons. The glucoreceptors responsible for the delay of estrous also appear to be located in hindbrain, since fourth ventricular infusion of low 2-deoxy-D-glucose (2DG) doses suppresses pulsatile LH secretion in rats (Nagatani et al. 1996). Here we tested the involvement of catecholamine neurons in suppressing estrous cycles during chronic glucoprivation. We microinjected the retrogradely transported immunotoxin, anti-dopamine beta hydroxylase (dbh)-conjugated to saporin (DSAP), bilaterally into the paraventricular nucleus of the hypothalamus (PVH) of female rats to selectively destroy dbh-containing catecholamine neurons projecting to this area. Neither DSAP nor unconjugated saporin (SAP) control injections altered basal estrous cycle length. To assess effects of chronic 2DG, rats were injected with 2DG (200 mg/kg every 6 hr for 72 hr) beginning 24 hr after detection of estrous following two normal 4-5 day cycles. Chronic glucoprivation increased cycle length significantly in 7/8 SAP controls but in only 1/8 DSAP rats. Lesion effectiveness and selectivity were confirmed by immunohistochemistry. Thus, hindbrain catecholamine neurons with projections to the PVH are not required for estrous cyclicity when metabolic fuels are abundant, but are required for inhibition of reproductive function during chronic glucose deficit.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Hypothalamic injection of targeted toxin for cholecystokinin receptive neurons leads to increased 24 hour food intake and weight gain

Zhang J, Speth RC, Simasko S, Ritter RC (2003) Hypothalamic injection of targeted toxin for cholecystokinin receptive neurons leads to increased 24 hour food intake and weight gain. Neuroscience 2003 Abstracts 830.3. Society for Neuroscience, New Orleans, LA.

Summary: Peptides conjugated to the ribosomal toxin, saporin, bind to their specific G-protein coupled receptors, and are internalized. Once internalized, saporin inactivates ribosomes, selectively killing the receptive cells. We are using cholecystokinin (CCK)-saporin to selectively destroy CCK receptive neurons that may participate in the control of food intake and body weight. We have demonstrated that CCK-saporin binds to CCK-A receptors (Approximate IC50, 3nM), and evokes an increase in cytosolic calcium, which is blocked by the CCK-A receptor antagonist, lorglumide. Thus CCK-saporin has properties that recommend it as a targeted toxin of CCK-receptive neurons. We injected CCK-saporin (138 nM in 500 nl) bilaterally into the medial hypothalamus, an area where CCK-A receptors are expressed. CCK-saporin did not change 24h chow intake or weight gain. However, when rats were fed high fat diet, CCK-saporin treated rats increased their 24h food intake and gained nearly twice the weight as control rats during 14 days on this diet. Following an overnight fast CCK-saporin injected rats ate significantly more high fat diet than controls during the first 30 min after return of food. Nonetheless, both the CCK-saporin injected rats and controls reduced their food intake in response to intraperitoneal CCK-8. Our results suggest that ventromedial hypothalamic CCK receptors participate in control of 24h food intake and body weight gain. Our results also suggest that CCK-saporin may be a valuable tool for investigating the participation of discrete populations of CCK-sensitive neurons in various physiological responses.

Related Products: CCK-SAP (Cat. #IT-31)

Altered CCK binding in the dorsal vagal complex following cytotoxic lesion of the nodose ganglion

Treece BR, Speth RC, Ritter RC, Burns GA (2003) Altered CCK binding in the dorsal vagal complex following cytotoxic lesion of the nodose ganglion. Neuroscience 2003 Abstracts 830.5. Society for Neuroscience, New Orleans, LA.

Summary: CCK reduces meal size by activating a specific subpopulation (30%-38%) of vagal afferent neurons. MK-801, attenuates reduction of food intake by CCK and increases meal size. We hypothesized that vagal afferents that are sensitive to excitatory amino acids might express CCK receptors and thereby mediate effects of both CCK and MK-801. Therefore we examined I125CCK-8 binding in the dorsal vagal complex, following unilateral nodosectomy or cytotoxic lesion of nodose cell bodies. To destroy vagal afferent cell bodies and their central projections we made unilateral intranodose injections of NMDA/kainic acid, which has been shown to destroy about 40% of vagal afferents. We also made intranodose injections of CCK-saporin (CCK-SAP), a novel cytotoxin, which appears to destroy vagal afferents when the ribosomal toxin, saporin, is selectively internalized along with the CCK/receptor complex. In some rats we completely eliminated vagal afferents on one side via nodosectomy. We found that this produced significant ipsilateral reduction in CCK binding in the nucleus of the solitary tract (NTS). Intranodose injection of NMDA/kainate or CCK-SAP also resulted in significantly reduced CCK binding in the NTS, ipsilateral to the injected nodose. The reduction of NTS CCK binding following nodosectomy, NMDA/kainate or CCK-SAP injection did not differ significantly. Interestingly, CCK binding appeared to be reduced in the vagal dorsal motor nucleus, ipsilateral to nodose removal, but was increased ipsilateral to CCK-SAP injection. We conclude that CCK-SAP destroys a subpopulation of vagal afferents that express CCK receptors and that intranodose NMDA/kainate destroys a partially overlapping afferent subpopulation that also expresses CCK receptors. Finally, our data suggest that expression of CCK binding in the dorsal motor nucleus may be controlled by feedback from CCK sensitive vagal afferents.

Related Products: CCK-SAP (Cat. #IT-31)

Combined lesions of central cholinergic and noradrenergic denervation in the rat using 192 IgG-saporin and DSP-4 as an animal model of Alzheimer’s disease

Kolasa K, Harrell LE (2003) Combined lesions of central cholinergic and noradrenergic denervation in the rat using 192 IgG-saporin and DSP-4 as an animal model of Alzheimer's disease. Neuroscience 2003 Abstracts 842.6. Society for Neuroscience, New Orleans, LA.

Summary: To better model the consequences of persistent cholinergic hypofunction observed in Alzheimer’s disease, medial septum (MS) lesions were made by using specific cholinotoxin 192-IgG saporin. In this study the effect of simultaneous hippocampal cholinergic denervation, induced by intraseptal injection of 192-IgG saporin, and central noradrenergic denervation, induced by systemic injection of DSP-4 (N-[2-chloroethyl]-N-ethyl-2-bromobenzylamine) was examined in the rat dorsal hippocampus. DSP-4, an adrenergic neurotoxin selective for locus coeruleus innervated brain regions, induced a decrease in norepinephrine (NE) concentration in hippocampus. MS lesions resulted not only in selective cholinergic denervation of hippocampus (CD; superior cervical ganglion removed to prevent ingrowth of peripheral NE fibers), but also ingrowth of NE fibers into the hippocampus (HI; superior cervical ganglion left intact). MS lesions also resulted in a significant loss of choline-acetyltransferase activity in HI and CD groups, and an increase in NE in the HI group. In the HI group, but not in CD or control groups, visualization of hippocampus revealed a dense NE innervation with fine NE fibers with varicosities. Combination of MS lesion and DSP-4 treatment resulted in a reduction of NE concentration in HI group, with concomitant decrease in visualization of NE fibers. Those that remained were thick with sparse varicosities, possibly derived from peripheral sympathetic ingrowth. Elevated NE concentration and NE fiber number following specific cholinergic lesions might reflect compensatory sprouting of both central and peripheral adrenergic fibers into the hippocampus. Thus, noradrenergic sprouting in response to cholinergic denervation of hippocampus might be a valuable model for studying mechanisms as well as the consequences of neuronal plasticity in the mature CNS.

Related Products: 192-IgG-SAP (Cat. #IT-01)

The effects of ethanol and cholinergic lesions on anxiety in mice

Hummer TA, Johnson AD, Givens B (2003) The effects of ethanol and cholinergic lesions on anxiety in mice. Neuroscience 2003 Abstracts 859.16. Society for Neuroscience, New Orleans, LA.

Summary: Ethanol’s anxiolytic properties in mice are well-documented as measured with an elevated plus-maze. The effect of IP ethanol injections and cholinergic lesions on anxiety was investigated. Animals were injected with 0.5 µg of the cholinergic immunotoxin anti-murine-p75-saporin or control saline into the right lateral ventricle. After recovery (14-17 d), mice were given an IP 1.6 g/kg ethanol (10% v/v) or vehicle injection. After 60 min, animals were placed on the elevated plus-maze for a 10 min session and then perfused. Mice displayed increased open arm entries and time following ethanol. Saporin did not effect measures of anxiety nor interact with the effects of ethanol. Choline acetyltransferase staining was performed to confirm the extent of the cholinergic lesioning, and ethanol assays confirmed the presence or absence of ethanol in the blood stream. The research demonstrates that, as measured in the plus-maze, the basal forebrain cholinergic system has no significant involvement in anxiety nor in ethanol’s anxiolytic effects.

Related Products: mu p75-SAP (Cat. #IT-16)

Testosterone treatment protects motoneurons from dendritic atrophy following contralateral motoneuron depletion

Fargo KN, Sengelaub DR (2003) Testosterone treatment protects motoneurons from dendritic atrophy following contralateral motoneuron depletion. Neuroscience 2003 Abstracts 602.2. Society for Neuroscience, New Orleans, LA.

Summary: In male rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) project to the bulbocavernosus and levator ani muscles. SNB motoneurons and their target muscles are dependent on testosterone (T). We have previously demonstrated that unilateral depletion of SNB motoneurons induces dendritic atrophy in contralateral SNB motoneurons, and this atrophy is prevented by androgen manipulation. In the previous study, males were castrated for 6 weeks, then given replacement T coincident with motoneuron depletion. Because castration results in SNB dendritic retraction, and T replacement causes SNB dendrites to regrow to normal length, it is possible that the regressive changes or the active regrowth are involved in the protective effect of T manipulation. Alternatively, it may be that the effect can be accounted for simply by the high-normal levels of T produced by hormone implants. In the present experiment we show that SNB motoneuron dendrites are protected from contralateral motoneuron depletion by exogenous T alone (i.e., with no delay between castration and T replacement). We unilaterally depleted SNB motoneurons in male rats by intramuscular injection of cholera toxin conjugated saporin. Simultaneously, some saporin-injected rats were castrated and immediately given implants containing T. Four weeks later, contralateral SNB motoneurons were labeled with cholera toxin conjugated HRP, and dendritic arbors were reconstructed in 3 dimensions. A group of intact control males was also used. Contralateral SNB motoneuron depletion induced dendritic retraction to about 40% of normal length, but this atrophy was completely prevented by T treatment. Thus, the protective effect of T on SNB motoneurons is not due to prior dendritic retraction or T-induced regrowth per se. Instead, the presence of high-normal levels of T prevents dendritic retraction induced by contralateral motoneuron depletion.

Related Products: CTB-SAP (Cat. #IT-14)

Combined bilateral perforant path lesions with lesions of the cholinergic system: an ultrastructural immunogold analysis of nmdar1 representation within the dentate gyrus

Janssen WG, Andrews G, Tomey MI, Baxter MG, Morrison JH (2003) Combined bilateral perforant path lesions with lesions of the cholinergic system: an ultrastructural immunogold analysis of nmdar1 representation within the dentate gyrus. Neuroscience 2003 Abstracts 676.26. Society for Neuroscience, New Orleans, LA.

Summary: Alzheimer’s disease is characterized by deterioration of cholinergic input to the hippocampus, as well as degeneration of input from the entorhinal cortex to the dentate gyrus(DG). Studies have demonstrated an upregulation of the NMDA receptor subunit, NR1, following unilateral ablatement of the perforant path(pp). We hypothesized that cholinergic innervation might be essential for DG plasticity following pp ablation. Our study was designed to investigate the synaptic distribution of NR1 following combined 192 IgG-Saporin lesions of the medial septum/vertical diagonal band(MS/VDB) and bilateral(bilat) pp knife cut ablation. Animals received bilat-pp lesions 2-3 weeks days post MS/VDB and were sacrificed 17 days following pp lesion. Four groups of rats were tested: 1)MS-VDB with sham bilat-pp; 2)sham MS-VDB with bilat-pp; 3)MS-VDB with bilat-pp; 4)sham MS-VDB with sham bilat-pp. Using postembedding immunogold electron microscopy and SynBin, a program designed for quantification and compartmentalization of immunogold particles at the synaptic level, we investigated these effects in the outer molecular layer of the DG in a pilot study with 2 animals/group. Initial results suggest that the synaptic pools of NR1 within post-synaptic compartments were not affected with single MS/VDB, but that a long term synaptic down regulation of NR1 follows bilat pp lesion that is not affected by the additional removal of cholinergic input. While these combined lesions do not alter the pattern of synaptic NR1 receptor distribution following pp lesions, these data has important implications for lesion-induced hippocampal plasticity as well as structural and functional recovery.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Medial septal and entorhinal cortical involvement in hippocampal theta rhythm

Yoder RM, Pang KCH (2003) Medial septal and entorhinal cortical involvement in hippocampal theta rhythm. Neuroscience 2003 Abstracts 719.19. Society for Neuroscience, New Orleans, LA.

Summary: Hippocampal theta rhythm (HPCΘ) may be involved in various phenomena, including attention and the acquisition of sensory information. Two projections to HPC, the medial septum-diagonal band of Broca (MSDB) and entorhinal cortex (EC), are involved in the activation or synchronization of HPCΘ. MSDB contains excitatory (cholinergic) and inhibitory (GABAergic) hippocampal projections via the fimbria/fornix. EC contains excitatory (glutamatergic) hippocampal projections via the perforant path (PP). MSDB GABAergic, MSDB cholinergic, or bilateral PP lesions eliminate HPCΘ during urethane anesthesia (HPCΘ-II). In unanesthetized recordings, each of these lesions reduced but did not eliminate HPCΘ during locomotion (HPCΘ-I); MSDB cholinergic and EC lesions caused similar reductions in HPCΘ, and MSDB GABAergic lesions produced a greater amplitude reduction. In an attempt to determine whether interactions exist between MSDB projections and EC, we examined the effects of MSDB GABAergic or cholinergic lesions combined with PP lesions on HPCΘ-I. MSDB GABAergic and cholinergic lesions were produced by intraseptal injection of kainic acid and 192 IgG-saporin, respectively. Bilateral PP lesions were produced by passing cathodal current through an electrode located in the medial PP. HPCΘ amplitude was calculated as the square root of power at peak frequency (Fourier analysis) within the HPCΘ range. The combination of MSDB GABAergic and PP lesions eliminated HPCΘ-I. The combination of MSDB cholinergic and PP lesions did not reduce HPCΘ-I amplitude further than MSDB cholinergic or PP lesions alone. These results suggest the inhibitory (MSDB GABAergic) and excitatory (MSDB cholinergic or EC glutamatergic) projections interact to support HPCΘ-I. Furthermore, MSDB cholinergic and EC glutamatergic projections may be redundant for HPCΘ-I.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Normalization of burn-induced hypermetabolism following 3rd ventricle injection of saporin-CRF conjugate

Chance WT, Dayal R, Friend LA, Sheriff S (2003) Normalization of burn-induced hypermetabolism following 3rd ventricle injection of saporin-CRF conjugate. Neuroscience 2003 Abstracts 614.5. Society for Neuroscience, New Orleans, LA.

Summary: The development of hypermetabolism following major burn trauma presents significant problems for patient management and recovery. To better understand CNS mediation of burn-induced hypermetabolism, we disrupted CRF neurotransmission by injecting a conjugate of CRF to the ribosome toxin, saporin, into the 3rd ventricle of burned and control rats. Following anesthetization (ketamine/xylazine; 80/15 mg/kg), cannulae (24 ga) were implanted into the 3rd ventricle of 58 adult, male, SD rats. Two weeks later, these rats were anesthetized again and subjected either to a 25 sec, open-flame, full-thickness burn or sham-burn procedures. One week later, the rats were divided into groups to receive ivt injections of artificial CSF (5 ul), saporin (2.5 ug) or saporin-CRF (2.5 ug). Resting energy expenditure (REE) was determined by indirect calorimetry for 60 min on all rats 14 days post-burn. Burned rats treated with CSF exhibited significantly (p<0.01) increased REE (164 ± 4 vs 132 ± 7 kcal/kg/day). Although the saporin treatment had no effect in burned (175 ± 6 kcal/kg/day) or sham-burned (133 ± 10 kcal/kg/day) rats, REE was reduced (p<0.01)in the burned rats treated with the saporin-CRF conjugate (145 ± 6 kcal/kg/day). CRF-induced (1 ug) increase in REE was also prevented in saporin-CRF-treated sham-burned rats. Determination of hypothalamic CRF receptor mRNA by RT-PCR suggested that CRF-R2 expression was reduced in saporin-CRF-treated rats, while CRF-R1 expression was not affected. These results suggest that hypothalamic CRF activity is involved in the maintenance of burn-induced hypermetabolism, and the CRF-2 receptor is important for the expression of this increase in REE. Therefore, control of hypermetabolism may be possible using selective CRF-R2 antagonists.

Related Products: CRF-SAP (Cat. #IT-13)

2-deoxy-D-glucose (2DG) increases NPY mRNA expression in hindbrain neurons

Li AJ, Ritter S (2003) 2-deoxy-D-glucose (2DG) increases NPY mRNA expression in hindbrain neurons. Neuroscience 2003 Abstracts 615.7. Society for Neuroscience, New Orleans, LA.

Summary: Previous results suggest that the orexigenic peptide, neuropeptide Y (NPY), participates in glucoprivic feeding. NPY mRNA in the hypothalamus is increased by glucoprivation (Sergeyev et al, 2000; Fraley and Ritter, 2003) and injection of anti-NPY antibody into the paraventricular nucleus of the hypothalamus (PVH) impairs glucoprivic feeding (He and Edwards, 1998). The hypothalamus is innervated by both arcuate and hindbrain NPY cell bodies. NPY innervation from the hindbrain is substantial and is derived largely or entirely from cell bodies that co-express norepinephrine or epinephrine. Selective immunotoxin lesions have demonstrated that these hindbrain catecholamine neurons are required for glucoprivic feeding (Ritter et al., 2001), as well as for glucoprivic stimulation of corticosterone secretion (Ritter et al., 2003) and suppression of estrus (I'Anson et al., 2003). However, the specific contribution of hindbrain NPY to these glucoregulatory responses has not been examined. Therefore, we examined NPY mRNA expression in hindbrain catecholamine cell groups 1.5 hr after 2-deoxy-D-glucose (2DG, 250 mg/kg) injection using in situ hybridization. Cell groups A1, A1/C1, the middle portion of C1 and C2, showed a basal level of NPY mRNA signal that was dramatically increased by 2DG. In rostral C1 and in C3, where basal NPY mRNA expression was below detection threshold, the hybridization signal was also significantly increased by 2DG. In cell groups A2, A5, A6 and A7, neither basal nor 2DG-stimulated NPY mRNA expression was detected. PVH microinjection of the retrogradely transported catecholamine immunotoxin, saporin conjugated to anti-dopamine-β-hydroxylase, destroyed hindbrain catecholamine neurons and abolished basal and 2DG-stimulated increases in NPY expression in hindbrain cell groups. These data suggest that hindbrain NPY neurons with projections to the hypothalamus participate in glucoprivic feeding and other glucoregulatory responses.

Related Products: NPY-SAP (Cat. #IT-28)

Relationship between CSF hypocretin levels and hypocretin neuronal loss

Gerashchenko D, Murillo-Rodriguez E, Lin L, Xu M, Hallett L, Nishino S, Mignot E, Shiromani PJ (2003) Relationship between CSF hypocretin levels and hypocretin neuronal loss. Neuroscience 2003 Abstracts 616.2. Society for Neuroscience, New Orleans, LA.

Summary: In the sleep disorder narcolepsy there is a massive reduction in the number of neurons containing the neuropeptide, hypocretin (HCRT). Most narcoleptic patients also have low to negligible levels of HCRT in the cerebrospinal fluid (CSF). However, the relationship between HCRT neurons and HCRT levels is not known, making it difficult for investigators to estimate how many HCRT-containing neurons might be present based on measurements of CSF HCRT levels. A relationship between neuronal loss and CSF levels of the ligand is known in other degenerative diseases, such as Parkinson's, but not in narcolepsy. To identify this relationship, hypocretin-2-saporin, the neurotoxin that kills hypocretin neurons, or saline were administered to the lateral hypothalamus and CSF was extracted at zeitgeber times (ZT) 0 (time of lights-on) or ZT 8 at various intervals (2, 4, 6, 12, 21, 36, 60 days) after the neurotoxin administration. Compared to saline animals (n=8), rats with an average loss of 73% of HCRT neurons (n=9) had a 50% decline in CSF HCRT levels on day 60. The decline in HCRT levels was evident by day 6 and there was no recovery or further decrease. The decline in HCRT was correlated with increased REM sleep. Rats with an average loss of 14.4% of HCRT neurons (n=4) showed no significant decline in CSF HCRT levels compared to saline rats. In rats with 73% loss of HCRT neurons, the HCRT levels were not substantially increased by 6h prolonged wakefulness indicating that surviving neurons were not able to increase the output of HCRT to compensate for the HCRT neuronal loss. From these data we conclude that since most narcoleptics have more than 80% reduction of CSF HCRT that in these patients most HCRT neurons are lost.

Related Products: Orexin-B-SAP (Cat. #IT-20)

Sleep deprivation impairs retention performance on an olfactory discrimination task

Pan S, Borowski T, de Lacalle S (2003) Sleep deprivation impairs retention performance on an olfactory discrimination task. Neuroscience 2003 Abstracts 616.21. Society for Neuroscience, New Orleans, LA.

Summary: Sleep deprivation is known to adversely affect learning and memory. We examined the effects of sleep deprivation on attentional and memory processes in rats that received unilateral cholinergic lesions with 192IgG-saporin. Young Fisher 344 male rats were evaluated on an olfactory discrimination learning task both before and after exposure to 8 hours of sleep deprivation. Prior to testing, rats were trained to associate a particular scent with a food reward. They were then tested on their ability to successfully distinguish between two randomly placed, differently scented cups to retrieve the food reward. On a second experiment we investigated the effect that chronic estrogen administration may exert on the cognitive response to sleep deprivation. Gonadectomized rats were implanted s.c. with a pellet containing estrogen or placebo, and tested before and after sleep deprivation, one month after treatment. Untreated rats displayed impaired performance on the retention of the olfactory discrimination task; sleep deprivation resulted in an inability to remember the association of the baited scent from the previous day of testing. However, hormonal treatment appeared to have no significant effect on olfactory discrimination performance. These findings suggest a beneficial effect of sleep in learning and memory. Further research is needed to unravel the role of steroid hormones in modulating sleep-deprived learning deficits in rodents.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Ventral tegmental area lesions alter EEG power spectrum across the sleep/wake cycle

Lee R, Gallegos RA, Crawford EF, Wills DN, Zhukov VI, Huitron-Resendiz S, Criado JR, Henriksen SJ (2003) Ventral tegmental area lesions alter EEG power spectrum across the sleep/wake cycle. Neuroscience 2003 Abstracts 616.5. Society for Neuroscience, New Orleans, LA.

Summary: The ventral tegmental area (VTA) has long been implicated in reward and drug abuse. We previously demonstrated (Lee et al, J. Neurosci. 2001) a role for VTA GABAergic neurotransmission in REM sleep. In continuing studies the potential role of the VTA in modulating electroencephalogram (EEG) activation was explored by selectively lesioning mu-opioid receptor expressing cells, or NMDA-lesioning cells, in the VTA. Under sodium pentobarbital anesthesia rats received either (1) a sham operation (2) a saporin injection (3) an injection of a dermorphin-saporin (DERM-SAP) conjugate (Advanced Targeting Systems, San Diego, CA) (4) or a bilateral VTA injection of NMDA. All injections were delivered in a volume of 0.5 to 1.0 µL over 4 to 8 minutes. Animals were also implanted with electrodes for recording the EEG & EMG. The filtered EEG & EMG were recorded continuously for 24 hours beginning 21 days after surgery. Frequency analysis of the EEG in 15-sec epochs revealed differences in the distribution of relative power in the DERM-SAP or NMDA-lesioned animals, compared to controls. Higher frequency components (12-25 Hz) were reduced in DERM-SAP lesioned animals during waking and slow wave sleep. Histology demonstrated gliosis of GAD-stained neurons in the VTA 3 to 4 weeks after injection of DERM-SAP. These data suggest that long-projecting GABA neurons of the VTA have a desynchronizing influence on cortical EEG arousal mechanisms. This is supported by anatomical evidence of both direct and indirect non-thalamic GABAergic projections to widespread areas of cortex in the rodent. Supported by: DA08301 to SJH.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

A novel nitrate ester enhances performance in a spatial memory task in rats with forebrain cholinergic depletion

Reynolds JN, Sutherland JM, Sutherland RJ (2003) A novel nitrate ester enhances performance in a spatial memory task in rats with forebrain cholinergic depletion. Neuroscience 2003 Abstracts 626.11. Society for Neuroscience, New Orleans, LA.

Summary: Forebrain acetylcholine (ACh) depletion is associated with a variety of cognitive problems, including memory deficits. Here we evaluate the efficacy of a novel nitrate ester, GT 1061, a potential cognition enhancer, in reversing the memory deficit produced by ACh depletion. Long-Evans hooded rats were stereotaxically injected with 192-IgG-saporin intraventricularly or into basal forebrain cell regions to effect loss of cholinergic cells in the basal forebrain and depletion of cholinergic input to neocortex and hippocampus. The rats were postoperatively tested in a version of the Morris water task in which the location of the hidden platform was changed every second day. This version allows for repeated testing of new spatial learning and 24-hr memory retention. ACh depletion causes statistically reliable deficits in new learning and retention components of the task. We examined the effects of oral (0.5, 1, 5, and 10 mg/kg) and intraperitoneally injected (1, 10, 25 and 50 mg/kg) GT 1061 and donepezil oral (0.05, 0.5, 0.1, 1 mg/kg) and intraperitoneal (0.5 mg/kg) on performance of ACh depleted rats. Both oral and injected GT1061 (10 mg/kg oral, and 1 mg/kg i.p.) and donepezil improved new learning and retention performance. The improvement was especially evident during the 24-hr retention tests when GT1061 treated rats performed as well as normal rats. On this measure 10 mg/kg GT 1061 and 1 mg/kg donepezil administered orally were equipotent.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Impairments of working memory processes on a model of Alzheimer’s disease in monkeys

Dudkin KN, Chueva IV, Makarov FN, Beach TG, Roher AE (2003) Impairments of working memory processes on a model of Alzheimer’s disease in monkeys. Neuroscience 2003 Abstracts 626.8. Society for Neuroscience, New Orleans, LA.

Summary: We have investigated the characteristics of visual working memory in a delayed-discrimination task in a model of Alzheimer’s disease (AD) in rhesus monkeys. Three animals received unilateral stereotaxic intracerebroventricular injection of the nucleus basalis of Meynert and three monkeys received sterile saline injections and thus served as controls. The lesioning agent consisted of a ribosomal toxin, saporin, conjugated to monoclonal antibodies against (the nbM lesion) the p75 neurotrophin receptor (p75NTR), which is expressed almost exclusively on cholinergic neurons of the nbM. The rationale for the model is the same as for a rabbit model of AD (Roher et al, Ann. NY Acad Sci. 2000). The monkeys were trained to discriminate stimuli with different types of visual information (spatial frequency gratings, color, spatial choice, spatial relationships between components of objects). The data obtained demonstrate that the nbM lesioning agent had a weak effect on visual differentiation without delay (long-term memory), but significantly decreased the duration of information storage (by a factor of 2 – 3) in working memory later two months after injection. These changes depended on temporal stage after injection and stimulus properties, and were accompanied by increase of motor reaction time and of refusal of task decision. In monkeys that were sham injected, there were no alterations in working memory characteristics. The results suggest that considerable worsening of the working memory characteristics for monkeys after lesion of the nbM reflects the formation of an AD model in these monkeys. The principles of functional organization of working memory and role of pathology of the cortical mechanisms in an impairment of memory characteristics are discussed.

Related Products: ME20.4-SAP (Cat. #IT-15)

Cholinergic deafferentation increases expression of the glur-1 subunit of the AMPA receptor in frontal cortex of young adult but not aging rats

Kim I, Wilson RE, Wellman CL (2003) Cholinergic deafferentation increases expression of the glur-1 subunit of the AMPA receptor in frontal cortex of young adult but not aging rats. Neuroscience 2003 Abstracts 633.9. Society for Neuroscience, New Orleans, LA.

Summary: Previously, we demonstrated that plasticity of frontal cortex is altered in aging rats: cholinergic lesions of the nucleus basalis magnocellularis (NBM) produce larger declines in dendritic morphology in frontal cortex of aged rats compared to young adults. In addition, these lesions result in upregulation of dendritic spines in frontal cortex of young adult but not aging rats. To begin to identify possible mechanisms underlying age-related differences in plasticity after NBM lesion, we assessed immunohistochemical labeling of the AMPA receptor subunit GluR1 in young adult and aging rats after either sham or 192 IgG saporin lesions of the NBM. Young adult (N=17), middle-aged (N=16), and aged rats (N=13) received unilateral sham or 192 IgG saporin lesions of the NBM. Two weeks later, brains were processed for immunohistochemical labeling of the GluR1 subunit of the AMPA receptor. An unbiased stereological technique was used to estimate density of labeled neurons in layer II-III of frontal cortex. Cells were identified as neurons based on standard morphological criteria and counted. Using a computerized image analysis system interfaced with a microscope, the average optical density of the white matter below frontal cortex was determined; neurons with optical densities at least one standard deviation above this mean were identified as intensely labeled. In young adult rats, lesions produced a 55% increase in the density of intensely GluR1-immunopositive neurons in frontal cortex. On the other hand, lesions had no effect on counts of GluR1-immunoreactive neurons in middle-aged and aged rats. This age-related difference in lesion-induced expression of AMPA receptor subunit protein could underlie the age-related differences in dendritic plasticity after NBM lesions.

Related Products: 192-IgG-SAP (Cat. #IT-01)

The effects of IgG-192-saporin lesions of limbic forebrain on rat cocaine self-administration

Co C, Yin X, Johnson WE, Martin TJ, Smith JE (2003) The effects of IgG-192-saporin lesions of limbic forebrain on rat cocaine self-administration. Neuroscience 2003 Abstracts 422.3. Society for Neuroscience, New Orleans, LA.

Summary: The involvement of cholinergic neurons in cocaine self-administration has been recently demonstrated. This study was undertaken to further assess the role of cholinergic innervations of/ or interneurons in limbic brain regions previously shown to receive enhanced dopamine input during cocaine self-administration. Rats were trained to self-administer cocaine on an FR2 schedule using a within session dose intake procedure (3½ hour session with 1 hour access each to 0.17, 0.33 and 0.67 mg/infusion). The doses were then decreased systematically to threshold levels where only the highest dose was self-administered during the session. The cholinergic neurotoxin IgG-192-saporin (0.25 µg in 1 µl) or vehicle was then bilaterally administered into the posterior nucleus accumbens (NAcc) - ventral pallidum (VP). The saporin lesion resulted in a shift to the left in the dose intake relationship for cocaine self-administration with all three doses maintaining responding. The sham-vehicle treated rats continued to only sample the higher dose. Real time RT-PCR was used to assess the magnitude and extent of the lesion. Gene expression for p75 (the target for 192 IgG) and choline acetyltransferase (ChAT) were assessed in the NAcc, VP, caudate nucleus (CP) and diagonal band (DB) of these rats. Significant reductions in p75 and ChAT gene expression were seen in the DB and VP while only small decreases were seen in the NAcc and CP of the saporin treated rats. These data suggest that the overall influence of cholinergic neurons in the DB and VP are inhibitory to the processes underlying cocaine self-administration.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Inhibition within the nucleus tractus solitarius (NTS) ameliorates social deficits due to specific acetylcholine (ACh) or Purkinje cell lesions

Parikh T, Lee S, Walker BR (2003) Inhibition within the nucleus tractus solitarius (NTS) ameliorates social deficits due to specific acetylcholine (ACh) or Purkinje cell lesions. Neuroscience 2003 Abstracts 423.18. Society for Neuroscience, New Orleans, LA.

Summary: Previously, we demonstrated that enhancement of GABA transmission, or blockade of ionotropic glutamate within rat brainstem structures, which mediate limbic-motor seizure control, attenuated behavioral deficits, which were similar to those seen in human patients with autism, due to developmental cerebellum lesions. Evidence suggests that within autism spectrum disorders, there is a decrease in cholinergic neurons in the forebrain and/or a loss of purkinje cells in the cerebellum which might account for these behavioral deficits. Therefore, in the present study, we tested the hypothesis that specific lesions to the rat ACh system or reduction of purkinje cells in the rat cerebellum would lead to specific alterations of social behavior. Furthermore, alterations in GABA and glutamate transmission within the NTS would correct these social deficits. We examined the effect of ACh or purkinje cell lesions on social behavior in rats by recording social interactions before and after bilateral saporin injections (192-IgG or OX-7; 2 µg/side). As compared to preinjection behavior, saporin injections decreased social interaction of adult rats. Bilateral microinjections of the GABA agonist muscimol (256 pmol) into the mNTS at least 10 minutes prior to behavioral testing returned the amount of social investigation of the lesioned animals to pre-saporin levels. These findings suggest that specific neuronal populations are responsible for mediating social behavior in rats, and that there is a functional connection between those systems and the brainstem structures utilized for seizure control.

Related Products: 192-IgG-SAP (Cat. #IT-01), OX7-SAP (Cat. #IT-02)

Selective cholinergic lesion of the medial septum impairs retention but not acquisition of a passive avoidance memory task

Ukairo OT, Arshad S, Gibbs RB, Johnson DA (2003) Selective cholinergic lesion of the medial septum impairs retention but not acquisition of a passive avoidance memory task. Neuroscience 2003 Abstracts 425.16. Society for Neuroscience, New Orleans, LA.

Summary: Infusion of 192 IgG-saporin (SAP) into the medial septum (MS) selectively destroys cholinergic neurons projecting to the hippocampus. This study examined the effect of such lesions on acquisition and retention using a passive avoidance paradigm. Male Sprague-Dawley rats received either SAP (.22 μg in 1 μl) or vehicle directly into the MS. Passive avoidance training began two weeks later. Training consisted of placing an animal into the lighted chamber of the apparatus and then delivering footshock (.75 mA, 1 sec.) when the animal moved into the adjacent darkened chamber. Training was repeated until animals avoided the dark chamber for 2 consecutive trials of 5 min. duration. Retention (latency to enter the dark chamber) was tested 1 week later. Results showed no effect of SAP lesion on the number of trials necessary to acquire avoidance behavior. In contrast, SAP-lesioned animals showed a significant impairment in retention, as evidenced by a 72% decrease in crossover latency one week following training. These results suggest that selective destruction of cholinergic septo-hippocampal projections impairs retention, but not acquisition, of passive avoidance behavior to aversive stimuli.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Arousal enhances delayed match to position T-maze performance independent of septo-hippocampal cholinergic projections

Fitz NF, Gibbs RB, Johnson DA (2003) Arousal enhances delayed match to position T-maze performance independent of septo-hippocampal cholinergic projections. Neuroscience 2003 Abstracts 425.17. Society for Neuroscience, New Orleans, LA.

Summary: Infusion of the selective cholinergic immunotoxin, 192 IgG-saporin (SAP) into the medial septum (MS) of rats selectively lesions cholinergic neurons projecting to the hippocampus and impairs acquisition of a delayed matching to position (DMP) T-maze task. The intent of the present study was to determine if enhanced performance associated with arousal is dependent on septo-hippocampal cholinergic projections. Male Sprague-Dawley rats received MS infusions of SAP 0.22 µg in 1µl or vehicle. Fourteen days later, animals were trained on the DMP spatial memory task. SAP and control animals were randomized into an “arousal” group that was injected with saline (IP; 1 ml/Kg) 30 min before testing each day or a “non-arousal” group that was not. SAP lesions significantly impaired acquisition of the DMP task in both the arousal and non-arousal groups. Conversely, arousal significantly enhanced acquisition in both control and SAP lesioned rats. There was no significant interaction between the effects of cholinergic lesions and arousal. These results suggest that septo-hippocampal cholinergic projections are not engaged in enhanced spatial learning mediated by arousal.

Related Products: 192-IgG-SAP (Cat. #IT-01)

192 IgG-saporin lesions of the nucleus basalis magnocellularis in rats fail to disrupt acquisition or retention of differential reinforcement of low rate responding

Butt AE, Corley S, Cabrera S, Chavez C, Kitto M, Ochetti D, Renovato A, Salley T, Sarpong A (2003) 192 IgG-saporin lesions of the nucleus basalis magnocellularis in rats fail to disrupt acquisition or retention of differential reinforcement of low rate responding. Neuroscience 2003 Abstracts 425.5. Society for Neuroscience, New Orleans, LA.

Summary: The frontal cortex has been implicated in supporting timing behavior in tests of differential reinforcement of low rate responding (DRL) in rats. DRL performance is similarly influenced by anticholinergic drugs; scopolamine interferes with DRL performance by increasing the number of nonreinforced responses and thus decreasing DRL efficiency. Because the frontal cortex receives significant cholinergic input from the nucleus basalis magnocellularis (NBM) in rats, we hypothesized that NBM lesions would disrupt DRL performance in the current experiment. Male Long-Evans rats were placed first in a DRL 10 s schedule of reinforcement before advancing to a DRL 20 s schedule. Rats received 50 trials per day for 20 consecutive days on both DRL schedules. When rats reached stable performance, they received either bilateral 192 IgG-saporin lesions of the NBM or sham lesions. Upon recovery, rats were reintroduced to the DRL 20 s task for 10 days of post-operative testing. Finally, rats were tested using a novel delay interval in a DRL 30 s task. Testing continued for 10 additional days. Results showed that the NBM lesion group showed no significant change in either the total number of responses or in DRL efficiency (reinforced responses / total responses) between pre- and post-operative DRL 20 s testing. Subsequent acquisition in the DRL 30 s task was similarly not disrupted by NBM lesions. The effectiveness of the lesions was verified by acetylcholinesterase (AChE) staining, which showed pronounced depletion of cortical AChE with normal AChE-positive staining in the hippocampus and medial septal area. These data suggest that the NBM is not critically involved in either the acquisition or retention of DRL performance.

Related Products: 192-IgG-SAP (Cat. #IT-01)

192-IgG saporin lesions of the medial septum and vertical diagonal band impair cognitive flexibility.

Fletcher BR, Baxter MG, Rapp PR, Shapiro ML (2003) 192-IgG saporin lesions of the medial septum and vertical diagonal band impair cognitive flexibility. Neuroscience 2003 Abstracts 425.8. Society for Neuroscience, New Orleans, LA.

Summary: Learning and memory remain largely intact following selective basal forebrain cholinergic lesions. By comparison, single unit recording studies have documented reliable effects of such lesions, including abnormally rigid hippocampal place fields when animals are confronted with changes in the configuration of the testing environment. The present experiment tested the prediction that cholinergic lesions of the basal forebrain would impair performance of tasks requiring cognitive flexibility. Rats received 192-IgG saporin or control vehicle injections into the medial septal nucleus and vertical diagonal band, and were tested on cued and spatial delayed match-to-place tasks in a radial arm water maze. Test sessions consisted of four sample trials in which animals searched for a cued or hidden escape platform located in a fixed position at the end of one arm (60 sec cutoff, inter-trial interval = 15 sec). A memory delay was imposed by returning rats to the home cage for a variable delay (15 sec. – 6 hrs), followed by two test trials. The lesion and control groups learned at similar rates in both versions of the task, and performed comparably on the critical test trials, independent of the length of the retention interval. However, lesioned rats were impaired during the transition from the cued to spatial variants of testing. Specifically, the lesion group made significantly more errors on an early sample trial in the spatial task, returning to the location that was previously correct during cued training. Pending histological confirmation of the extent and selectivity of the experimental lesions, this pattern of results suggests that damage to the basal forebrain cholinergic system spares spatial learning but impairs cognitive flexibility when task contingencies are changed.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Discrete lesioning of orexin (hypocretin)-containing neurons potentiates dexmedetomidine- but not pentobarbital-induced hypnosis

Nelson LE, Franks NP, Maze M (2003) Discrete lesioning of orexin (hypocretin)-containing neurons potentiates dexmedetomidine- but not pentobarbital-induced hypnosis. Neuroscience 2003 Abstracts 426.13. Society for Neuroscience, New Orleans, LA.

Summary: Introduction: Recent work suggests that anesthetics putatively modulated by the α2-adrenoceptor (e.g. dexmedetomidine (DEX)) or the GABAA receptor (e.g. pentobarbital (PTB)) elevate and depress c-Fos expression, respectively, in the orexinergic perifornical area (PeF)1. Here the hypnotic effects of DEX and PTB are assessed after selective lesion of the PeF by orexin-B conjugated to saporin (OX-SAP). Methodology: Anesthetized Fischer rats were administered stereotaxic PeF injections of saline (0.5µl/side) or OX-SAP (490ng/0.5μl/side; as described2). Loss of righting reflex (LORR) induced by DEX (150μg/kg, SC), PTB (50mg/kg, SC), and saline was tested 1 day pre- and 1, 4, 8, and 12 days post-surgery, then lesions were assessed histologically. All data are presented as means±SEMs (n=6; comparisons by unpaired t-tests and ANOVA, Newman-Keuls). Results: Bilateral PeF lesions enhanced DEX-induced hypnosis at days 8 (281.2±15.8 min; p<0.05) and 12 (322.7±15.93 min; p<0.001) as compared to naïve (234.5±9.0 min) and saline sham animals (day 8, 236.7±9.8 min; day 12, 242.8±10.80 min). In contrast, PTB-induced LORR remained unaffected at day 12 (124.8±6.8 min) relative to naïve (119.4±4.6 min) and sham (120.8±5.3 min). These results agree with previous reports that by day 12, PeF-microinjected OX-SAP induces roughly 80% cell loss2. Conclusion: The absence of a functional PeF potentiates hypnosis induced by DEX but not PTB, as perturbation of the PeF by microinjected GABAA receptor antagonist gabazine is known to 1. References: 1 Nelson et al. (2002) SfN abstract 776.14/M20; 2 Geraschenko et al. (2001) J Neurosci 21:7273-83.

Related Products: OX7-SAP (Cat. #IT-02)

Dendritic dysgenesis in midline cortical regions following selective acetylcholine and dopamine lesions in neonatal rats

Sherren N, Pappas BA (2003) Dendritic dysgenesis in midline cortical regions following selective acetylcholine and dopamine lesions in neonatal rats. Neuroscience 2003 Abstracts 457.11. Society for Neuroscience, New Orleans, LA.

Summary: Both acetylcholine (ACh) and dopamine (DA) afferents reach their cortical targets during periods of synaptogenesis, and are perfectly positioned to influence the cytoarchitectural development of cortical neurons. Thus the behavioural outcomes of these lesions may be related to the development of appropriate dendritic morphology in neurons from cortical regions involved in cognition. Previous studies have either used non-specific lesion techniques or have not examined long-term effects. We lesioned rat pups at P7 with either 600 ng of the selective immunotoxin 192 IgG-saporin, or 150 ug of 6-hydroxydopamine preceded by desmethylimipramine, or both, and aged them to four months. One squad of rats was sacrificed for neurochemistry and another was prepared for morphological analysis using Golgi-Cox stain. The ACh lesion caused a 32% decrease in choline acetyltransferase activity in the frontal/cingulate cortex and a 72% reduction in retrosplenial cortex (RSC). This was associated with reductions in total dendritic length of the apical tree of layer V pyramidal cells in the medial prefrontal cortex (mPFC), the apical tree of layer III pyramidal cells in the anterior cingulate cortex (ACC), and the basal tree of layer III pyramidal cells in RSC. The DA lesion caused a 76% reduction in DA levels in frontal/cingulate cortex and no change in RSC levels. This was associated with reductions in total dendritic length of the basal and apical trees of layer V pyramidal cells in mPFC, and the basal tree of layer III pyramidal cells in ACC. No changes in layer III pyramidal cells were noted in RSC following the DA lesion. These data demonstrate that ascending ACh and DA afferents play a vital role in the cytoarchitectural development of the cortex. This is particularly important considering that hypofunction in these systems is a characteristic feature of neurodevelopmental disorders involving mental retardation, such as Rett and Down syndrome.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Destruction of brainstem catecholamine neurons attenuates somatosympathetic reflex and responses to cholecystokinin

Neale JJ, Goodchild AK, Dampney RAL, Pilowsky PM (2003) Destruction of brainstem catecholamine neurons attenuates somatosympathetic reflex and responses to cholecystokinin. Neuroscience 2003 Abstracts 501.11. Society for Neuroscience, New Orleans, LA.

Summary: The integrity of the rostral ventrolateral medulla (RVLM) is essential for the expression of many sympathetic reflexes and the maintenance of vasomotor tone. The RVLM contains bulbospinal neurons, of which about half are catecholaminergic (C1). Destruction of bulbospinal C1 neurons leads to attenuation or abolition of the sympathetic baroreflex and chemoreflex, respectively. This study examines the effects of such destruction on blood pressure (BP), the somatosympathetic reflex and responses to intravenous (i.v) cholecystokinin (CCK) in urethane-anaesthetised, paralysed and ventilated Sprague-Dawley rats. Eighty percent of the spinally projecting C1 neurons in the RVLM were destroyed by bilateral microinjections of the immunotoxin, anti-DBH-saporin (12ng/100nl), into the intermediolateral cell column of the thoracic spinal cord (T1-2). Following treatment with the neurotoxin, systolic BP was measured for 3-5 weeks before testing the reflexes. No significant changes in systolic BP were observed. In the present study destruction of bulbospinal C1 neurons attenuated the baroreflex, replicating the findings of Schreihofer and Guyenet (2000, Am J Physiol 279:R729-R742). Activation of the somatosympathetic reflex by electrical stimulation of the tibial nerve normally elicits two peaks in averaged splanchnic sympathetic nerve activity. Following destruction of C1 neurons, the threshold voltage was reduced and the second peak was either markedly attenuated or abolished at two times threshold voltage. Intravenous injection of CCK (1, 10 and 100mg/kg) elicited depressor and sympathoinhibitory responses that were significantly reduced following destruction of bulbospinal C1 neurons. These results demonstrate a key role of bulbospinal C1 neurons in the somatosympathetic reflex and the sympathetic responses to i.v CCK but not in the tonic control of blood pressure.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Serotonergic neurons and development: implications for normal brain function and human disease

Richerson GB, Nattie EE, Deneris ES, Lauder JM (2003) Serotonergic neurons and development: implications for normal brain function and human disease. Neuroscience 2003 Abstracts 329. Society for Neuroscience, New Orleans, LA.

Summary: Symposium. Serotonergic neurons have widely divergent projections to virtually all of the CNS, and are involved in a variety of brain functions. This symposium will focus on how dysfunction of 5-HT neurons during development can influence brain function throughout life. G Richerson will discuss pH chemosensitivity of 5-HT neurons, how this changes during development, and the emerging hypothesis that these neurons induce arousal, a feeling of suffocation and hyperventilation in response to increased CO2. E Nattie has used focal manipulations of the raphe in vivo, including cell specific killing with an antibody to the serotonin transporter conjugated to the toxin saporin, to show that dysfunction of 5-HT neurons may lead to a defect in physiologic regulatory processes that are important during development. E Deneris will discuss mutant mice lacking the Pet-1 ETS gene, in which the majority of CNS 5-HT neurons are missing. 25-30% of Pet-1 nulls die during the first postnatal week, which may result from abnormal respiration. Surviving adults display anxiety-like and aggressive behavior. J Lauder will discuss 5-HT as a differentiation signal in prenatal brain development and as a morphogen in craniofacial development. Effects of prenatal exposure to serotonergic drugs or neurotoxins on postnatal outcome will be described. The speakers will introduce new hypotheses about how dysregulation of 5-HT neurons and 5-HT receptors during development may lead to a variety of brain disorders such as SIDS, migraine, autism, panic attacks and anxiety.

Related Products: Anti-SERT-SAP (Cat. #IT-23)

Tuberomammillary nucleus lesion decreases the anticipatory events induced by restricted feeding in rats

Recabarren MP, Valdes JL, Seron-Ferre M, Torrealba F (2003) Tuberomammillary nucleus lesion decreases the anticipatory events induced by restricted feeding in rats. Neuroscience 2003 Abstracts 510.19. Society for Neuroscience, New Orleans, LA.

Summary: Our previous studies indicate that the histamine-containing neurons of the tuberomammillary nucleus (TMN) become active in anticipation to feeding time in rats under a restricted feeding schedule. To assess the role of the TMN in this anticipatory activity in rats, we lesioned the TMN bilaterally with stereotaxic injections of 50ng ORX-SAP (Advanced Targeting System, CA). We analyzed the locomotor activity, core temperature and the feeding frequency exhibited by these animals during a restricted feeding protocol, where food was available between 10:00 h and 12:00 h for at least 2 weeks. Rats were implanted in the abdominal cavity with telemetric sensors (Minimitter, OR) to measure locomotor activity and core temperature. During the whole experiment rats were maintained in individual cages and under controlled photoperiod of 12 hours light and 12 hours dark, light were on at 07:00 h. We analyzed the 3 hours preceding food arrival. We checked the extent of TMN destruction by immunostaining the brain sections with antibody against adenosine diaminase (ADA), which colocalize with histaminergic neurons in the TMN. Control rats were subjected to the same procedures except for the injection of the ORX-SAP toxin. Results: Lesion rats showed a significant decrease in the number of ADA-ir neurons in the TMN, as well as a decreased anticipatory activity under restricted feeding in comparison with control rats. Lesion rats although awake before food arrival, were less eager to feed compared to controls, as assessed by food bin approaches. Control rats were slightly more active than lesion rats during restriction. In conclusion, the functional integrity of the TMN is required for the full expression of the anticipatory events that are stimulated by a restricted feeding schedule.

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Cholinergic deafferentation of the entorhinal cortex in rats impairs encoding of novel but not familiar stimuli in a delayed non-match to sample task (DNMS)

McGaughy JA, Jindal M, Eichenbaum HB, Hasselmo ME (2003) Cholinergic deafferentation of the entorhinal cortex in rats impairs encoding of novel but not familiar stimuli in a delayed non-match to sample task (DNMS). Neuroscience 2003 Abstracts 425.4. Society for Neuroscience, New Orleans, LA.

Summary: Muscarinic cholinergic receptor activation in entorhinal cortex (EC) activates intrinsic depolarizing membrane currents which cause self-sustained spiking activity in single neurons (Klink and Alonso, J. Neurophys. 77, 1997). This effect may underlie delay activity and match-dependent activity changes in delayed match to sample tasks (Fransen et al., J. Neurosci. 22, 2002) and could allow accurate maintenance of novel information without dependence on synaptic modification associated with previous exposure (familiarization). Consistent with this, research in human subjects suggest that the medial temporal lobes are specifically activated during working memory for novel but not familiar stimuli (Stern, et al. Hippocampus v. 11, 2001), and cholinergic deafferentation of the rhinal cortex in non-human primates has been shown to impair memory for trial-unique (novel) stimuli (Turchi et al., SFN abstracts v. 28). The current study tests the hypothesis that cholinergic deafferentation of the EC produces impairments in working memory for novel but not familiar stimuli. Prior to surgery rats were trained in an odor DNMS task with a brief delay. After reaching asymptotic performance, rats were infused with either 192-IgG-saporin (SAP) or its vehicle into the EC (0.01 µg/µl; 1.0 µl/injection; 6 infusions/hemisphere). Rats were not impaired at any delay when tested with familiar odors but showed significant, persistent impairments when tested with novel odors. An increase in task difficulty alone was insufficient to explain these effects. These data support the hypothesis that cholinergic afferents to the EC activate cellular mechanisms of sustained spiking activity necessary for maintenance of novel but not familiar stimuli in a working memory task. Support Contributed By: NIH MH61492, MH60013, DA16454.

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Altered neurogenesis after cholinergic forebrain lesion in the adult rat.

Cooper-Kuhn CM, Winkler J, Kuhn H (2003) Altered neurogenesis after cholinergic forebrain lesion in the adult rat. Neuroscience 2003 Abstracts 348.9. Society for Neuroscience, New Orleans, LA.

Summary: Adult hippocampal neurogenesis has been shown to be functionally connected to learning and memory and at the same time to be regulated by a multitude of extracellular cues, including hormones, growth factors, and neurotransmitters. The cholinergic forebrain system is one of the key transmitter systems for learning and memory. Within the hippocampus and olfactory bulb, two regions of adult neurogenesis, cholinergic innervation is quite extensive. This experiment aims at defining the role of cholinergic input during adult neurogenesis by using an immunotoxic lesion approach. The immunotoxin 192IgG-saporin was infused into the lateral ventricle of adult rats to selectively lesion the cholinergic neurons of the cholinergic basal forebrain (CBF), which project to the dentate gyrus and the olfactory bulb. Five weeks after lesion the rate of neurogenesis declined significantly in the dentate gyrus and olfactory bulb granule cell layers, whereas the generation of neurons in the periglomerular region of the olfactory bulb was unaffected. The number of apoptotic cells increased specifically in the progenitor region of the dentate gyrus as well as in the periglomerular layer of the olfactory bulb. Therefore, one of the possible mechanisms by which acetylcholine could promote neurogenesis is by increasing the survival of progenitor and immature neurons. Neurotransmitters can alter the microenvironment of neural progenitor cells, whether directly or indirectly, and these changes lead to significant alterations in neurogenesis. In principle, the data suggest that acetylcholine is stimulatory to adult hippocampal neurogenesis, since neurotoxin lesions specific to this neurotransmitter system lead to a reduced number of new neurons.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Neuroinflammatory response to mu p75-saporin immunotoxin-induced degeneration of basal forebrain cholinergic neurons

Hunter CL, Quintero EM, Gilstrap L, Bhat NR, Granholm AE (2003) Neuroinflammatory response to mu p75-saporin immunotoxin-induced degeneration of basal forebrain cholinergic neurons. Neuroscience 2003 Abstracts 527.15. Society for Neuroscience, New Orleans, LA.

Summary: Basal forebrain cholinergic neurons, which provide the major cholinergic innervation to the cortical regions and play a key role in the processing of information involved in cognitive processes, degenerate during both normal aging and Alzheimer’s disease. Neuroinflammation, specifically the activation of microglia, is known to affect the progression of neuronal degeneration. Activated microglia produce inflammatory mediators that have neuropathic as well as neuroprotective actions, and it has been suggested that inflammatory mediators produced by activated microglia may play a role in the decline of specific neuronal sub-types in neurodegenerative diseases. The immunotoxin mu p75-SAP has been shown to selectively destroy cholinergic neurons in the basal forebrain of mice, resulting in reduced choline acetyl-transferase activity and cognitive impairments. To characterize the inflammatory response to mu p75-SAP lesions, 3 month-old mice received icv injections of mu p75-SAP (3.6 mg) followed by treatment with an anti-inflammatory agent, minocycline (45 mg/kg i.p.), or saline. Seven days after lesioning, immunohistochemistry was used to analyze markers for cholinergic and non-cholinergic neurons and inflammation. Cholinergic lesioning resulted in a dramatic increase in CD45, a microglial marker, but no change in GFAP, an astroglial marker, in the basal forebrain region. Lesioned animals had elevated levels of phosphorylated p38, a MAP kinase protein involved in inflammatory pathways. Minocycline treatment reduced this inflammatory response. Furthermore, preliminary results suggest that animals treated with minocycline after mu p75-SAP lesioning are partially protected from cholinergic degeneration.

Related Products: mu p75-SAP (Cat. #IT-16)

Selective destruction of MOR expressing dorsal horn neurons using intrathecal dermorphin-saporin.

Wiley RG, Miller SA, Kline IV RH (2003) Selective destruction of MOR expressing dorsal horn neurons using intrathecal dermorphin-saporin. Neuroscience 2003 Abstracts 174.15. Society for Neuroscience, New Orleans, LA.

Summary: Evidence suggests that the mu opiate receptor (MOR) is key to the analgesic action of morphine. In the present study, we sought to determine if a disulfide conjugate of the mu opioid peptide, dermorphin, to the ribosome-inactivating protein, saporin, (derm-sap) would destroy neurons expressing MOR in the substantia gelatinosa (SG) of the spinal cord. Derm-sap was injected into the lumbar subarachnoid space of anesthetized adult, male Sprague-Dawley rats using a catheter inserted through the atlanto-occipital membrane and passed 8 cm caudally. The catheter was removed 15 minutes after toxin injection. Rats were sacrificed after 2 weeks, and 40 um transverse frozen sections of the L4 spinal segment were processed for immunohistochemical demonstration of MOR, NeuN, calbindin D28k, parvalbumin, NK-1R and for Nissl staining. In control rats, beta-funaltrexamine was injected just before derm-sap or derm-sap was pre-treated to reduce the disulfide bond which dissociates the toxin and neuropeptide. MOR staining in the SG was evaluated using quantitative densitometry. Initial experiments revealed a dose-related decrease in MOR staining in the dorsal horn without effect on dorsal root ganglia at doses up to 1000 ng. The maximally tolerated dose of derm-sap (500 ng) selectively decreased MOR staining by 54% as did multilevel lumbar dorsal rhizotomy. Combining 500 ng of derm-sap and multilevel rhizotomy produced 92% loss of MOR staining in the SG. Based on analysis of non-co-localized markers and control experiments, we interpret the results to indicate that intrathecal derm-sap selectively destroys MOR-expressing neurons in the SG without toxicity to primary afferents. This lesion will be useful in analysis of opioid mechanisms in the dorsal horn.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

SSP-saporin decreases formalin induced c-Fos expression throughout the dorsal horn.

Kline IV RH, Wiley RG (2003) SSP-saporin decreases formalin induced c-Fos expression throughout the dorsal horn. Neuroscience 2003 Abstracts 174.7. Society for Neuroscience, New Orleans, LA.

Summary: Substance P (SP) antagonists and SP-saporin have been shown to decrease phase II of the formalin test suggesting an important role for SP in this model of persistent pain. SP antagonists also decrease formalin induced c-fos expression in dorsal horn neurons. A congener of SP-sap that is more stable and has higher affinity for NK-1R, SSP-sap (Sar9Met(02)11-substance P-saporin) has been studied by injection into the striatum and hippocampus where it was more potent and specific than SP-sap. In the present study, this selective and more potent toxin was used to determine the effects of destroying dorsal horn NK-1R on behavior and c-fos induction after intraplantar formalin. Twelve Sprague Dawley male rats were injected intrathecally with 100ng SSP-sap or PBS. After 2 weeks survival, rats underwent hindpaw formalin injections and behavioral scoring, and then were sacrificed after 3 hours and the lumbar spinal cords processed for immunohistochemical demonstration of NK-1R and c-fos. There were significant correlations between the loss of superficial laminae NK-1R neurons, decreased formalin behavior and dorsal horn c-fos expression. Therefore lumbar i.t. SSP-sap 1) decreased NK-1R cells in laminae I but not in the deeper laminae 2) decreased phase II formalin behavior 3) decreased c-fos in both the superficial and deep laminae. Since c-fos expression in the deeper laminae was decreased and NK-1R was spared in these laminae, we conclude that a lesion affecting only laminae I NK-1R lesion alters activation of neurons throughout the dorsal horn suggesting a key role for the missing neurons in the transfer of nociceptive inputs to deeper laminae.

Related Products: SSP-SAP (Cat. #IT-11)

A single rostral ventromedial medulla (RVM) treatment with cholecystokinin-saporin (CCK-sap) prevents the development of opioid-induced paradoxical pain and spinal morphine antinociceptive tolerance

Xie Y, Vanderah TW, Ossipov MH, Lai J, Porreca F (2003) A single rostral ventromedial medulla (RVM) treatment with cholecystokinin-saporin (CCK-sap) prevents the development of opioid-induced paradoxical pain and spinal morphine antinociceptive tolerance. Neuroscience 2003 Abstracts 177.4. Society for Neuroscience, New Orleans, LA.

Summary: Sustained morphine elicits tactile and thermal hypersensitivity (opioid-induced paradoxical pain) and antinociceptive tolerance which are mediated through the time-dependent activation of descending facilitation from the RVM. With morphine exposure, CCK expression and/or release may be altered to activate pain facilitatory neurons of the RVM, manifesting as diminished spinal morphine antinociception (antinociceptive tolerance). To explore a possible role of RVM CCK in morphine-induced paradoxical pain and tolerance, CCK-SAP conjugate was used to selectively lesioned RVM neurons expressing CCK receptors. Male S-D rats received a single RVM injection of CCK, SAP or CCK-SAP. Behavioral responses to tactile (von Frey) and thermal (radiant heat) stimuli were normal 3,7,14 and 28 days after injection. RVM CCK microinjection produced tactile and thermal hypersensitivity in uninjured rats 28 days after receiving RVM CCK or SAP, but not in those receiving CCK-SAP, suggesting the probable loss of RVM CCK receptor-expressing cells. 28 days after RVM CCK, SAP or CCK-SAP injections, rats were implanted with placebo or morphine pellets. Morphine pelleted rats pretreated with RVM CCK or SAP developed tactile and thermal hypersensitivity and spinal antinociceptive tolerance. In contrast, animals pretreated with RVM CCK-SAP did not show morphine induced tactile or thermal hypersensitivity and antinociceptive tolerance was not present. Moreover, CCK-SAP, but not CCK or SAP, pretreatment significantly attenuated the antinociceptive effect of RVM morphine. This suggests that RVM CCK activates tonic descending facilitation driving morphine-induced abnormal pain and spinal antinociceptive tolerance. Moreover, these results suggest the possibility that CCK and opioid receptors may colocalize on some RVM neurons which may act to facilitate pain transmission.

Related Products: CCK-SAP (Cat. #IT-31)

Selective elimination of mu-opioid receptor expressing neurons in the rostral ventromedial medulla (RVM) does not affect periaqueductal gray (pag) stimulation-produced analgesia

Harasawa I, Lai J, Porreca F, Fields HL, Meng ID (2003) Selective elimination of mu-opioid receptor expressing neurons in the rostral ventromedial medulla (RVM) does not affect periaqueductal gray (pag) stimulation-produced analgesia. Neuroscience 2003 Abstracts 177.5. Society for Neuroscience, New Orleans, LA.

Summary: PAG stimulation produces antinociception at spinal levels by modulating RVM neuronal activity. Microinjection of saporin conjugated with the mu-opioid receptor agonist dermorphin (DERM-SAP) into the RVM selectively eliminates MOR expressing neurons and diminishes neuropathic pain symptoms (Porreca et al., 2001). The aim of the present study was to determine whether MOR expressing neurons in the RVM are required for PAG stimulation produced analgesia (PAG/SPA). The minimum electrical current required to inhibit the tail flick response was compared in barbiturate-anesthetized rats given a single RVM injection of SAP or DERM-SAP 3-4 weeks prior to testing. Thresholds in SAP and DERM-SAP treated rats were not different. Furthermore, microinjection of the glutamate receptor antagonist kynurenic acid (10 mM, 800 nl) into the RVM disrupted PAG/SPA in both SAP and DERM-SAP treated rats. These results indicate that 1) mu-receptor expressing neurons in the RVM are not necessary for PAG/SPA, and 2) excitatory amino acid transmission in the RVM is critical for PAG/SPA. In additional experiments, inhibition of neurotransmitter release in the RVM by the microinjection of cobalt chloride (CoCl2, 100 mM, 800 nl), produced significant antinociception only in DERM-SAP treated rats. This finding suggests that DERM-SAP injections result in increased tonic inhibition of RVM neurons and that CoCl2 disinhibits these neurons to produce antinociception. Tonic inhibition of off-cells would account for our failure to find off-cells in DERM-SAP treated rats.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Cholinergic activity enhances hippocampal CA1 long-term potentiation during walking in rats

Leung LS, Shen B, Ma J, Rajakumar N (2003) Cholinergic activity enhances hippocampal CA1 long-term potentiation during walking in rats. Neuroscience 2003 Abstracts 255.5. Society for Neuroscience, New Orleans, LA.

Summary: Long-term potentiation (LTP) at the basal dendrites of CA1 pyramidal cells was induced by a single 200-Hz stimulation train (0.5-1 sec duration) in freely behaving rats during one of four behavioral states - awake-immobility (IMM), walking, slow-wave sleep (SWS) and rapid-eye-movement sleep (REMS). Field excitatory postsynaptic potentials (fEPSPs) generated by basal dendritic excitation of CA1 were recorded before and up to 20 hours after the tetanus. Following a tetanus during any behavioral state, basal dendritic LTP was > 170% of the baseline for the first 30 min after the tetanus and decayed to ~125% at 20 hours after. LTP induced during walking was significantly larger than that induced during IMM, SWS or REMS. LTP induced during IMM, SWS and REMS was not significantly different from each other. To test the hypothesis that septohippocampal cholinergic activity enhanced LTP during walking than during immobility, rats were either pretreated with muscarinic cholinergic antagonist scopolamine (5 mg/kg i.p.) or given selective cholinotoxin IgG192-saporin in the medial septum. Pretreatment with scopolamine decreased the LTP induced during walking but did not affect that induced during IMM, such that the difference between LTP induced during walking and IMM was abolished. In IgG192-saporin injected rats, there was no difference in the LTP induced during walking and during IMM, and scopolamine did not reduce the LTP induced during walking. In contrast, sham-lesioned rats, like other control rats, showed larger LTP induced during walking than during IMM, and LTP induced during walking was attenuated by scopolamine. This appears to be the first demonstration of an enhancement of hippocampal LTP by physiologically activated septal cholinergic inputs. LTP of the CA3 to CA1 synapses may serve important behavioral functions.

Related Products: 192-IgG-SAP (Cat. #IT-01)

H3 receptor antagonists modulate behaviour in a visual spatial attention task in rats with selective lesions of the nucleus basalis magnocellularis

Muir JL, Harrison FE (2003) H3 receptor antagonists modulate behaviour in a visual spatial attention task in rats with selective lesions of the nucleus basalis magnocellularis. Neuroscience 2003 Abstracts 296.7. Society for Neuroscience, New Orleans, LA.

Summary: It is well known that the cholinergic system suffers a large amount of damage in Alzheimer’s Disease (AD). The histaminergic system is known to interact with the cholinergic system but is thought to be largely spared in AD. Compounds which affect histaminergic transmission therefore offer a new further therapeutic avenue to be considered. The effects of two selective H3 receptor antagonists, Thioperamide (1.0, 3.0, 10.0mg/kg) and Ciproxifan (1.5, 3.0, 5.0mg/kg), were investigated for their ability to modulate visual spatial attention using the Five Choice Serial Reaction Time Task. The animal model used was that of cholinergic lesions of the nucleus basalis Magnocellularis (nbM) in the basal forebrain using the selective immunotoxin IgG Saporin. Thioperamide, without affecting overall accuracy, showed very strong trends towards a reduction in anticipatory responses in both sham and lesion groups and also showed a slight reduction in perseverative responses. The more potent Ciproxifan showed no overall change in accuracy but led to a reduction in the anticipatory responses in nbM lesioned animals at all three doses of the drug, returning them to equivalent levels of responses to the sham group. This effect was independent of any overall decrease in activity levels as there were no concomitant changes in response latencies or number of trials completed. Hence these pharmacological manipulations reduced the levels of impulse behaviours manifest by lesioned animals.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Production and characterization of biotinylated gonadotropin-releasing hormone analogs conjugated to avidinylated saporin

Miller BT, Collins TJ (2003) Production and characterization of biotinylated gonadotropin-releasing hormone analogs conjugated to avidinylated saporin. Neuroscience 2003 Abstracts 325.15. Society for Neuroscience, New Orleans, LA.

Summary: Saporin is a potent protein cytotoxin derived from the seeds of the plant Saponaria officinalis. Although unmodified saporin cannot permeate cellular membranes in appreciable amounts, this toxin can be chemically conjugated to various compounds that can enter cells by receptor-mediated uptake. When such conjugates are internalized, saporin can exert a lethal effect by inactivating cellular ribosomes. Thus, when conjugated to compounds that bind to specific cellular receptors, saporin can potentially be used as a relatively precise, targeted toxin. A major challenge in employing saporin-based technologies resides in the construction of conjugates of saporin and various receptor-binding biomolecules. Linking a small, bioactive peptide to saporin must be carried out in such a way as to retain the specific receptor-binding properties of the peptide. Although the successful direct conjugation of a small number of bioactive peptides to saporin has been reported, not all such conjugate preparations are necessarily homogeneous. In theory, the recent commercial availability of avidinylated saporin could allow investigators to utilize the numerous, well-characterized, bioactive, biotinylated peptides that have been developed over the past 25 years. Consequently, we explored the ability of conjugates fashioned from biotinylated analogs of gonadotropin-releasing hormone (GnRH) and avidinylated saporin to selectively target GnRH receptor-bearing pituitary cells. The biotinylated GnRH analogs all contained biotin moieties chemically linked to the epsilon amino group of [D-Lys6]GnRH; single and double spacer arms of aminohexanoic acid were included between the peptide and the biotin group. Some biotinylated GnRH analogs contained disulfide bonds between the peptide and biotin moieties. After conjugating the biotinylated peptides to avidinylated saporin, we tested the specific cytotoxic effect of the conjugates in cultures of dispersed rat pituitary cells.

Related Products: Avidinylated-SAP (Cat. #IT-09)

Cholera toxin B-saporin cytotoxicity is correlated with the extent of GM1 expression on the cell surface

Kohls MD, Lappi DA (2003) Cholera toxin B-saporin cytotoxicity is correlated with the extent of GM1 expression on the cell surface. Neuroscience 2003 Abstracts 325.16. Society for Neuroscience, New Orleans, LA.

Summary: Cholera toxin is composed of five B-subunits that mediate binding to the cell surface monosialoganglioside GM1, and one A-subunit that irreversibly activates adenylate cyclase. GM1 is found in high concentrations on astrocytes and the myelin of oligodendrocytes, as well as on many other cell types. A targeted toxin was developed consisting of the ribosome-inactivating protein saporin coupled to the B-subunit of cholera toxin (CTB) for the purpose of eliminating cells that express GM1. This targeted toxin (CTB-SAP) binds to cell-surface GM1 and the entire molecule is then internalized. Saporin separates from CTB and is released from the endosome to inactivate ribosomes. The cytoxicity of CTB-SAP in a cell-based in vitro assay can be inhibited by the addition of free CTB, indicating binding specificity. CTB-SAP has been tested on a variety of cell lines and the effectiveness of the targeted toxin correlates with the extent of GM1 cell surface expression as demonstrated by fluorescence-activated cell sorting (FACS) analysis. For example, using FACS analysis, RBL-2H3 cells exhibit an 88% shift when labeled with CTB-FITC. The ED50 of CTB-SAP in a cytoxicity assay on these cells is 380 fM, which corresponds to 9150 CTB-SAP molecules per cell. In comparison, HS294T cells produce a 48% shift in FACS, and the ED50 in the cytotoxicity assay is 5.5 pM. The correlation of surface GM1 number with ED50 indicates that the number of saporin molecules internalized is of primary importance in the process of cytotoxicity. CTB-SAP has been used to demyelinate the lumbar spinal cord (Jasmin et al.), eliminate sympathetic preganglionic neurons, and eliminate facial motoneurons in the rat (Llewellyn-Smith et al.). CTB-SAP is an effective and specific tool for the in vitro and in vivo elimination of cells that express GM1 on the cell surface.

Related Products: CTB-SAP (Cat. #IT-14)

Ablation of a population of NK-1 expressing neurons in the dorsal horn of the spinal cord does not induce αβ sprouting into lamina II

Woods M, Whiteside G, Pearson M, Pomonis J, Turchin P, Walker K (2003) Ablation of a population of NK-1 expressing neurons in the dorsal horn of the spinal cord does not induce αβ sprouting into lamina II. Neuroscience 2003 Abstracts 64.11. Society for Neuroscience, New Orleans, LA.

Summary: Peripheral nerve injury results in hyperalgesia and allodynia. It has been proposed that sprouting of myelinated touch responsive Aβ-fibers into the innervation territory of pain sensitive C fibers in the spinal cord contributes to these abnormal behaviors. In has further been postulated that excitatory cell death of spinal cord neurons may result in “vacant synapses” that induce sprouting (Woolf et al., 1992). We have investigated whether selectively ablating a population of cells in laminae I and II, using intrathecal (i.t.) SP-saporin (SP-SAP), will induce sprouting from deeper laminae. Male Sprague-Dawley rats were either injected i.t. at the lumbar region with SP-SAP (1 μl, 5 μM) or the sciatic nerve was axotomised at the mid-thigh level. Two weeks later the sciatic nerve was injected with the retrograde tracer, cholera toxin-β subunit (CTB) (2 μl, 2%) which selectively traces Aβ-fibers. Three days post CTB the animals were perfused, the lumbar ganglia and spinal cord harvested, sectioned and stained immunohistochemically for NK-1 and CTB. As previously described axotomy resulted in considerable CTB immunostaining in laminae I, II and III compared to non-axotomised controls in which it was present only in I and III. SP-SAP i.t. resulted in a substantial reduction of NK-1 like immunostaining in the spinal cord compared to saline injected controls. CTB was not detected in lamina II of spinal cords from animals with an ablation of NK-1 expressing cells. These results suggest that the death of dorsal horn neurons does not induce sprouting of Aβ-fibers into lamina II.

Related Products: SP-SAP (Cat. #IT-07)

Spinal neurons that possess the substance P receptor (SPR) modulate descending systems that control excitability of spinal nociceptive neurons

Khasabov SG, Ghilardi JR, Mantyh PW, Simone DA (2003) Spinal neurons that possess the substance P receptor (SPR) modulate descending systems that control excitability of spinal nociceptive neurons. Neuroscience 2003 Abstracts 13.3. Society for Neuroscience, New Orleans, LA.

Summary: We have recently shown that ablation of spinal SPR-expressing spinal neurons by intrathecal application of the cytotoxin conjugate substance P-saporin (SP-SAP) prevents the development of sensitization produced by intraplantar injection of capsaicin (Khasabov et al., 2002) and reduced hyperalgesia produced by inflammation and nerve injury (Mantyh et al., 1997; Nichols et al., 1999). Since the majority of spinal SPR-expressing neurons project to the brain, it is possible that these neurons are an integral part of ascendingdescending circuitry that modulates excitability of spinal nociceptive neurons. Here we studied the contribution of ascending SPR positive neurons in the regulation of brain stem descending pathways that pass through the dorsolateral funiculus (DLF) and modulate spinal cord excitability and sensitization. Rats were given an intrathecal injection of vehicle (0.9% NaCl, 10μl) or SP-SAP (5·10-6M, 10μl) at the lumbar enlargement 30 days prior to electrophysiological recording from lumbar spinal neurons. Spontaneous activity and evoked responses of nociceptive neurons to heat (35-51.°C) and mechanical stimuli (von Frey monofilaments) were obtained before and 1 hour after ipsilateral DLF transection. In vehicle-treated animals, DLF transection produced a 183% increase spontaneous activity, a leftward shift in the temperature-response curve, and a 60% increase in the number of impulses evoked by mechanical stimuli (n=25). In contrast, neurons in the SP-SAP group did not show any changes in spontaneous or evoked activity after DLF transaction (n=29). We conclude that ascending spinal SPR-possessing neurons modulate activity of descending inhibitory systems that pass through the DLF.

Related Products: SP-SAP (Cat. #IT-07)

Progressive effects of cholinergic depletion on cortical functional properties in the somatosensory cortex of rats

Herron P, Ismail NS (2003) Progressive effects of cholinergic depletion on cortical functional properties in the somatosensory cortex of rats. Neuroscience 2003 Abstracts 61.11. Society for Neuroscience, New Orleans, LA.

Summary: The amount and duration of cholinergic depletion of basal forebrain input appear to be important for how significant the functional capacity of cortical neurons and behavior are affected. Firstly, it is not known whether there is a correlative relationship between the level of cholinergic depletion and the level of degraded functional properties or whether there is a threshold of depletion, beyond which no further degradation occurs. Secondly, it is not known whether similar levels of cholinergic depletion over different periods cause the similar or different effects on functional capacities and behavior. These experiments were done in the posteromedial barrel subfield (PMBSF) cortex of young adult Sprague-Dawley rats. Selective lesion of cholinergic neurons in the NBM was achieved with cortical or intraventricular injections of the immunotoxin (IT), 192 IgG saporin. Electrophysiological recordings and whisker use in exploratory behavior were monitored for different post-injection survival periods. Results show that cholinergic depletion causes a significant decrease in the magnitude of evoked activity and an increase in the size of receptive fields for different periods. Observations of exploratory behavior showed that animals used whiskers controlled by cholinergic depleted cortex less than the whiskers controlled by non-cholinergic depleted cortex. Thus, cholinergic depletion leads to effects that significantly alter the functional capacity of the cortex and the behavioral use of those whiskers.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Purkinje cell depletion by ox7-saporin impairs eyeblink conditioned excitation and inhibition in rats.

Nolan BC, Freeman JH (2003) Purkinje cell depletion by ox7-saporin impairs eyeblink conditioned excitation and inhibition in rats. Neuroscience 2003 Abstracts 87.3. Society for Neuroscience, New Orleans, LA.

Summary: The role of the cerebellar cortex in conditioned excitation has been demonstrated by studies that used lesions, inactivation, and electrical stimulation (e.g., Attwell, Rahman, & Yeo, 2001, J Neurosci, 21, 5715-5722). However, very little evidence exists concerning the role of the cerebellar cortex in conditioned inhibition. Moreover, there are multiple blink control zones in the cerebellar cortex (Hesslow, 1994, J Physiol, 476, 229-244), which complicates the interpretation of studies that use localized lesions. In the current study, rats were infused with the immunotoxin OX7-saporin into the lateral ventricles to selectively destroy Purkinje cells throughout the cerebellar cortex (Angner, et.al, 2000, Neurotox, 21, 395-404). The OX7- saporin method provides advantages relative to other methods, including the ability to deplete Purkinje cells after initial training. In Experiment 1, rats were given saline or OX7-saporin prior to excitatory conditioning training, which was established using a tone conditioned stimulus (CS) paired with a periorbital shock unconditioned stimulus (US). Rats given OX7-saporin had nearly complete Purkinje cell loss and acquisition of excitatory conditioning was severely impaired. In Experiment 2, rats were first trained with excitatory conditioning procedures, followed by infusion of either saline or OX7-saporin. After a two-week post-infusion period, the rats were given reacquisition training. After reacquiring excitatory conditioning, the rats were trained using a feature-negative discrimination procedure consisting of trials with CS-US pairings and trials with a non-reinforced tone-light compound stimulus. Rats treated with OX7-saporin showed a significant impairment in reacquisition and acquisition of conditioned inhibition. The results suggest that Purkinje cells are critically involved in the acquisition of both conditioned excitation and inhibition in rats.

Related Products: OX7-SAP (Cat. #IT-02)