sfn2003

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)

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)

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)

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.

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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)

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)

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.

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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)

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.

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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.

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