References

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)

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.

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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.

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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)

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.

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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.

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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.

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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.

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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.

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