sfn2005

Rinaman L, Maldovan V (2005) Experimental dissociation of neural circuits underlying anorexic and conditioned avoidance responses to LiCl in rats. Neuroscience 2005 Abstracts 529.7. Society for Neuroscience, Washington, DC.

Summary: The central nucleus of the amygdala (CeA) receives viscerosensory input from noradrenergic (NA) neurons in the nucleus of the solitary tract (NST) and from peptidergic non-NA neurons in the lateral parabrachial nucleus (laPBN). A previous study (J. Neurosci. 23:10084-92) demonstrated that NA neurons in the caudal NST are necessary for cholecystokinin (CCK) to inhibit food intake in rats, but are unnecessary for CCK to activate Fos expression in the laPBN and CeA. The laPBN and CeA are integral components of central neural circuits that underlie the formation and expression of conditioned flavor avoidance (CFA). Thus, the neural substrates for treatment-induced anorexia may be separable from those for CFA. To test this idea, saporin toxin conjugated to an antibody against dopamine β hydroxylase was microinjected bilaterally into the caudal NST in adult male rats in order to selectively lesion NA neurons. Three weeks later, lesioned and sham control rats were tested for the ability of 0.15M LiCl (2% BW, i.p.) to inhibit food intake and to support conditioned flavor avoidance (CFA). Anorexia after LiCl was significantly blunted in lesioned rats compared to sham controls, similar to our previous findings in lesioned rats after CCK treatment. However, LiCl still supported robust CFA in lesioned rats, and its magnitude was similar to that seen in sham controls. A terminal Fos study revealed intact LiCl-induced activation of neural Fos expression in the laPBN and CeA in lesioned rats, despite significant loss of NA neurons in the caudal NST. These new findings support the view that NA neurons in the caudal NST are unnecessary for laPBN and CeA neural responses to viscerosensory stimulation, and also are unnecessary for the learning and expression of conditioned flavor avoidance.

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Mattsson A, Schilstrum B, Svensson TH, Olson L (2005) Cortical cholinergic deficiency enhances amphetamine-induced dopamine release in accumbens. Neuroscience 2005 Abstracts 557.8. Society for Neuroscience, Washington, DC.

Summary: Disturbances in cholinergic functions have been implicated in schizophrenia. We have recently shown that cholinergic denervation of neocortex produced by local injection of the immunotoxin 192 IgG-saporin into nucleus basalis magnocellularis (nbm) leads to an increased sensitivity to d-amphetamine in adult female rats. The objective of the current study was to investigate if this effect was paralleled by an increased amphetamine-induced release of dopamine in accumbens. The corticopetal cholinergic projections were lesioned by intraparenchymal infusion of 192 IgG-saporin into nbm in adult rats. D-amphetamine-induced dopamine release in nucleus accumbens was measured by in vivo microdialysis two to three weeks after lesioning. We find that amphetamine causes a greater release of dopamine in rats with cortical cholinergic denervation than in sham lesioned controls. The duration of the amphetamine-effect was also significantly longer in the 192 IgG-saporin lesioned group compared to controls. The results suggest that abnormal responsiveness of mesencephalic dopaminergic neurons could be secondary to cortical cholinergic deficiency. This in turn might constitute one possible contributing pathophysiological factor in schizophrenia.

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Pedersen AF, Kostova V, Christensen E, Veng LM, Lohals R, Knudsen GM, Aznar S (2005) Intraventricular IgG192-saporin lesions lead to altered 5-HT2A receptor levels in the hippocampus. Neuroscience 2005 Abstracts 559.17. Society for Neuroscience, Washington, DC.

Summary: Background: Alzheimer’s disease (AD) is the most frequent neurodegenerative disorder in humans. One of the traits of the disease is the presence in the brain of beta-Amyloid plaques and loss of cholinergic neurons in the basal forebrain. Other transmittersystems especially serotonin may be involved in the patophysiology of AD. Clinical studies have observed a higher incidence of depression among AD patients and a higher risk of developing dementia when diagnosed with major depression. It is known that serotonin and serotonin receptors, among them 5-HT2A receptors (5-HT2AR), are involved in depression. Interestingly, recent PET-studies have shown lower 5-HT2AR levels in entorhinal cortex and hippocampus in early stages of AD. Objectives: Our aim was to investigate whether 5-HT2AR levels were affected in the hippocampus after lesioning the cholinergic neurons in the basal forebrain, thereby highlighting a possible interaction between the serotonergic and the cholinergic transmitter systems. Methods: Intraventricular injection of 5ug IgG192-Saporin or saline in adult Wistar male rats. After 20 weeks the rats were sacrificed and the hippocampus were isolated. After homogenisation the levels of 5-HT2AR were determined by western blot. Results: Downregulation of the 5-HT2AR levels were observed after 20 weeks. 5-HT2AR levels for animals receiving IgG192-Saporin for 1, 2 and 4 weeks will also be investigated. Conclusion: Our results show a direct effect of cholinergic lesions on hippocampal 5-HT2AR. This may be explained by a compensatory effect of the serotonergic system for the loss of cholinergic input as there may be a balance between these two systems in the hippocampus.

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Kabogo DN, Kar S (2005) Sortilin and p75NTR: localization in adult rat brain and their alterations following pharmacological manipulations. Neuroscience 2005 Abstracts 148.14. Society for Neuroscience, Washington, DC.

Summary: Neurotensin receptor-3 is a single trans-membrane domain 100 kDa protein whose structure is identical to the human gp95/sortilin. This receptor is involved in intracellular trafficking of sphingolipid activator proteins, and may have a role in sorting other soluble lysosomal proteins. Recently, it has been shown that sortilin, under in vitro paradigm, acts as a co-receptor and molecular switch governing the low-affinity neurotrophin receptor p75NTR mediated cell death induced by pro-nerve growth factor. However, very little is currently known about the cellular distribution of sortilin and its possible localization in neurons expressing p75NTR and/or cholinergic markers in the adult rat brain. Using western blotting and immunohistochemistry, we report that immunoreactive sortilin is ubiquitously expressed in the adult rat brain, including the cortex, striatum, basal forebrain, hippocampus, brainstem and cerebellum. In the normal brain immunoreactive sortilin is not found to be present in the basal forebrain cholinergic neurons expressing p75NTR but localized in the cholinergic interneurons of the striatum and motoneurons of the brainstem. Additionally, neither the level nor the expression of sortilin is altered following immunotoxin 192-IgG saporin-induced death of the basal forebrain cholinergic neurons. However, systemic administration of kainic acid, a potent neurotoxin, was found to induce the expression of p75NTR in the subset of sortilin-containing striatal cholinergic neurons which are believed to undergo apoptosis. These results, taken together, suggest that sortilin in normal brain is not expressed in p75NTR containing neurons and may differentially influence p75NTR–mediated cell death in the brain.

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Kanju PM, Sims CM, Parameshwaran K, Huggins K, Josephson EM, Suppiramaniam V (2005) Medial-septal cholinergic denervation leads to synaptic glutamatergic dysfunction in hippocampus. Neuroscience 2005 Abstracts 157.2. Society for Neuroscience, Washington, DC.

Summary: Accumulating evidences support the role of septohippocampal cholinergic projections in learning and memory mechanisms. Hence, a complete and selective destruction of the septal cholinergic neurons projecting to the hippocampus by immunotoxin 192 IgG-saporin results in memory impairment. Alterations in glutamate receptor (NMDA & AMPA receptors) binding properties have also been reported following septohippocampal cholinergic denervation. A decrease in NMDA binding and an increase or no change in AMPA binding was observed seven days after lesioning. Therefore, it is important to study the effects of cholinergic lesioning on functional properties of glutamate receptors. This study investigated the electrophysiological properties of AMPA and NMDA receptors 4 to 6 days after medial septal lesioning. Selective medial-septal lesioning was performed in rats with the immunotoxin 192-IgG saporin. Whole cell recording of mEPSC and sEPSC were performed in CA1 hippocampal region in slices from lesioned and sham lesioned animals. The single channel recordings of synaptosomes isolated from hippocampi of these animal groups incorporated into lipid bilayer were also performed. Our results indicate a reduction in the frequency and amplitude of AMPA and NMDA mediated mEPSCs and sEPSCs of animals lesioned with 192-IgG saporin. Furthermore, single channel recording of isolated synaptosomes demonstrate a reduction in channel open probability (30-50% for AMPA & 20-32% for NMDA receptors), and conductance (35-46% AMPA & 28-39% for NMDA receptors). Collectively, our results indicate that synaptic AMPA and NMDA receptor functions are altered 4-6 days following medial septal lesioning.

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Bailey AL, Bennett G, Ribeiro-da-Silva A (2005) Selective ablation of non-peptidergic C-fibers using IB4-saporin as a tool to identify the functional role of these fibers in pain transmission. Neuroscience 2005 Abstracts 169.14. Society for Neuroscience, Washington, DC.

Summary: Non-peptidergic primary sensory afferents represent a sub-population of unmyelinated C-fibres implicated in the transmission of pain-related information. Evidence indicates that these afferents play a role in pain transmission distinct from peptidergic afferents. However, their exact function in pain signalling is unknown. Investigating alterations in pain behaviours and changes in neurotransmitter and receptor expression in the absence of these sensory afferents may provide some insight into their relative importance in acute and chronic pain conditions. We therefore examined the functional consequences of the selective ablation of non-peptidergic fibres in numerous models of acute pain using Isolectin B4 conjugated to saporin (IB4-SAP). Unilateral injection of IB4-SAP into the sciatic nerve resulted in the selective ablation of IB4-positive neurons in the ipsilateral dorsal root ganglion (DRG). Examination of the central terminals of non-peptidergic primary afferents in the dorsal horn revealed the near complete loss of IB4-positive, P2X3 immunoreactive (IR) varicosities. Moreover, there were marked decreases in TRPV1-IR and substance P (SP-IR) with no change in calcitonin-gene-related peptide (CGRP). Examination of a marker of inhibitory interneurons revealed no changes in GAD-IR. Behavioural analysis showed that IB4-SAP treatment had no effect on acute thermal sensitivity, acute mechanical or cold sensitivity. In an animal model of acute inflammation, IB4-SAP treatment had no effect on inflammatory heat hyperalgesia or mechanical allodynia. However, animals treated with IB4-SAP showed attenuated heat hyperalgesia induced by capsaicin 30 and 60 minutes post-injection. Data relative to acute nociceptive thresholds after other chemical stimuli will be presented. These data indicate that non-peptidergic fibres are minimally involved in acute and inflammatory pain, and may play a more prominent role in high threshold thermal sensation.

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Li X, Bynum T, Hayashida K, Eisenach JC (2005) Role of IB4-containing afferents in the effect of IT clonidine. Neuroscience 2005 Abstracts 171.22. Society for Neuroscience, Washington, DC.

Summary: Alpha2 adrenoceptors diminish pain transmission in animals with normal condition. Our previous data demonstrated clonidine, an Alpha2 adrenoceptor agonist, inhibited calcium influx after an electrical stimulation in the acutely cultured DRG cells from normal animal, 80% of which are Isolectin B4 (IB4) positive. Therefore we assume intrathecal clonidine produces antinociception primarily by actions on IB4-expressing afferents, and clonidine effect will be decreased with the loss of IB4 containing afferents. In the current report, normal rats received an intra-nerve injection of 2 μg of saporin conjugated IB4 (Sap-IB4), a targeted cytotoxin to IB4-expressing neurons, or a 6 μg of saporin as the control in the rat sciatic nerve. Effects of 30 μg intrathecal clonidine were observed for antinociception to thermal and mechanical stimuli in both ipsi- and contra- lateral side to the injection weekly, before and after Sap-IB4 injection for three weeks. Immunocitochemistry study demonstrated that three weeks of Sap-IB4 treatment dramatically decreased IB4 expression in DRG cells or spinal afferent fibers in the ipslateral side. The basal thermal withdrawal latency and mechanical withdrawal threshold were slightly increased by Sap-IB4 in the ipsilateral side one week after injection, which were returned to normal three weeks later. Additionally, the effeccy of 30 μg clonidine for antinociception to thermal and mechanical stimuli was significantly decreased at the end of treatment. These observations suggested IB4 containing afferents may play a very important role in intrathecal clonidine mediated antinociception.

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Buse JE, Kim I, Wilson RE, Wellman CL (2005) Contributions of NMDA receptors to cortical plasticity after cholinergic deafferentation. Neuroscience 2005 Abstracts 214.21. Society for Neuroscience, Washington, DC.

Summary: Plasticity of frontal cortex is altered in aging rats: lesions of the nucleus basalis magnocellularis (NBM) increase both expression of the AMPA receptor subunit GluR1 and dendritic spines in frontal cortex of young adult but not aging rats. Others have shown that NMDA receptors are reduced in aged cortex. Given the role of NMDA receptors in synaptic plasticity, altered transmission at NMDA receptors may be responsible for the differential cortical plasticity in aging rats. To begin to test this hypothesis, we assessed the effect of NMDA receptor blockade on GluR1 subunit expression and dendritic spine density on pyramidal cells in layer II-III of frontal cortex after either sham or 192 IgG saporin lesions of the NBM. Young adult rats received unilateral sham or 192 IgG saporin lesions of the NBM, along with subscapular implants of osmotic minipumps delivering either MK801 (6 mg/ml; 0.5 μl/h) or phosphate-buffered saline. Two weeks after surgery, rats were euthanized and brains were processed for either immunohistochemical labeling of GluR1 subunit protein or Golgi-Cox histology. To quantify GluR1 expression, an unbiased stereological technique was used to estimate the number of intensely labeled neurons. To quantify spine density, second- and third-order basilar dendrites of Golgi-stained pyramidal cells were drawn and spines were counted. NBM lesions significantly increased both GluR1 expression and spine density, by 83% and 28% respectively. While NMDA blockade alone had no effect, it prevented the lesion-induced increases in GluR1 expression and spine density. Thus, transmission at NMDA receptors may be necessary for synaptic plasticity after cholinergic deafferentation, and age-related changes in NMDA receptors may contribute to altered plasticity of frontal cortex of aging rats.

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Furlong TM, Carrive P (2005) Hypocretin/orexin neurons and the perifornical hypothalamus play a more important role in contextual fear than in restraint stress. Neuroscience 2005 Abstracts 304.11. Society for Neuroscience, Washington, DC.

Summary: We investigated the role of the neuropeptide hypocretin (Hcrt; also known as orexin) in two different types of stress: conditioned fear to context and restraint stress. For contextual fear, male Wistar rats were tested by re-exposure to a chamber where electric footshocks had previously been administered. For restraint stress, the rats were restrained in tight Plexiglas tubes. In the first study, lesions of the perifornical region of the hypothalamus (PeF; where Hcrt neurons are located) were made with a Hcrt-saporin toxin prior to testing. The cardiovascular response was measured using radio-telemetry. The pressor and tachycardic responses to the context were reduced by 77% and 74% respectively, compared to an intact group (p<0.001, for both comparisons). The lesioned group also displayed significant reductions in freezing (by 67%) and ultrasonic vocalisations (by 74%). In contrast, the cardiovascular response to restraint stress did not differ between the two groups (p>0.5). In the second study, two hours after the tests, the rats were euthanased (200 mg/kg sodium pentobarbitone, i.p) and their brains removed and processed for double immunohistochemical detection of Hcrt and Fos. There was a higher percentage of Hcrt neurons double labeled with Fos after contextual fear (17%) than after restraint stress (6%), which indicates that more Hcrt neurons were active during contextual fear (p=0.024). These studies suggest that the PeF region and Hcrt neurons play a more important role in contextual fear than in restraint stress.

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Kalinchuk AV, Stenberg D, Rosenberg PA, Porkka-Heiskanen T (2005) On the role of the basal forebrain cholinergic neurons in regulation of recovery sleep. Neuroscience 2005 Abstracts 308.8. Society for Neuroscience, Washington, DC.

Summary: Basal forebrain (BF) is an critical site in regulation of propensity for sleep (Porkka-Heiskanen et al., 2000; Kalinchuk et al., 2003).We have recently shown that development of recovery sleep after sleep deprivation (SD) might be mediated by release of nitric oxide (NO) in the BF during SD (Kalinchuk et al., 2003; 2004). To further elucidate the role of BF neuronal mechanisms in regulation of NO-mediated recovery sleep we selectively destroyed BF cholinergic neurons and compared effects of SD and pharmacologically increased NO level (induced by NO donor infusion) to the effects observed in intact animals. Male rats were implanted with electrodes for EEG/EMG recording and guide cannulae for microdialysis probes targeting the BF. The experimental schedule for each rat included: recording of natural sleep-waking cycle; SD for 3h; infusion of NO donor (DETA NONOate) for 3h. In separate group of rats immunotoxin 192 IgG-saporin was injected into the BF and the same experimental schedule was performed. After the end of experiments brains were taken for validation of the quality of cholinergic cells lesion and/or probes locations. In all intact rats SD induced significant increase in subsequent NREM sleep by 30.2±3%. Infusion of DETA NONOate into the BF increased sleep by 35.2±4%. Relative delta power was increased by 44.4±8% and 44.1±19%, respectively. After lesion of the BF cholinergic cells recovery NREM sleep after SD was significantly attenuated (9.5±3% increase as compared with baseline). Effect of DETA NONOate infusion was also inhibited (3.1±4% decrease as compared with baseline). Increases in relative delta power were totally abolished. Our data allow to conclude that cholinergic neurons in the BF play an important role in regulation of SD-induced recovery sleep which is mediated by release of NO.

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