Abstracts from Society for Neuroscience (SFN) Washington, D.C. • November 12-16, 2005

33 entries found for : sfn2005

Cholinergic lesions produce selective effects on cognitive performance in rats

Gibbs RB, Fitz NF, Johnson DA (2005) Cholinergic lesions produce selective effects on cognitive performance in rats. Neuroscience 2005 Abstracts 881.1. Society for Neuroscience, Washington, DC.

Summary: Cholinergic projections from the basal forebrain play an important role in cognitive processes; however, the degree to which damage to specific projections contributes to impairment within specific cognitive domains is unclear. In the present study, cholinergic projections to the hippocampus and/or frontal cortex of young adult, ovariectomized Sprague-Dawley rats were selectively destroyed by injecting 192 IgG-saporin (SAP) into the medial septum (MS), the nucleus basalis magnocellularis (NBM), or both the MS and NBM (MSNBM). Controls received injections of sterile saline. Animals were then tested for learning and memory impairments using a series of tasks, including a delayed matching-to-position (DMP) T-maze task, an operant configural association (CA) negative patterning task, and a 12-arm radial maze (RAM) task, administered in that order. Results reveal different effects of the lesions on the different tasks. For example, SAP lesions of the MS, as well as combined lesions of MS and NBM significantly impaired acquisition the DMP task; however, once animals had reached criterion, cholinergic lesions did not alter decrements in performance produced by increasing the intertrial delay. In contrast, SAP lesions of the MS had no significant effect on acquisition of the CA task, although combined lesions of MS and NBM produced a trend toward impairment on the CA task among animals with the most severe cholinergic depletion. Likewise, combined lesions significantly impaired acquisition of the RAM task. In general, combined lesions produced greater impairments than lesions of either the MS or NBM alone. Significant correlations between acquisition of the DMP and RAM tasks and ChAT activity in the hippocampus, frontal cortex, and occipital cortex, were also detected. These data demonstrate that removal of cholinergic projections to the hippocampus and frontal cortex produce cognitive impairments that are lesion specific as well as task dependent.

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192 IgG-saporin lesions to the nucleus basalis magnocellularis (NBM) do not disrupt the retention of learning set formation

Bailey AM, St Germain J, Tyler MM (2005) 192 IgG-saporin lesions to the nucleus basalis magnocellularis (NBM) do not disrupt the retention of learning set formation. Neuroscience 2005 Abstracts 881.2. Society for Neuroscience, Washington, DC.

Summary: Male Long Evans rats (Rattus norvegicus) were used to investigate the role of the nucleus basalis magnocellularis (nBM) in the retention of a previously acquired learning set rule. All rats had successfully acquired an olfactory discrimination learning set by demonstrating above chance performance on trial 2 across 42 olfactory discrimination problems. Following the initial acquisition of learning set, animals were given bilateral 192 IgG-saporin (0.375 µg/µl; 0.4 µl per hemisphere) lesions to the nBM. Assessment of open field activity indicated that there were no group differences in general activity levels or emotionality before or after surgery. Retention of learning set was tested 10 days following surgery with 20 novel, odor-unique olfactory discrimination learning set problems. Control and nBM lesioned animals performed significantly higher than expected by chance on trial 2 of the novel problems suggesting retention of a learning set hypothesis. However, rats with 192 IgG-saporin nBM lesions performed learning set at a significantly lower level than control animals as measured by trial 2 percentage correct. Results suggest that damage to the nBM disrupts general performance on a cognitively demanding task, but does not block retention of the learning set rule.

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Facilitation of conditioned odor aversion by entorhinal cortex lesion in the rat is reversed by cholinergic lesion in the basal forebrain

Ferry B, Herbeaux K, Petoukhova-Traissard N, Galani R, Cassel J, Majchrzak M (2005) Facilitation of conditioned odor aversion by entorhinal cortex lesion in the rat is reversed by cholinergic lesion in the basal forebrain. Neuroscience 2005 Abstracts 881.6. Society for Neuroscience, Washington, DC.

Summary: In the rat, conditioned odor aversion (COA) corresponds to the avoidance of an odorized-tasteless solution (conditioned stimulus, CS) previously associated with toxicosis (unconditioned stimulus, US). Evidence suggests that the entorhinal cortex (EC) is part of the neural substrate involved in the acquisition of COA. Indeed, we showed that EC lesion facilitated CS-US association and rendered it resistant to lengthening of the interstimulus interval (ISI). This facilitation phenomenon might correspond to a lengthening of the olfactory CS memory trace, rendering the association with the subsequent US possible. Because i) all our EC-lesioned rats showed septo-hippocampal cholinergic sprouting, and ii) scopolamine infusions into the dentate gyrus reversed performance in EC-lesioned but not in sham-operated rats in a spontaneous olfactory preference test, we suggested that COA facilitation resulted from enhanced cholinergic activity in the hippocampus. In order to test this hypothesis, we studied the effect of a cholinergic basal forebrain lesion combined to an EC-lesion during COA. Male Long-Evans rats subjected to bilateral EC lesions and intraventricular infusions of the selective toxin 192 IgG-saporin received odor-US pairings with a short or long ISI. Results showed that sham-lesioned rats displayed COA with the short, but not the long ISI, whereas EC-lesioned rats showed COA with both ISI. More interestingly, rats with double lesions did not differ from controls, suggesting that the cholinergic lesion suppressed the effect of EC-lesions. These results strongly suggest that the facilitative effects observed in EC-lesioned animals during COA are due, at least in part, to the septo-hippocampal cholinergic sprouting elicited by the EC lesion. Moreover, they suggest that the hippocampal cholinergic system is involved in the control of memory processes underlying the association between the olfactory CS and the US during acquisition of COA.

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Time-dependent neurotrophins effect on cholinergic denervation and hippocampal sympathetic ingrowth following 192 IgG-saporin lesioning of medial septum

Kolasa K, Parsons D, Harrell LE (2005) Time-dependent neurotrophins effect on cholinergic denervation and hippocampal sympathetic ingrowth following 192 IgG-saporin lesioning of medial septum. Neuroscience 2005 Abstracts 1004.4. Society for Neuroscience, Washington, DC.

Summary: In rat,injection of specific cholinotoxin,192 IgG-saporin into the medial septum results not only in a selective denervation of hippocampus(CD),but in an ingrowth of peripheral sympathetic fibers,originating from the superior cervical ganglion,into the hippocampus.This process has been termed hippocampal sympathetic ingrowth(HSI).A similar process,in which sympathetic noradrenergic axons invade hippocampus,may also occur in Alzheimer's disease(AD). The severity of cognitive decline in AD patients has been linked to multiple factors including cholinergic and neurotrophic factors and their receptors,which undergo selective alterations throughout the progression of AD.It is known that the sites of synthesis of NGF(nerve growth factor),BDNF(brain derived-neurotrophic factor)and LIF (leukemia inhibitory factor)in rat septo-hippocampal system are predominantly hippocampal neurons.By using 192 IgG-saporin we have been able to mimic some of the cardinal features of AD e.x.cholinergic denervation and hippocampal sympathetic ingrowth and to study their effect on neurotrophins in dorsal hippocampus.Thus,2,8,and 12 weeks after injection of 192 IgG-saporin we measured NGF, BDNF and LIF protein and mRNA expression using Western blot and RT-PCR techniques, respectively.Choline acetyltransferase activity(ChAT) and norepinephrine(NE) concentration was also detected. Significant alterations were found in NGF and LIF protein expression(decrease at 8 weeks and increase at 12 weeks post lesions)in HSI group. Significant decrease of BDNF(mature form) protein expression was found in CD group over whole period of time. There was significant decrease found in BDNF mRNA expression in CD,with normalization in HSI group 12 weeks post lesions. Results of the study suggest that neurotrophins are affected by cholinergic denervation and may play an important role in regulation and development of HSI,which might be a beneficial phenomenon for restoration at least some of cognitive function.

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Immunolesions of glucoresponsive projections to the arcuate nucleus alter glucoprivic feeding and luteinizing hormone secretion but not sex behavior in adult male rats

Fraley GS (2005) Immunolesions of glucoresponsive projections to the arcuate nucleus alter glucoprivic feeding and luteinizing hormone secretion but not sex behavior in adult male rats. Neuroscience 2005 Abstracts 758.7. Society for Neuroscience, Washington, DC.

Summary: Metabolic signals such as insulin, leptin and glucose are known to alter hypothalamic function. Although insulin and leptin are known to directly alter hypothalamic areas that regulate reproduction, the mechanisms by which glucose alters reproductive function are not as clear. Catecholaminergic neurons in the A1/C1 region of the hindbrain are glucose-responsive and project to the arcuate nucleus. To determine if this pathway is involved in the regulation of sex behavior and luteinizing hormone (LH) secretion, this catecholamingergic pathway was lesioned by injecting saporin conjugated to anti-dopamine-β-hydroxalase (DSAP) or unconjugated saporin (SAP) into the arcuate nucleus of adult male rats. Rats were given glucoprivic challenges then feeding and sex behaviors were observed. As was expected, the DSAP treated rats showed a significant decreased in feeding during glucoprivation (250 mg/kg 2-deoxy-D-glucose, 2DG) compared to SAP controls (p < 0.05). Glucoprivation caused a significant reduction in sex behavior (p < 0.05) in both SAP and DSAP animals equally, compared to saline treatments in either treatment group. At the end of the experiment, animals were given a final challenge with 2DG or saline, killed by decapitation and trunk blood was assayed for plasma LH levels. In SAP animals, 2DG elicited a significant decrease in plasma LH levels (p < 0.05). However, in DSAP animals there was a significant increase (p < 0.05) in plasma LH levels compared to saline-treated rats. These data indicate that the A1/C1 efferents to the ventromedial hypothalamus are involved in the glucostatic regulation of feeding behavior and LH secretion, but not sex behavior in the adult male rat.

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Immunolesion of p75 NGF receptor in the mouse SCN attenuated light-induced phase shift of the circadian wheel-running rhythm

Vijayakumar S, Masood A, Smith M, Clark JP, Nelson DE, Ding JM (2005) Immunolesion of p75 NGF receptor in the mouse SCN attenuated light-induced phase shift of the circadian wheel-running rhythm. Neuroscience 2005 Abstracts 766.18. Society for Neuroscience, Washington, DC.

Summary: Mammalian circadian rhythms are regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus. Alhough the SCN can orchestrate these rhythms in the absence of external cues, it is entrained to environmental cycles through the retinohypothalamic tract. Light-induced phase shifts in circadian rhythm is a classic example of short-term environmental stimuli inducing lasting changes in intracellular signals and gene expression within the SCN cells that alter the phase of the SCN pacemaker and allow entraiment. Since neurotrophins are known to mediate neural plasticity, we investigated the role of brain-derived neurotrophic factor (BDNF) on resetting the phase of the SCN both in vitro and in vivo. We used the SCN brain slice model to study the direct effect of BDNF on the circadian rhythm. Briefly, coronal hypothalamic slices containing the SCN were prepared using 129B/6 mice. The circadian rhythm of the SCN neurons in the brain slice was monitored for 2-3 days by continuously sampling the spike frequencies with single-unit extracellular electrodes. Brief microdrop applications of BDNF (10 uM) induced robust phase delays at CT 16 and phase advances at CT 22. BDNF binds to neurotrophin receptors, including the low affinity p75NTR, which is localized in the SCN. When the toxin Saporin is conjugated to the antibody against p75NTR, it selectively destroys the cells expressing the p75NTR. Three weeks after the stereotaxic injection of the mu p75-Saporin (Advanced Targeting System) into the third ventricle (1 ul over 20 min), the p75NTR immunoreactivity in the mouse SCN is abolished. Immunolesion of the p75NTR in the SCN attenuated light-induced phase delays of the wheel running rhythm at CT16. Consistent with previous findings, our results support a role for BDNF and its receptor p75NTR, in resetting the circadian rhythm of the SCN in mice.

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Increased formalin behavior after selective destruction of μ opiate receptor-expressing dorsal horn neurons: impaired descending analgesic control?

Datta S, Kline IV RH, Wiley RG (2005) Increased formalin behavior after selective destruction of μ opiate receptor-expressing dorsal horn neurons: impaired descending analgesic control?. Neuroscience 2005 Abstracts 623.15. Society for Neuroscience, Washington, DC.

Summary: Spinal intrathecal injection of dermorphin-saporin (derm-sap) selectively destroys dorsal horn neurons expressing the mu-opiate receptor (MOR). In the present study, we sought to determine the effect of derm-sap (500 ng, i.t.) on responses to intraplantar formalin injection (25 ul of 5%). After formalin injection, rats were immediately placed into a clear observation chamber with a video camera beneath the floor. Rats were videotaped for 90 minutes and their behavior scored offline for one minute out of every 5 minutes. 120 minutes after formalin injection rats were anesthetized with pentobarbital and perfused with formalin. Spinal cord sections were stained for MOR and cholecystokinin (CCK) using standard immunoperoxidase techniques on adjacent 40 um sections from L4 spinal segment. Coded sections were used to assess MOR staining intensity by quantitative densitometry. Derm-sap treated rats showed no separation between phase I and II and spent more time than vehicle controls licking/guarding/biting the injected hindpaw during both phase I and II. Derm-sap significantly decreased dorsal horn MOR. Staining for CCK showed time dependant changes after derm-sap which was not present in PBS controls. These same derm-sap treated rats performed normally on hotplate at 44, 47 and 52 C and had normal analgesic responses to systemic morphine on 44, 47 and 52 C hotplates. We interpret these data to indicate that loss of the dorsal horn MOR-expressing neurons reduces the effect of descending analgesic mechanisms. Supported by NIH R21-DA14380 and Department of Veterans Affairs.

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Neurotoxic lesions of serotonin cells in the dorsal raphe reduce compulsive-like nest building in mice

Greene DM, Castillo MR, Alexander KA, McMahan A, Raap DK, Bult-Ito A (2005) Neurotoxic lesions of serotonin cells in the dorsal raphe reduce compulsive-like nest building in mice. Neuroscience 2005 Abstracts 796.10. Society for Neuroscience, Washington, DC.

Summary: Bi-directional selection for thermoregulatory nest-building behavior in house mice (Mus musculus) has resulted in a 40-fold difference in the amount of cotton used for nest-building between the high and the low selected lines (big and small nest-builders, respectively). The efficacy of serotonin re-uptake inhibitors (SSRIs), especially fluoxetine, for the treatment of obsessive-compulsive disorder (OCD) indicates a serotonergic involvement in the disorder. The repetitive nest-building behavior, characteristic of the big nest-builders, is a compulsive-like behavior that is responsive to SSRI treatment. We investigated the functional involvement of serotonergic pathways in excessive, repetitive nest-building behavior in mice by lesioning serotonergic cells in the dorsal raphe using the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) or SERT-saporin (Advanced Targeting Systems). 5,7-DHT lesioned mice had a significant decrease in the number of serotonin-stained cells in the dorsal raphe. No decrease was noted in serotonin staining after lesions performed with the SERT-saporin neurotoxin. Mice with successful 5,7-DHT lesions also significantly decreased compulsive-like nest-building as compared to sham and non-surgery controls. These data taken together with additional findings in these mice support the involvement of serotonin pathways in OCD. This data further supports the big nest-builders as a potentially valuable animal model of compulsive behaviors in humans and a means to more clearly identify neurobiological pathways involved in OCD.

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Facilitatory influences from the rostral ventromedial medulla (RVM) are required for pancreatic nociception

Vera-Portocarrero LP, Xie Y, King T, Lai J, Porreca F (2005) Facilitatory influences from the rostral ventromedial medulla (RVM) are required for pancreatic nociception. Neuroscience 2005 Abstracts 623.18. Society for Neuroscience, Washington, DC.

Summary: Pain is a frequent complaint of patients with pancreatitis or pancreatic cancer. An animal model of pancreatitis induced by dibutyltin dichloride (DBTC) is characterized by abdominal hypersensitivity to mechanical stimuli that appears by day 3 after induction of pancreatitis and persists for at least 10 days. We have used this model to evaluate the role of descending pain modulatory pathways from the RVM in the processing of visceral pain. Pancreatitis was induced in rats by a single tail vein injection of DBTC. Animals were monitored for mechanical sensitivity of the abdominal area as an index of pancreatic nociception using von Frey hairs applied to the surface of the abdomen and recording the frequency of withdrawals from stimulation. Six days after DBTC injection, when mechanical hypersensitivity was fully developed, lidocaine, or saline, was microinjected into the RVM. Lidocaine, but not saline, given into the RVM produced a time-related reversal of mechanical hypersensitivity which peaked by 20 min after injection in animals with pancreatitis. RVM lidocaine had no effect on rats without pancreatitis. A second group of rats received a single microinjection of the cytotoxin dermorphin-saporin into the RVM in order to ablate mu opioid receptor expressing cells that have been proposed to drive descending pain facilitation. 28 days later, the rats received DBTC and their response to mechanical stimulation was monitored daily. These rats showed mechanical hypersensitivity on day 3 after DBTC, but the sensory threshold reverted to normal level by day 6, while rats that had been pretreated with dermorphin, saporin, or water exhibited persistent mechanical hypersensitivity after DBTC out to day 10. These data suggest that a blockade of the descending input from the RVM by lidocaine is sufficient to block the pancreatitis-induced visceral pain, and that the mu opioid receptor expressing cells in the RVM are critical for the persistent pain state.

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Neurokinin 1 receptor containing interneurons of the BLA are putative candidates for the inhibitory component of feed-forward inhibition from the mPFC to the BLA

Truitt WA, Oberlin BG, Dietrich AD, Fitz SD, Shekhar A (2005) Neurokinin 1 receptor containing interneurons of the BLA are putative candidates for the inhibitory component of feed-forward inhibition from the mPFC to the BLA. Neuroscience 2005 Abstracts 796.12. Society for Neuroscience, Washington, DC.

Summary: The amygdala and in particular the basolateral nucleus of the amygdala (BLA) is a central site for fear and anxiety. The BLA is under tonic inhibition by a network of inhibitory interneurons. Additionally, cortical inputs can both excite or inhibit the output of the BLA, resulting in increases or decreases in anxiety/fear-like behaviors. In particular mPFC inputs to the BLA can suppress BLA output and inhibit fear conditioning. However, the mechanism by which this occurs is not fully understood. Evidence from electrophysiological studies suggests a feed forward inhibitory relationship between the mPFC and the BLA. This feed forward inhibition putatively occurs by mPFC-glutamatergic inputs exciting GABAergic interneurons of the BLA, which in turn suppress firing of the BLA projection neurons. However, tracing studies demonstrate that the vast majority of mPFC inputs to the BLA form synapses with dendritic spines, which have been reported to exist only on projection neurons of the BLA. Here we present data that suggests a specific subclass of BLA interneurons, those that express neurokinin 1 receptors (NK-1r) are likely candidates for the inhibitory component of the feed forward inhibition described above. Here we report that, in the rat, the NK-1r containing BLA-interneurons contain dendritic spines and NMDA receptors. Furthermore, we report that in anesthetized rats disinhibition of mPFC neurons by injections of bicuculline methiodide (50 pmol), leads to cFos induction in 25 – 50% of the NK-1r containing interneurons in the BLA, while 0% of the NK-1r interneurons expressed cFos following vehicle injections. Furthermore, selective ablation of these NK-1r containing BLA-interneurons (by use of the targeted toxin, SSP-Saporin) suppressed anxiolytic-like effects of familiarity in the SI test. Collectively, these data suggest the NK-1r containing interneurons of the BLA may respond to glutamatergic inputs from the mPFC and may be involved in a mPFC-BLA anxiety or fear regulating pathway.

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What does acetylcholine do in the posterior parietal cortex (PPC)? Attentional performance-associated increases in PPC ACh efflux.

Kozak R, Parikh V, Martinez V, Brown H, Bruno JP, Sarter S (2005) What does acetylcholine do in the posterior parietal cortex (PPC)? Attentional performance-associated increases in PPC ACh efflux. Neuroscience 2005 Abstracts 644.1. Society for Neuroscience, Washington, DC.

Summary: Medial prefrontal cortex (mPFC) ACh efflux has been demonstrated to mediate attentional performance, particularly under conditions that require increases in attentional effort or the processing of distractors. Activation of the mPFC, in part as a result of cholinergic activity, is thought to orchestrate top-down effects for optimization of input processing elsewhere in the cortex. We previously demonstrated that mPFC cholinergic mechanisms influence PPC ACh efflux, suggesting that PPC ACh efflux is a component of the prefrontal circuitry mediating top-down effects. The present experiment was designed to characterize attentional performance-associated increases in PPC ACh efflux in animals performing a regular sustained attention task, following the presentation of a visual distractor, and following loss of cholinergic inputs to the mPFC. Attention task-performing animals were equipped with a guide cannula for insertion of a microdialysis probe and to collect dialysates in the PPC. Cholinergic projections to the mPFC were lesioned bilaterally by infusing 192-IgG saporin into the mPFC. Regular attentional performance was associated with increases in PPC ACh efflux that mirrored those observed previously in the mPFC. In contrast to evidence indicating a cholinergic role in the processing of distractors in the mPFC, PPC ACh efflux was not affected by the distractor and associated impairments in performance. The performance effects of the distractor were augmented in animals with mPFC cholinergic deafferentation. Performance-associated increases in PPC ACh efflux of deafferented animals were higher following the presentation of the distractor than in intact rats. These data support the hypotheses that mPFC cholinergic inputs contribute to the suppression of the effects of distractors and to the recruitment of posterior cortical cholinergic inputs to optimize processing under challenging conditions.

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

Basal forebrain cholinergic lesions produce a dissociation of impairment in delay and trace conditioning in rats

Butt AE, Cabrera S, Chavez C, Corley S, Cortez A, Figueroa J, Kitto M, Torner E (2005) Basal forebrain cholinergic lesions produce a dissociation of impairment in delay and trace conditioning in rats. Neuroscience 2005 Abstracts 644.2. Society for Neuroscience, Washington, DC.

Summary: Recent research suggests that Pavlovian trace conditioning, but not delay conditioning, requires awareness or attention, where these processes appear to depend on specific brain systems. For example, Clark, Manns, and Squire (2002) have shown that although amnesiac humans with damage to the hippocampus (HPC) acquire a normal conditioned response (CR) in delay conditioning paradigms where the conditioned stimulus (CS) and unconditioned stimulus (US) partly overlap, they fail to acquire the CR in trace conditioning paradigms where the CS and US are separated in time. Han and colleagues (2003) have shown that the anterior cingulate cortex (ACC) is similarly necessary for trace but not delay conditioning in rats. The medial prefrontal cortex (mPFC) is also involved in trace but not delay conditioning (Kronforst-Collins & Disterhoft, 1998). The basal forebrain cholinergic system (BFCS) has projections to mPFC, ACC, and HPC. Given that each of these regions is critical for trace but not delay conditioning, we hypothesized that lesions of the BFCS using 192 IgG-saporin (SAP) would selectively impair trace but not delay appetitive conditioning in rats. Rats received bilateral injections of SAP or saline only (control group) into BFCS prior to conditioning with a tone CS and sucrose pellet US in either a delay or 10 s trace conditioning paradigm. Preliminary results support this hypothesis. Compared to controls, rats in the BFCS lesion group showed moderate impairment in delay conditioning but more severe impairment in the trace conditioning paradigm. Rats in both groups showed an increase in differential responding to the CS in the delay paradigm, although the BFCS lesion group showed less conditioned responding than controls. In contrast, only the controls showed progressive differential responding to the CS in the trace conditioning paradigm. These data suggest that the BFCS contribute critically to the maintenance of attention in Pavlovian trace conditioning.

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

Role of the medial septum in a repeated acquisition task

Strait TA, Montoya D, Pang KCH (2005) Role of the medial septum in a repeated acquisition task. Neuroscience 2005 Abstracts 647.14. Society for Neuroscience, Washington, DC.

Summary: The medial septum/diagonal band of Broca (MSDB) provides a major afferent pathway to the hippocampus and both regions are important in learning and memory. The two major projection cells of the MSDB are cholinergic and GABAergic neurons. Although nonselective lesions of the MSDB impair spatial memory, the role of the different MSDB neuronal population in memory is an active area of research. In the present study, rats with preferential cholinergic or GABAergic lesions of the MSDB will be tested on the repeated acquisition task. The task assesses how well a rat can learn the location of a reward that changes from day to day. All sessions are performed on an 8-arm radial arm maze using one arm for reward. Each daily session consists of 5 trials with rats starting from a different arm on each trial. Rats are tested for a total of 9 days; each day a new rewarded arm is used. Our preliminary data suggest that rats with selective cholinergic lesions using 192-IgG saporin are not impaired in acquisition of the task. These results with selective cholinergic lesions contrast with our previous work showing that preferential GABAergic MSDB lesions impair performance of a repeated acquisition task in a water maze. We are currently investigating the effects of preferential GABAergic MSDB lesions on this task. Our preliminary data suggests that cholinergic and GABAergic MSDB neurons may have differential roles in acquisition of a spatial memory task.

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

Cholinergic therapy does not rescue spatial learning deficits induced by ICV injection of 192 IgG-saporin

Lohals R, Veng LM (2005) Cholinergic therapy does not rescue spatial learning deficits induced by ICV injection of 192 IgG-saporin. Neuroscience 2005 Abstracts 653.5. Society for Neuroscience, Washington, DC.

Summary: The cholinergic hypothesis states that central cholinergic dysfunction is responsible for age-dependent cognitive decline. To model this in rats, we induced cholinergic basal forebrain loss the neurotoxin IgG192-saporin (SAP). Following ICV infusion of 2.5 or 5 microgram (ug) SAP, or saline, rats were tested in the radial 12-arm water maze (RAWM), a spatial learning and memory task. While saline sham or 2.5 ug SAP lesioned rats showed normal learning over 4 trials in the RAWM, 5 ug SAP rats were impaired. However, when trained over 20 trials, 5 ug SAP rats eventually attained the same level of performance as 2.5 ug SAP or saline sham rats, and 28 days later all rats showed intact memory for this platform location. In the open field, 5 ug SAP rats failed to habituate. However, SAP or saline sham lesioned rats did not differ in basal activity, rotarod, or visually cued RAWM performance. SAP lesion resulted in severe depletion of ChAT activity in hippocampus and cortex, which significantly correlated with learning impairment in the RAWM. In a second experiment, we used 5 ug ICV SAP to investigate the effect of cholinergic therapy on SAP-induced spatial learning deficits in the RAWM. However, neither galantamine (0.30, 1.25, 5.0 mg/kg) nor RJR-2403 (0.08, 0.31, 1.25 mg/kg) could reverse the SAP induced deficit in RAWM learning. In conclusion, we found that spatial learning in the RAWM was consistently impaired following severe (5.0 ug SAP) cholinergic basal forebrain lesion in rats. This learning deficit was not confounded by general behavioral disturbances. However, with excessive training SAP lesioned rats could learn and later recall spatial information, suggesting that recall is intact in cholinergic lesioned animals. Severe SAP lesion also impaired habituation in an open field and this was not due to hyperactivity. Finally, treatment with galantamine and RJR-2403 did not alleviate the cognitive deficit induced by the SAP lesion, likely due to the severity of cholinergic depletion.

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The potential role of the corticopetal cholinergic system in mediating anxiogenic states in rats

Knox DK, Berntson GG (2005) The potential role of the corticopetal cholinergic system in mediating anxiogenic states in rats. Neuroscience 2005 Abstracts 659.10. Society for Neuroscience, Washington, DC.

Summary: Previous research has demonstrated that the corticopetal cholinergic system is important in mediating defensive tachycardia which suggests that this system may be important in mediating aversive states such as fear and anxiety. The aim of this study was to determine how corticopetal cholinergic lesions affect behavioral models of aversive states. The cholinergic immunotoxin 192 IgG saporin (ATS, San Diego CA) was infused into the nucleus basalis of rats in order to accomplish corticopetal cholinergic lesions. Lesioned and control rats were then evaluated on three behavioral models of anxiogenic states: behavior in the elevated plus maze, behavioral suppression induced by classical and contextual fear conditioned stimuli, and heightened arousal induced by a footshock. Lesioned and control rats did not differ on any anxiogenic behavioral measure in the elevated plus maze indicating that corticopetal cholinergic lesions did not affect behavioral indices of unconditional fear. In contrast, both classical and contextual fear conditioned stimuli induced behavioral suppression in control rats, and these effects were attenuated in lesioned rats indicating that corticopetal cholinergic lesions attenuated conditioned fear. Lastly, heightened arousal was evaluated in lesioned and control rats by monitoring behavioral suppression and changes in the electroencephalogram (EEG) over the retrosplenial cortex after a footshock. The footshock induced decreases in the integral area of the delta band and increases in the integral area of the theta band of the EEG in control rats. Both of these effects were attenuated in lesioned rats. In addition, changes in delta and behavioral suppression induced by the footshock were significantly correlated. These results indicated that corticopetal cholinergic lesions attenuated the heightened arousal induced by an aversive event. Taken together, the results of the study suggest that the corticopetal cholinergic system may be important in mediating components of anxiogenic states.

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

Characterization of an immunotoxin model of Parkinson’s disease in mice

Stead S, Trottier N, Doering LC (2005) Characterization of an immunotoxin model of Parkinson's disease in mice. Neuroscience 2005 Abstracts 664.9. Society for Neuroscience, Washington, DC.

Summary: The primary event underlying the motor deficits of Parkinson's disease (PD) is degeneration of neurons in the nigro-striatal system. The most widely employed laboratory rodent models of Parkinson's are the neurotoxin 6-hydroxydopamine (6-OHDA) model that causes acute degeneration of the dopamine neurons in the substantia nigra (SN) and the MPTP mouse model. To date, there is no single model which accurately simulates the pathogenic, histological, biochemical and clinical features relevant for the investigation of PD. Toxins conveyed by axonal transport can be used to make selective lesions in the central nervous system. As previously shown in rats (Wiley et al., Cell. Mol. Biol., 2003), we have found that selective degeneration of the SN can be induced with an immunotoxin consisting of the highly active ribosome inactivating protein Saporin linked to an antibody to the dopamine transporter. A unilateral stereotaxic injection of anti-DAT-Saporin (0.25ug/2ul and 0.05ug/2ul) into the striatum of young (6-8 weeks old) female C57BL6 mice causes a progressive reduction in the number of DA neurons in the SN in comparison to the non-lesioned hemisphere and in various controls. Furthermore, in parallel to the immunohistochemical dopamine neuron death, the animals display a pronounced circling behaviour when challenged with apomorphine (3mg/kg). We are currently examining the affected brain sections for inclusion bodies and changes in astrocytes. This model exhibits the selective deterioration of the nigro-striatal system that occurs in Parkinson's disease and provides a system to intervene at various stages of dopamine neuron loss and evaluate the effectiveness of stem cell therapy.

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Testosterone treatment prevents deficits in motor activation caused by partial loss of motoneurons

Fargo KN, Sengelaub DR (2005) Testosterone treatment prevents deficits in motor activation caused by partial loss of motoneurons. Neuroscience 2005 Abstracts 672.8. Society for Neuroscience, Washington, DC.

Summary: In male rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) project to the bulbocavernosus and levator ani muscles (BC/LA). The SNB system is dependent on androgens for its development, adult morphology, and function. We have previously demonstrated that unilateral depletion of SNB motoneurons induces atrophy of dendrites and somata in contralateral SNB motoneurons, and that this atrophy is prevented by treatment with exogenous testosterone. In the present experiment, we tested the hypothesis that this neuroprotective effect of testosterone on the morphology of SNB motoneurons is accompanied by a neuroprotective effect on the electrophysiological function of the system. We unilaterally depleted right-side SNB motoneurons by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, some of the saporin-injected rats were castrated and immediately given exogenous testosterone in subcutaneous Silastic capsules designed to produce testosterone titers in the high-normal physiological range. Four weeks later, animals were anesthetized and spinally transected. A stimulating electrode was placed on the left L6 dorsal root, which carries motor afferents from the BC/LA, and a recording electrode was placed on the motor branch of the left pudendal nerve, which carries SNB motoneuron axons to the BC/LA. Both nerves were then severed distal to electrode placement, and recruitment curves were generated by stimulating through the entire range of effective intensities. Consistent with our previously reported morphological changes, unilateral motoneuron depletion resulted in an attenuation of the recruitment of motoneurons in the contralateral SNB, and this was completely prevented by treatment with exogenous testosterone. This result provides a functional correlate to the neuroprotective effects of testosterone treatment on SNB morphology following unilateral motoneuron depletion, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.

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

Intraventricular IgG192-saporin lesions lead to altered 5-HT2A receptor levels in the hippocampus

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.

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

Pain facilitatory cells in the rostral ventromedial medulla coexpress opioid-μ receptors and cholecystokinin type 2 receptors

Zhang W, Gardell SE, Xie Y, Luo M, Rance NE, Vanderah TW, Porreca F, Lai J (2005) Pain facilitatory cells in the rostral ventromedial medulla coexpress opioid-μ receptors and cholecystokinin type 2 receptors. Neuroscience 2005 Abstracts 394.17. Society for Neuroscience, Washington, DC.

Summary: Pain transmission can be modulated by descending input to the spinal dorsal horn from the rostral ventromedial medulla (RVM). RVM neurons that facilitate nociception are termed “ON-cells”, which are inhibited by mu-opioids, suggesting that they express opioid mu receptors (MOR). Focal application of cholecystokinin (CCK8(s)) into the RVM elicits acute thermal and tactile hypersensitivity and induces ON-cell activity. In situ hybridization using riboprobes for either rat MOR or rat cholecystokinin type-2 receptor (CCK-2) confirms the expression of these receptors in the RVM. Pretreatment with a toxin conjugate, CCK8(s)-saporin results in a significant loss of CCK-2 positive cells in the RVM, concomitant with a blockade of CCK8(s) induced hyperalgesia. The pretreatment also significantly reduces the number of neurons labeled for MOR in the RVM, suggesting that MOR and CCK-2 may be co-localized in some RVM cells. Consistent with these data, similar pretreatment with the toxin conjugate, dermorphin-saporin, which selectively targets MOR expressing neurons, significantly reduces the number of MOR labeled cells in the RVM, blocks RVM CCK8(s) induced hyperalgesia and reduces the number of CCK-2 positive cells in the RVM. In situ hybridization using 35S-labeled CCK-2 riboprobes and Digoxigenin-labeled MOR riboprobes shows that over 80% of labeled RVM neurons co-express both MOR and CCK-2, ~15% express only CCK-2, and very few cells express only MOR. These findings represent the first direct demonstration of the phenotype of pain facilitatory neurons in the RVM. Together with previous studies showing that RVM CCK-2 antagonists reverse nerve injury-induced pain, this phenotype provides strong support for the view that endogenous CCK is a critical mediator of the descending pain facilitation, particularly in the maintenance of experimental neuropathic pain. Support Contributed By: NIDCR R01 DE016458

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12), CCK-SAP (Cat. #IT-31)

ATS Poster of the Year Winner

Immunotoxic destruction of catecholaminergic pathways disrupts the onset of puberty in the female rat

Vander Schaaf EB, Lusk JD, Jarrard LE, I’Anson H (2005) Immunotoxic destruction of catecholaminergic pathways disrupts the onset of puberty in the female rat. Neuroscience 2005 Abstracts 406.10. Society for Neuroscience, Washington, DC.

Summary: Ascending catecholaminergic (NE/E) pathways from the brainstem terminate near gonadotropin releasing hormone cell bodies and terminals in the hypothalamus. To determine the significance of NE/E pathways in regulating puberty onset, a neurotoxin (dopamine-ß-hydroxylase conjugated to saporin, DSAP) was administered intracerebrally to developing female rats to destroy this pathway and the timing of puberty onset was monitored. DSAP or vehicle (unconjugated saporin, SAP) was injected into the hypothalamic paraventricular nucleus on Days 23-25 of age (n=10 per group). An additional 8 rats served as untreated controls. Growth rate was monitored daily and on surgery days SAP & DSAP rats grew at a slower rate than controls. Thus, food intake of control rats was temporarily adjusted to ensure that growth rate was similar between groups. Onset of puberty and cycle length were monitored via vaginal cytology. 2-Deoxy-D-glucose-induced glucoprivation determined which rats received complete DSAP lesions, since lesioned rats do not acutely increase food intake when glucose-deprived. Results showed that NE/E neurons were adequately lesioned in seven of ten DSAP rats. Puberty onset (time of first estrus) was delayed in DSAP-lesioned rats (40.86 ± 1.79 days of age, n=7) compared to vehicle or control rats (36.25 ± 0.31 days of age, n=10; 37.50 ± 0.31 days of age, n=8). Estrous cycle length of DSAP rats (5.38 ± 0.46 days, n=7) was not significantly longer than in vehicle or control rats (4.91 ± 0.18 days, n=10; 4.40 ± 0.12 days, n=8). Thus, lesioning the NE/E pathway caused delay in onset of puberty in female rats, but no significant change in estrous cycle length. Therefore, ascending catecholaminergic pathways from the brainstem are important in determining puberty onset timing. First estrus did eventually occur in DSAP rats, suggesting that other neural pathways may be activated to regulate puberty onset and estrous cyclicity in its absence.

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

Distinct roles for amygdala central nucleus, medial prefrontal cortex, and posterior parietal cortex in attention for learning and action

Maddux JM, Chatterjee S, Kerfoot EC, Holland PC (2005) Distinct roles for amygdala central nucleus, medial prefrontal cortex, and posterior parietal cortex in attention for learning and action. Neuroscience 2005 Abstracts 411.16. Society for Neuroscience, Washington, DC.

Summary: Many theories of associative learning claim that the accuracy with which an event predicts its consequences affects the allocation of attention to that event. More reliable predictors are more likely to control action, but less reliable predictors often are more likely to capture attention for purposes of new learning about those events. Previous studies from our lab showed the amygdala central nucleus (ACe) to be important for both sustained attention guiding performance to predictive cues, and for enhanced new learning about less predictive cues. This study investigated the possibility that ACe affects these distinct aspects of attention by influencing different, specialized cortical regions, via its modulation of the basal forebrain cholinergic system. Rats were given either ibotenic acid lesions of ACe, 192 IgG-saporin lesions that reduced the basal forebrain cholinergic input to medial prefrontal cortex (mPFC) or posterior parietal cortex (PPC), or sham lesions of one of these regions. In an operant 5-choice reaction time task, responding to “CRF” ports was reinforced on 100% of the trials, whereas responding to “PRF” ports was reinforced on only 50% of such trials. Later, the ability of one CRF port and one PRF port to overshadow Pavlovian conditioning of auditory cues when port + tone compounds were paired with the delivery of a new, more valued reinforcer was examined. ACe lesions interfered with attention to the PRF cue for both learning and action, whereas reduction of cholinergic input to mPFC interfered only with attention for action, and reduction of cholinergic input to PPC interfered only with attention for new learning. The PRF port overshadowed conditioning of the tone significantly more than did the CRF port in both sham and mPFC rats, but not in ACe or PPC rats. By contrast, relative to CRF port responding, control of port-directed responding by the PRF cue was significantly greater in sham and PPC rats than in ACe or mPFC rats.

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

Experimental dissociation of neural circuits underlying anorexic and conditioned avoidance responses to LiCl in rats

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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Cortical cholinergic deficiency enhances amphetamine-induced dopamine release in accumbens

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.

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

Role of IB4-containing afferents in the effect of IT clonidine

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.

Related Products: IB4-SAP (Cat. #IT-10)

Contributions of NMDA receptors to cortical plasticity after cholinergic deafferentation

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.

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

Hypocretin/orexin neurons and the perifornical hypothalamus play a more important role in contextual fear than in restraint stress

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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On the role of the basal forebrain cholinergic neurons in regulation of recovery sleep

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.

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

Involvement of lumbar spinothalamic cells in relay of sensory cues related to vaginocervical stimulation in female rats

Coolen LM, Amstalden KAZ, Allard J (2005) Involvement of lumbar spinothalamic cells in relay of sensory cues related to vaginocervical stimulation in female rats. Neuroscience 2005 Abstracts 321.13. Society for Neuroscience, Washington, DC.

Summary: The rat lumbar spinal cord contains a population of galanin containing spinothalamic (LSt) cells, which in male rats play a pivotal role in the control of ejaculation. However, the function of LSt cells in female rats is unknown. LSt cells project to the parvocellular subparafascicular thalamic nucleus (SPFp), where Fos is expressed following vaginocervical stimulation (VCS). Hence, we hypothesize that LSt cells are involved in relay of sensory cues related to VCS to the brain. To test this hypothesis, the effects of LSt lesions were investigated on two parameters that are dependent on relay of VCS-related cues: pseudopregancy and Fos expression in the SPFp. Adult female Sprague Dawley rats received infusions of substance P-conjugated (SSP-SAP) or unconjugated saporin (control) in lumbar levels 3-4. Females were investigated for: estrous cyclicity, expression of sexual behavior, and induction of pseudopregnancy by mating with vasectomized male partners including 5, 10, or 15 intromissions. For the final test, females received 10 or 15 intromissions from male partners, were perfused one hour later, and brains and spinal cords were examined for Fos expression and LSt lesions. SSP-SAP treatment resulted in severe reduction of LSt cells, but did not affect cyclicity or expression of sexual behavior, suggesting that LSt cells are not involved in regulation of these functions. In contrast, LSt lesions significantly reduced mating-induced Fos expression in the SPFp, supporting the involvement of LSt cells in relay of VCS-related sensory information to the SPFp. However, LSt lesions did not prevent mating-induced pseudopregancy and only partly blocked mating-induced neural activation in SPFp, indicating the possible involvement of alternate pathways. Alternatively, the few remaining LSt cells in lesioned females are sufficient for induction of Fos in SPFp and pseudopregnancy.

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

Ablation of NK-1 receptor-expressing interneurons prevents methamphetamine-induced apoptosis but not dopamine terminal toxicity in the striatum of mice

Xu, WZhu JPQ, Angulo JA (2005) Ablation of NK-1 receptor-expressing interneurons prevents methamphetamine-induced apoptosis but not dopamine terminal toxicity in the striatum of mice. Neuroscience 2005 Abstracts 337.9. Society for Neuroscience, Washington, DC.

Summary: Pharmacological evidence from our laboratory demonstrates that the neurokinin-1 (NK-1) receptor mediates methamphetamine (METH)-induced toxicity of the dopamine terminals and the apoptosis of some striatal neurons. We have shown that systemic administration of the NK-1 receptor antagonist, WIN 51,708, prior to METH exposure, can protect the striatum from METH-induced damage at pre- and post-synaptic sites. To further assess the role of the NK-1 receptor on METH-induced striatal neural damage, NK-1 receptor-expressing interneurons were selectively ablated by means of intrastriatal injections of [Sar9,Met(O2)11]substance P conjugated to the ribosomal-inactivating cytotoxin saporin (SSP-SAP). TUNEL-labeling showed that ablation of striatal neurons that express NK-1 receptors provided protection against METH-induced apoptosis of some striatal neurons. However, ablation of NK-1 receptor-expressing interneurons did not provide protection against METH-induced depletion of tyrosine hydroxylase, a reliable marker of the dopamine terminals of the strtiatum. These results suggest that METH-induced apoptosis and dopamine terminal toxicity occur via distinct mechanisms in the mouse striatum.

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Sortilin and p75NTR: localization in adult rat brain and their alterations following pharmacological manipulations

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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Medial-septal cholinergic denervation leads to synaptic glutamatergic dysfunction in hippocampus

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.

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

Selective ablation of non-peptidergic C-fibers using IB4-saporin as a tool to identify the functional role of these fibers in pain transmission

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.

Related Products: IB4-SAP (Cat. #IT-10)

Adenosine levels do not increase with 6 h waking in rats with lesions of the lateral hypothalamus

Gerashchenko D, Murillo-Rodriguez E, Blanco-Centurion C, Lin L, Nishino S, Mignot E, Shiromani PJ (2005) Adenosine levels do not increase with 6 h waking in rats with lesions of the lateral hypothalamus. Neuroscience 2005 Abstracts 63.9. Society for Neuroscience, Washington, DC.

Summary: The hypocretin neurons in the lateral hypothalamus (LH) have been implicated in wakefulness, but it is not clear which projection is responsible for the arousal. One possibility is that the LH neurons induce wakefulness by driving the basal forebrain (BF) wake-active neurons (Gerashchenko and Shiromani, Cellular & Molec Neurosci, 29: 41, 2004). Here we measure adenosine (AD) levels in the BF as a marker of arousal and test the LH-BF circuit in Sprague-Dawley rats with lesions of the LH induced by hypocretin-2-saporin. 64 days after lesions the rats were kept awake (gentle handling) for six hours (ZT 3-9) and microdialysis samples (5ul) were collected hourly for 9 hours (24h after probe stabilization). AD levels were assessed using HPLC. Hypocretin-saporin ablated 95% of the hypocretin neurons and reduced CSF hypocretin levels (-75% versus control). AD levels increased with 6h waking in saline control rats (n=9), consistent with previous studies in cats (Strecker et al., Behav Brain Res 115: 183, 2000) and rats (Murillo-Rodriguez et al., Neuroscience 123: 361, 2004). However, in rats with LH lesions (n=5) such an increase with waking did not occur. Sleep drive was measured by conducting a rodent version of a multiple sleep latency test (MSLT). In this test, conducted over 10h (from ZT2-ZT12) the rats were kept awake for 20min and then allowed 20min to sleep. The lesioned rats had more sleep during the 20min sleep periods indicating a higher sleep drive. These results suggest that in narcolepsy when the HCRT LH neurons die, there is a loss of stimulation of the wake-active BF neurons and the decline in this pathway may be the cause of the increased sleep attacks. Supported by VA Medical Research and NIH

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