sfn2006

43 entries

The role of septo-hippocampal cholinergic lesion, place versus response strategy, and acquisition of a delayed matching to position T-maze task

Fitz NF, Gibbs RB, Johnson DA (2006) The role of septo-hippocampal cholinergic lesion, place versus response strategy, and acquisition of a delayed matching to position T-maze task. Neuroscience 2006 Abstracts 751.20. Society for Neuroscience, Atlanta, GA.

Summary: Previously we showed that loss of cholinergic input to the hippocampus results in a significant impairment in acquisition of a delayed matching-to-position T-maze task. Further studies suggest that rats adopt different strategies during different stages of acquisition, initially using a response-type strategy or side preference strategy (independent of external cues) and then switching to a more efficient place strategy (reliant on external cues). We hypothesized that animals with lesions of hippocampal cholinergic inputs would have difficulty shifting to a place strategy, resulting in more days using a response-type strategy, and resulting in the deficit in acquisition. Male Sprague-Dawley rats received intraseptal infusions of either artificial cerebrospinal fluid (CSF) or the selective cholinergic immunotoxin, 192 IgG-saporin (SAP; 0.2 μg in 1.0 μl) into the medial septum (MS). Following recovery from surgery, animals were trained in a DMP T-maze task that consisted of learning to return to an arm of the maze that had been explored during a previous trial. Typically, in both treatment groups, rats would initially adopt a strategy of selecting an arm that resulted in a consistent turn (left or right), which was independent of external cues (response-type strategy). Later in training, the animals adopted a strategy that required a turn that was dependent on external cues (place strategy). Compared to controls, SAP animals had a loss of hippocampal cholinergic innervation and an increase in the number of days to reach criterion (21.7 ± 1.6 days vs. 15.9±0.5 days, p < 0.05). For the SAP group, the increased days to criterion was due to a significant increase in the number of days animals used the response-type strategy (14.8 ± 1.8 days vs. 8.1 ± 1.7 days, p < 0.05). There was no significant difference between groups in the number of days animals utilized the place strategy. These data are consistent with the hypothesis that the cause of the learning impairment on the DMP task observed following cholinergic deafferentation of the hippocampus is due to an impairment in the ability to shift from a response-type strategy to a place strategy.

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Rodent models: Autism and fragile x syndrome

Walker BR, Klueger K (2006) Rodent models: Autism and fragile x syndrome. Neuroscience 2006 Abstracts 764.6. Society for Neuroscience, Atlanta, GA.

Summary: While the exact etiology of autism is not known, autism spectrum disorders (ASD) are most commonly characterized by behavioral deficits in social interaction and communication, obsessional mannerisms, behavioral inflexibility, impairments in planning, attention, hyperactivity and a lack of environmental awareness. These behavioral characteristics have been theorized to be the result of altered forebrain and/or cerebellar circuitry and neurotransmitter transmission. There is some evidence to suggest that treatments effective against seizure and mood disorders that alter these specific neuronal populations are also effective against some core behavioral characteristics of persons with ASD. Therefore, in the present study we tested the hypothesis that electrical stimulation of the rat vagus nerve, as it enters the nucleus tractus solitarius (NTS), will ameliorate social behavior deficits caused by forebrain ACh lesions. To this end, we measured social interaction behavior in rats following bilateral i.c.v. injection of 192-IgG saporin (192-sap; 2 µg/side) or saline, and again following electrical stimulation of the vagus nerve/NTS (100-900 microA). As shown by us previously, bilateral 192-sap injections created a significant decrease in social behavior, as compared to controls. Electrical stimulation of the vagus/NTS, however, reduced these social deficits in 192-sap rats, while having no effect on the social interaction of sham controls. These findings suggest that the circuitry mediating the behavioral deficits seen in autism and ASD may functionally overlap with circuitry of seizure and mood disorders. In addition, our results suggest that vagal nerve stimulation (VNS) may be effective in reducing some of these core behavioral features seen in autism and ASD.

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

Impaired cortical plasticity after early hypoxia–ischemia

Failor SW, Evans MM, Cang J, Stryker MP, McQuillen PS (2006) Impaired cortical plasticity after early hypoxia–ischemia. Neuroscience 2006 Abstracts 717.14. Society for Neuroscience, Atlanta, GA.

Summary: Background: Unique forms of structural plasticity occur in sensory cortex during critical periods in the developing brain. Recovery from neonatal hypoxic-ischemic brain injury may involve plasticity mechanisms. Objective: To investigate the effect of hypoxic-ischemic injury on plasticity, we examined quantifiable forms of use-dependent structural thalamocortical plasticity in somatosensory and visual cortex following early cerebral hypoxia-ischemia (HI) within a rodent model. Methods: Plasticity in primary somatosensory cortex (S1) was induced by lesion of whisker pad row C on selective days during the first postnatal week with or without preceding hypoxia-ischemia (HI, Vannucci model). The whisker barrel map was visualized with cytochrome oxidase staining and 5-HT immunohistochemistry and quantified by measuring the ratio of D-row to C-row areas in tangential sections. Plasticity in primary visual cortex (V1) was induced by 4-day monocular deprivation (MD) beginning at postnatal day (PND) 28. Ocular dominance was quantified using intrinsic signal optical imaging and expressed as an index of the response to right or left eye stimulation, with or without MD and/or preceding early HI. Changes in markers of inhibitory neurons, extracellular matrix and myelin-associated molecules following HI are correlated with plasticity measurements. Results: S1 plasticity following neonatal HI is attenuated throughout the critical period (PND 1-3). S1 plasticity is significantly decreased (P<0.01, all ages) by an average of 66%. HI does not affect timing of the critical period for S1 plasticity. Following MD, the ocular dominance index (ODI) decreases from 0.14 +/- 0.12 (mean +/- SD, n=9) to -0.16 +/- 0.18 (n=5). Following neonatal HI, this ODI shift is attenuated (n=2). Similar respective effects following MD are observed using a selective immunotoxin (192-saporin) to destroy subplate neurons underlying visual cortex (n=6). Conclusions: Neonatal cerebral hypoxia-ischemia impairs structural plasticity in primary somatosensory and visual cortex. Similar results following selective immunoablation of subplate neurons, taken together with prior observations of selective subplate neuron death following neonatal HI, suggests a role for subplate neurons in structural plasticity during critical periods in sensory cortex.

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Transplant of hypocretin neurons into the lateral hypothalamus of rats with lesions of the hypocretin neurons

Hernandez-Martinez H, Arias-Carrion O, Drucker-Colin R, Murillo-Rodriguez E (2006) Transplant of hypocretin neurons into the lateral hypothalamus of rats with lesions of the hypocretin neurons. Neuroscience 2006 Abstracts 719.2. Society for Neuroscience, Atlanta, GA.

Summary: Narcolepsy, a disabling neurological disorder is characterized by excessive daytime sleepiness, sleeps attacks, sleep fragmentation, and cataplexy. This sleep disorder has been linked to a loss of neurons containing the neuropeptide hypocretin (HCRT). Our group has developed an experimental model to induce narcolepsy in rats. The bilateral administration of the neurotoxin hypocretin-2-saporin (HCRT2-SAP) into the lateral hypothalamus (LH) of rats destroys the HCRT neurons. Therefore, the loss of HCRT neurons leads to developing narcolepsy. In order to replace the HCRT lost neurons by HCRT2-SAP, a suspension of cells from the posterior hypothalamus of 3-5 days old rat pups were stained with GFP and injected into the LH of lesioned rats. Animals were sacrificed 21 days after transplant, and cryostat-cut coronal sections of the LH sections were examined for presence of HCRT-immunofluorescence neurons. Preliminary data shows that HCRT transplanted neurons into the LH of lesioned rats were present at the target area 21 days after implant. These somata were similar in size and appearance to adult rat HCRT-immunoreactive neurons. Our results indicate that HCRT neurons obtained from rat pups can be grafted into a host brain and graft survives during 21 days. Importantly, our study addresses the possibility to replace HCRT neurons in narcolepsy in order to reverse this disease.

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The effects of a norepinephrine reuptake blocker, atomoxotine, on an attentional set shifting impairment caused by prefrontal lesions

McGaughy JA (2006) The effects of a norepinephrine reuptake blocker, atomoxotine, on an attentional set shifting impairment caused by prefrontal lesions. Neuroscience 2006 Abstracts 749.17. Society for Neuroscience, Atlanta, GA.

Summary: There is substantial evidence to support the role of norepineprhine (NE) in selective attention. The NE system is hypothesized to maintain task-related attentional focus and allow shifts of attention (Aston-Jones and Cohen, 2005). These unique attentional functions correlate with changes in the firing patterns in locus coeruleus. Previous work in our lab has shown that NE lesions of the medial prefrontal cortex produces robust impairments in the ability of rats to perform an attentional set-shift, though acquisition of the attentional set and reinforcement reversal learning were spared. The current study assesses the effectiveness of atomoxotine, a NE reuptake blocker, in remediating these deficits. This drug is currently used in the treatment of attention deficit disorder and may restore balance to the noradrenergic system of the frontal cortex in these patients. Male, Long-Evans rats received lesions of the medial wall of the prefrontal cortex using dopamine beta-hydroxylase saporin (DBH-SAP) to produce selective noradrenergic deafferentation. The performance of DBH-SAP rats was compared to sham-lesioned (SHAM) rats in a test of attentional set-shifting after intraperitoneal injections of atomoxotine (0.0, 0.1,0.3, 0.9 mg/kg) 15 minutes prior to the test of attentional set-shifting. During the attentional set shifting task (Birrell and Brown 1999), rats were exposed to complex stimuli (texturized, scented pots filled with digging media). Initially rats were reinforced for focusing attention on one stimulus dimension, e.g. scent, during the tests of complex discriminations and reinforcement reversals. In tests of attentional set-shifting, subjects were required to inhibit attention to the previously reinforced dimension e.g. scent and learn that a new dimension e.g. texture predicted reinforcement.These results confirm that NE deafferentation of prefrontal cortex impairs the ability of rats to shift attention from the initially reinforced dimension to another dimension, e.g. when texture not odor now predicts reinforcement. Low doses of atomoxotine ameliorate the set-shifting impairments of DBH-SAP rats but hindered the performance of SHAM rats. These data suggest that shifts of attentional set require an optimal level of release of NE in the frontal cortex with both high and low levels of NE causing impairments in these abilities.

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Cell type specificity of the c-Fos immunoreactive neurons of cortical layer IV after patterned visual stimulation

Vaucher EJ, Dotigny F (2006) Cell type specificity of the c-Fos immunoreactive neurons of cortical layer IV after patterned visual stimulation. Neuroscience 2006 Abstracts 545.28. Society for Neuroscience, Atlanta, GA.

Summary: The cortical processing of specific visual stimuli may be enhanced or suppressed by neuromodulators, such as acetylcholine or norepinephrine as early as in the primary visual area. We have recently shown using c-Fos immunoreactivity that the specific lesion of basal forebrain cholinergic projections abolished the visually-induced neuronal activity of the layer IV of the primary visual cortex. The present study investigated further which cell types immunoreactive for c-Fos were modulated by the cholinergic afferents. Twenty male Long Evans Rats (275-300g) were anaesthetized with urethane (1.3g/kg). C-Fos immunocytochemistry was used as a single cell resolution marker of functional activity induced by sinusoidal grating in the visual cortex in control condition, specific lesion of the cholinergic fibers using 192-IgG saporin, muscarinic inhibition by scopolamine (1mg/kg) or NMDA receptors inhibition by CPP (10mg/kg). c-Fos/Parvalbumin and c-Fos/rat-brain-pyramidal-cells-marker double immunocytochemistry was performed to determine the localization of the visually-induced c-Fos immunoreactivity within the GABAergic interneurons or pyramidal cells of the layer IV of the rat cortex. The results demonstrated that the c-Fos immunoreactivity evoked by patterned stimulation in layer IV was rarely (less than 5%) co-localized with either parvalbumin or rat-brain-pyramidal-cells-marker. In addition, this functional activity was blocked by a cholinergic deficit but was independent of NMDA receptors transmission, since their inhibition by CPP did not affect the activity-dependent c-Fos immunoreactivity. These results suggest an effect of the patterned visual stimulation and the cholinergic fibers on the excitatory spiny stellate cells rather than the GABAergic or pyramidal cells. It suggests a role of the basal forebrain cholinergic neurons in the modulation of the thalamo-cortical transmission rather than local cortical microcircuitry in the rat visual cortex.

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

Effects of selective cholinergic NBM lesions on short-interval timing

Miller JP, McAuley JD, Pang KC (2006) Effects of selective cholinergic NBM lesions on short-interval timing. Neuroscience 2006 Abstracts 572.24. Society for Neuroscience, Atlanta, GA.

Summary: The nucleus basalis magnocellularis (NBM) and its connection to the frontal cortex are important for timing short durations and divided attention. Although the NBM provides the major cholinergic input to the frontal cortex, GABAergic and other neurons are also located in the NBM and project to neocortex. To examine the role of the NBM in timing and attention, previous investigators used non-selective lesions of the NBM using ibotenic acid (IBO). In the present study, we examined the importance of cholinergic NBM neurons in timing using the selective immunotoxin 192-IgG saporin (SAP). Fisher 344 rats were trained on a peak-interval (PI) procedure using fixed-intervals of 12 s and 24 s. Once trained, stereotaxic surgeries where conducted on the rats and either SAP or nothing (SHAM) was administered into the NBM to create selective cholinergic or control lesions respectively. Preliminary results show that SAP did not alter peak times (SHAM: 11.82 s & 22.59 s versus SAP: 11.98 s & 22.88 s) or coefficient of variability (CV, SHAM: 0.41 & 0.45 versus SAP: 0.44 & 0.47). However, upon inspection of the brains, SAP lesions did not reduce the number of cholinergic neurons in the NBM. In a separate study using the PI procedure with a single fixed-interval of 18 s, IBO altered timing accuracy as measured by the absolute difference in peak times (pre-op versus post-op: SHAM = 0.60 s; IBO = 1.94 s) and altered variability as measured by the change in CV (pre-op versus post-op: SHAM = 0.02; IBO = 0.20). Preliminary results with IBO showing a non-directional reduction in accuracy are different from previous studies that have reported systematic overestimation of duration, although in our study the damage caused by IBO was restricted to the anterior NBM. Current studies are further evaluating the role of NBM neurons in timing with more selective and complete cholinergic lesions using SAP and more complete non-selective lesions using IBO.

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

Molecular changes in the dorsal horn that maintain inflammatory hyperalgesia are similar to those generated during long-term potentiation

Wong YM, Webber MJ, Dickenson AH, Hunt SP (2006) Molecular changes in the dorsal horn that maintain inflammatory hyperalgesia are similar to those generated during long-term potentiation. Neuroscience 2006 Abstracts 642.17. Society for Neuroscience, Atlanta, GA.

Summary: The generation of LTP in deep dorsal horn neurons by noxious stimulation may be one mechanism whereby acute pain transforms into a chronic pain state. Spinal LTP requires the activation of a subset of superficial dorsal horn neurons that express the neurokinin-1 receptor (NK1-R) and are crucial for the initiation and maintenance of chronic pain states. These neurons participate in local spinal sensory processing and are the origin of a spino-bulbo-spinal loop that drives descending spinal facilitation. Spinal LTP is correlated with increased neuronal expression of the transcription factor zif268 in the superficial dorsal horn. Here, we examined if inflammatory pain states required LTP-like changes in gene expression that are dependent upon an intact lamina I pathway. We also asked if changing levels of zif268 regulated the glucocorticoid receptor (GR) gene, a downstream target of zif268. NK1 expressing neurons in lamina I of the lumbar spinal cord were selectively ablated using SP-SAP applied intrathecally. 28d later, rats were injected with Complete Freunds’ Adjuvant (CFA) (50%, 100μl) 2h prior to perfusion with 4% paraformaldehyde. Using immunohistochemistry, we found that while levels of c-fos immunoreactivity were unchanged by lamina I ablation, the levels of zif268 had decreased by 36% (p<0.05) compared to controls. We therefore treated rats intrathecally with zif268 antisense or missense oligonucleotides (0.16μg/μl/h) via implanted osmotic mini pumps and assessed the behavioural effects of zif268 ‘knockdown’ on inflammatory hyperalgesia. Animals were perfused 4 days after CFA inflammation and protein levels of zif268 and GR were assessed by immunohistochemistry. Antisense, but not missense zif268 treatment, reduced the levels of zif268 by 37% and reduced behavioural allodynia by 40%, but only at days 2-4 post CFA. Levels of GR were also reduced by 30% following zif268 antisense treatment. We therefore applied antisense and missense GR probes intrathecally.This reduced the inflammatory hyperalgesia score by 38% but again only on days 2-4. These results suggest the zif268 gene is essential for the maintenance but not the induction of inflammatory pain states and that zif268 can regulate GR in the spinal cord.

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Role of spinal cord µ-opioid receptor expressing dorsal horn neurons in morphine analgesia

Kline IV RH, Wiley RG (2006) Role of spinal cord µ-opioid receptor expressing dorsal horn neurons in morphine analgesia. Neuroscience 2006 Abstracts 643.19. Society for Neuroscience, Atlanta, GA.

Summary: The role of spinal cord μ-opioid receptor expressing dorsal horn neurons in morphine analgesia is not clearly understood. Using lumbar intrathecal (i.t.) injections of the targeted toxin dermorphin-saporin to selectively destroy these cells, we sought to determine the effect of this lesion on the antinociceptive activity of systemic and i.t. morphine on the hotplate test. We examined the antinociceptive effects of morphine across a range of stimulus intensities (44, 47 & 52oC) in order to assess responses mediated by C or Aδ thermal nociceptors. Experiment 1 (systemic morphine): Sixteen Sprague Dawley male rats were injected with 500ng dermorphin-saporin i.t. or PBS and hotplate testing resumed one week after injections. Baseline hotplate responses were monitored for three weeks after which systemic morphine dose response curves (0, 2.5, 5, &10 mg/kg s.c.) were performed. Experiment 2 (spinal intrathecal morphine): Twelve Long Evans female rats were surgically implanted with indwelling lumbar i.t. catheters (8.5cm), underwent baseline hotplate testing for 7 days, had i.t. morphine dose response curves (0, 0.01, 0.1, & 1 μg) performed at 44 & 52oC seven days before and eight days after dermorphin-saporin injections. The dependent measures for the hotplate test were: 1) latencies to the first lick or guard response (all temperatures) and 2) the cumulative durations and amounts of licking and guarding events (44 and 47oC). Loss of lamina II MOR-expressing dorsal horn neurons after dermorphin-saporin was confirmed in spinal cord sections from each rat stained for MOR1 and MOR1C using standard immunoperoxidase techniques on adjacent 40 μm sections from the L4 spinal segment. Baseline responses to noxious heat did not decrease after i.t. dermorphin-saporin. The antinociceptive activity of systemic morphine was attenuated in dermorphin-saporin treated rats at 44 & 47oC; this effect was least striking on the 52oC hotplate and greatest on the 44oC hotplate. The dermorphin-saporin-induced lesion reduced the antinociceptive effects of intrathecal morphine more than systemic morphine. Based on the above findings are others not included here, we conclude that dorsal horn MOR expressing neurons are necessary for morphine to exert its maximum antinociceptive and analgesic effects.

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Astrocytic reaction to a lesion, under hormonal deprivation

Miller A, Martinez L, De LaCalle S (2006) Astrocytic reaction to a lesion, under hormonal deprivation. Neuroscience 2006 Abstracts 660.1. Society for Neuroscience, Atlanta, GA.

Summary: The basal forebrain cholinergic system plays an essential role in cortical plasticity and functional recovery following brain injury, although the precise mechanism is not known. Earlier studies from our laboratory have suggested that estrogen may have a protective effect on the basal forebrain cholinergic system, particularly in the maintenance of neuronal architecture. Although there is evidence for direct actions of estrogen on cholinergic neurons in vitro, the contribution of local glial cells to neuronal repair in this cell group, in vivo, has not been documented. We hypothesized that estrogen could also mediate neuronal repair through a modulatory effect on the activation of reactive astrocytes. Young adult female rats (n=28) were used in these studies, 14 were ovariectomized and the rest were left intact. All animals received a unilateral injection of 200 nl of the immunotoxin 192 IgG-saporin into the nucleus of the horizontal limb of the diagonal band of Broca (HDB). One month after the lesion, half of the animals in each group were implanted subcutaneously with a pellet releasing estrogen or placebo (n=7 per group) for 60 days. Using immunocytochemistry with an antibody against glial fibrillary acidic protein (GFAP), a specific marker for astrocytes, we studied changes in the expression of GFAP in the basal forebrain at the end of the treatment. Image analysis of histological sections revealed that GFAP levels in the side of the lesion were slightly higher that in the corresponding contralateral intact side. Overall change in GFAP expression in the ovariectomized animals treated with estrogen was not significantly different from the non-ovariectomized controls. In the ovariectomized animals treated with placebo (therefore undergoing a 3 month estrogen deprivation), levels of GFAP on the lesioned side were 20% higher than in controls. These results suggest that estrogen may prevent activation of astrocytes after a lesion, and perhaps allow a regenerative remodeling process to occur.

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

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