sfn2007

Frachette M, Rennie K, Pappas BA (2007) Neonatal cholinergic lesion and environmental enrichment:behavior, neurogenesis and CA1 cytoarchitecture. Neuroscience 2007 Abstracts 691.9/M9. Society for Neuroscience, San Diego, CA.

Summary: The effects of neonatal cholinergic lesion and environmental enrichment on rat behaviour and hippocampal morphology were determined. Rats were injected with the immunotoxin 192 IgG- saporin (192S) on postnatal day 7, selectively lesioning forebrain cholinergic neurons as shown by their loss of acetylcholinesterase staining and p75NTR immunoreactive (IR) neurons. After weaning, the rats were placed in enriched or standard housing for 42 days. Enriched rats, regardless of whether or not they had received 192S, subsequently showed significantly enhanced performance on the working memory version of the Morris water maze. The lesion had no effect on spatial learning. However, the lesion significantly reduced doublecortin (DCX) IR cells in the dentate gyrus, indicating reduced hippocampal neurogenesis. Enrichment did not affect the number of DCX IR cells in lesioned rats whereas there was an apparent trend towards increased cells in non-lesioned rats. The number of DCX IR neurons in the enriched and impoverished lesion groups were identical and both were significantly less than the average for the enriched non-lesioned mean, suggesting that the lesioned rats were resistant to the effects of enrichment on neurogenesis. As shown by quantitative analysis of Golgi stained CA1 neurons, the cholinergic lesion affected CA1 cell morphology, reducing apical branches and total basal branch length. This was not prevented by enrichment. There were also a number of other effects selective for certain branches but these effects tended to be observed equally often in impoverished and enriched rats. In other words, the consequences of the cholinergic lesion were immune to the housing condition. Enrichment had several effects on hippocampal cytoarchitecture but these were selective for certain branch orders rather than global alterations. The most interesting consequence of enrichment, in terms of its implication for synapse density and information processing capability, was the increased spine density and spine number observed on some branches of the apical tree. This was evident only in the non-lesioned rats. Thus, neonatal cholinergic forebrain lesion reduces dentate gyrus neurogenesis, alters CA1 dendritic morphology but has no effect on spatial learning/memory. It also renders rats unresponsive to the effects of enrichment on dentate gyrus neurogenesis, CA1 dendritic spine morphology but not spatial learning/memory.

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

Rennie KE, Frechette M, Pappas BA (2007) Behavioural consequences of combined cholinergic lesion and chronic cerebral hypoperfusion in rats. Neuroscience 2007 Abstracts 698.16/R26. Society for Neuroscience, San Diego, CA.

Summary: Chronic cerebral hypoperfusion compromises the health of hippocampal neurons, leading to a slowly emerging loss of pyramidal cells accompanied by spatial memory impairments in rats. Recent research suggests that vascular abnormalities resulting in insufficient cerebral blood flow or impaired nutrient delivery to the brain represent a significant risk factor for Alzheimer’s disease (AD) and may contribute to its pathogenesis. AD is also characterized by dysfunction of the forebrain cholinergic system. Since there is evidence that this system is involved in the control of local cerebral blood flow, we hypothesized that there would be synergistic effects of chronic cerebral hypoperfusion and cholinergic dysfunction. Hence, the aim of this study was to determine whether cholinergic dysfunction exacerbates the effects of cerebral hypoperfusion. Female rats were subjected to forebrain cholinergic lesion or control surgery by intraventricular infusion of the immunotoxin 192-IgG-saporin (192S) or phosphate buffered saline (PBS) on postnatal day 7. Six months later the rats underwent permanent bilateral occlusion of the carotid arteries (2VO), which causes moderate, chronic cerebral hypoperfusion, or sham surgery. When exposed to an open field 48, 72 and 96 hours after 2VO or sham surgery, the groups did not differ on measures of overall activity. However, the cholinergic lesion increased the latency to enter the centre area, and reduced both the number of centre entries and the percentage of total distance that was traveled in the inner squares. The lesion effects were mainly seen in the combined 192S/2VO group while 192S or 2VO alone produced only minor behavioural changes. Elevated plus testing 2 weeks after surgery revealed a reduction in open but not closed arm entries due to the cholinergic lesion. Interestingly, the effects of 2VO were dependent on the status of the cholinergic system. 2VO increased open arm entries in the PBS group, but decreased this behaviour in the 192S group. Thus on both the open field and elevated plus maze, the cholinergic lesioned rats displayed more anxious behaviour, particularly after 2VO. Finally, cholinergic lesion produced impairments on the working memory version of the Morris water maze. Again, this effect was most pronounced in the combined 192S/2VO group. This effect is unlikely to be due to motivational or sensorimotor deficits as all groups performed similarly on a cued platform version of the maze. Cholinergic lesion and 2VO appear to act synergistically to produce behavioural alterations, even at relatively early time points after 2VO. Their combined effects on CA1 pyramidal cell viability are currently under examination.

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

McAuley J, Pang K (2007) Effects of NBM lesions on selective attention in an interval timing task. Neuroscience 2007 Abstracts 742.9. Society for Neuroscience, San Diego, CA.

Summary: Divided and sustained attention are impaired by damage to the nucleus basalis magnocellularis (NBM), which provides cholinergic and GABAergic input to the neocortex. The present study was performed to further investigate the role of the NBM in attention using a selective attention version of the peak-interval timing procedure. Male Fisher 344 rats were initially trained using a peak interval procedure to time a light stimulus, delivering reward for the first lever press after 12 s. Selective attention was then tested in distracter sessions where random tone bursts and house light flashes were presented on some trials, but not others. These distracter sessions were interleaved with non-distracter sessions that were identical to initial peak-interval training. Preliminary results in normal young rats show that peak times on un-reinforced probe trials with distraction were lengthened as compared to probe trials without distraction in the same session. Moreover, peak times on non-distracter probe trials were similar between distracter and non-distracter sessions. In these preliminary studies, the observed overestimation of time during selective attention testing was transient, supporting the view that attention modulates the rate of an internal clock. Current studies aim to determine the influence of selective cholinergic or GABAergic NBM lesions in this selective attention task.

Related Products: GAT1-SAP (Cat. #IT-32)

Butt AE, Amodeo D, Flesher M, Marsa K, Holt R, Lladones R, Olney R, Haynes J, Kinney-Hurd BL, Dach N (2007) 192 IgG-saporin lesions of the cholinergic basal forebrain disrupt selective attention and trace conditioning but spare delay and long-delay conditioning. Neuroscience 2007 Abstracts 424.9/HHH8. Society for Neuroscience, San Diego, CA.

Summary: Recent research suggests that Pavlovian trace conditioning, but not delay conditioning, is a form of declarative memory that requires attention, where both of these processes depend on specific brain systems. For example, past research has 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. Others have shown that the anterior cingulate cortex (ACC) in rats and the medial prefrontal cortex (mPFC) in rabbits are similarly necessary for trace but not delay conditioning. The basal forebrain cholinergic system (BFCS) has projections to the 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 or long-delay appetitive conditioning in rats. Additionally, given evidence suggesting BFCS involvement in attention, it was hypothesized that the addition of varying levels of distraction during the trace conditioning task would cause progressively greater degrees of impairment in the BFCS lesion groups compared to controls. In contrast, neither the control groups nor the BFCS lesion groups were expected be negatively affected by the addition of a distracting stimulus in the delay and long-delay conditioning tasks. Rats received bilateral SAP lesions or sham lesions of the BFCS prior to conditioning with a white noise CS and sucrose pellet US in either a delay, long-delay, or 10 s trace conditioning paradigm. Separate groups of BFCS lesion and control rats were subjected to varying levels of visual distraction (flashing house light) in each paradigm; no distraction, low distraction (continuously blinking light), and high distraction (intermittent, unpredictable flashing light). Results supported our hypotheses, with the BFCS lesion groups showing normal delay and long-delay conditioning regardless of level of distraction. In contrast, trace conditioning was impaired in the BFCS lesion groups, with progressively greater degrees of impairment occurring with greater levels of distraction, and complete disruption of learning in the high distraction condition. Together, these experiments suggest that the BFCS is necessary for normal trace conditioning, and that the BFCS is critically involved in selective attention tasks where animals must discriminate relevant stimuli from distracting background stimuli.

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

Likhtik E, Popa D, Apergis-Schoute J, Fidacaro GA, Pare D (2007) Lesion of intercalated (ITC) amygdala neurons interfere with extinction of classically conditioned fear responses. Neuroscience 2007 Abstracts 426.6/HHH29. Society for Neuroscience, San Diego, CA.

Summary: The acquisition of conditioned fear responses (CRs) is thought to involve the potentiation of synapses conveying information about the conditioned stimulus (CS) to the basolateral (BLA) amygdala. Expression of CRs would depend on the transfer of potentiated CS inputs by the BLA to the central amygdala (CE). In contrast, the mechanisms of extinction remain controversial. It has been proposed that ITC neurons, which receive BLA inputs and generate feedforward inhibition in CE, are in a key position to mediate extinction. In this view, NMDA-dependent potentiation of BLA inputs to ITC cells during extinction training, would dampen the impact of CS-related BLA activity on CE neurons, inhibiting CRs. However, this idea is difficult to test because ITC cells occur in small, lateromedially dispersed clusters, making conventional lesioning methods inadequate. Here, we took advantage of the fact that, compared to the rest of the amygdala, ITC cells express a much higher concentration of mu opioid receptors (muORs). As a result, we could lesion them by performing local injections of a peptide-toxin conjugate (demorphin conjugated to saporin, D-Sap) that selectively targets cells expressing muORs. Control rats received injections of saporin conjugated to a blank peptide (B-Sap). On Day 1, intact rats were subjected to a standard cued fear conditioning protocol in context A. On Day 2, they received 20 CS alone presentations in a different context (B). On Day 3, rats then received either D-Sap or B-Sap injections in the ITC cell masses. One week later, extinction recall was tested in context B with 10 CS alone presentations. Compared to control (B-Sap) rats (n=10), ITC-lesioned rats (n=5) had an extinction deficit (ANOVA, F=11.687, p = 0.005). Post-hoc t-tests comparing % time freezing during the first five or last five CSs revealed that rats with ITC lesions had significantly higher freezing levels throughout the extinction recall test (p<0.002 for both tests). These differences were not attributable to a non-specific increase in freezing or anxiety levels as exploratory behaviors in a novel open field in control and ITC-lesioned rats were indistinguishable. Overall, these results indicate that ITC cells are involved in the expression of extinction.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12), Blank-SAP (Cat. #IT-21)

Arias-Carrion O, Hernandez-Martinez H, Drucker-Colin R (2007) Hypocretin/orexin neuronal loss increases adult neurogenesis. Neuroscience 2007 Abstracts 456.14/C7. Society for Neuroscience, San Diego, CA.

Summary: Adult neurogenesis in the subventricular zone (SVZ) is subjected to physiological regulation and can be modified by brain injuries. The sleep disorder narcolepsy may now be considered a neurodegenerative disease, as there is a massive reduction in the number of neurons containing the neuropeptide, hypocretin (HCRT). In the present study, we investigate the relationship between hypocretin neuronal loss and adult neurogenesis. The neurotoxin, hypocretin-2-saporin (HCRT2-SAP), was administered bilaterally to the lateral hypothalamus (LH) to lesion HCRT neurons. Five weeks after HCRT2-SAP administration a loss of HCRT-ir neurons into LH was produced. In normal animals, a high density of HCRT-ir fibers was found in the septum and was poor in the corpus callosum and striatum. These densities decreased in lesioned animals. To label dividing cells, we used 5-bromo-2′-deoxyuridine (BrdU). BrdU was injected twice daily during days 10-14 after lesion, saline or control procedure. Animals were killed at 3 weeks after the last BrdU injection. Experimental depletion of HCRT in rats increases precursor cell proliferation in the SVZ and subependimal layer of 3rd ventricle. However, we don’t find BrdU/HCRT double-labeled cells in the subependimal zone or LH. These observations suggest that the HCRT is a negative factor in adult neurogenesis.

Related Products: Orexin-B-SAP (Cat. #IT-20)

Ma J, Tai S, Leung LWS (2007) Ketamine-induced gating deficit of hippocampal auditory evoked potentials in rats is alleviated by medial septum inactivation and antipsychotic drugs. Neuroscience 2007 Abstracts 498.12/GG19. Society for Neuroscience, San Diego, CA.

Summary: Gating of sensory responses is impaired in schizophrenic patients and animal models of schizophrenia. Ketamine, an N-methyl-D-aspartate receptor antagonist, is known to induce schizophrenic-like symptoms in humans. In this study, we investigated some conditions underlying ketamine’s effect on the gating of auditory responses in the hippocampus of freely moving rats. Gating was measured by the ratio of the second-click response (P2) to the first-click response (P1), or P2/P1, with P1 and P2 measured as peak amplitudes. Ketamine (1, 3 or 6 mg/kg s.c.) dose- dependently increased P2/P1 ratio as compared to saline (s.c.). P2/P1 ratio in saline injected rats was 0.48 + 0.05 and was 0.73 + 0.17 in ketamine (3mg/kg) treated rats. Pre-inactivation of the medial septum with GABAA receptor agonist muscimol (0.25 μg/0.6 μL) or systemic administration of antipsychotic drugs, including chlorpromazine (5 mg/kg i.p.), haloperidol (1 mg/kg i.p.) or clozapine (7.5 mg/kg i.p.), decreased P2/P1 to values comparable to normal rats without drug injection. Infusion of muscimol in the medial septum or injection of antipsychotic drug alone did not affect the P2/P1 ratio. However, rats with selective lesion of the septohippocampal cholinergic neurons (by 192-IgG saporin) showed significant higher P2/P1 (0.86 + 0.10) than that of sham lesioned rats (0.26 + 0.07), but ketamine’s effect in increasing P2/P1 ratio was preserved. It is suggested that the septohippocampal cholinergic inputs participate in normal auditory gating in the hippocampus whereas the entire medial septum mediates ketamine-induced deficit of hippocampal auditory gating. In addition, the effectiveness of various antipsychotic drugs in antagonizing ketamine-induced impairment of auditory gating confirms the validity of this animal model of schizophrenia. (Supported by NSERC grant and CIHR grant 15685).

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

Li A-J, Dinh TT, Ritter S (2007) Destruction of NPY receptor expressing neurons in the arcuate nucleus causes obesity and hyperphagia without increasing lateral hypothalamic orexigenic peptide gene expression. Neuroscience 2007 Abstracts 524.20/BBB20. Society for Neuroscience, San Diego, CA.

Summary: NPY-SAP, a conjugate of neuropeptide Y (NPY) and the ribosomal inactivating toxin, saporin (SAP), is a compound that selectively lesions NPY receptor-expressing neurons. Previously we showed that injection of NPY-SAP into the hypothalamic arcuate nucleus (ARC) induces hyperphagia and obesity in rats. To further investigate the mechanisms responsible for NPY-SAP-induced obesity, we injected NPY-SAP or blank-saporin (B-SAP) control into the ARC and subsequently examined the expression of two orexigenic neuropeptide genes in the lateral hypothalamic area (LHA), which is densely innervated by ARC neurons. Our hypothesis was that loss of leptin-sensitive neurons in the ARC in the NPY-SAP injected rats would lead to increased expression of orexigenic neurons elsewhere in the hypothalamic feeding circuitry. Body weight gain and food intake were dramatically increased in the NPY-SAP group. In addition, expression of NPY and cocaine- and amphetamine-regulated transcript (CART) mRNA was significantly reduced in the ARC of obese rats, indicating a loss of NPY receptor-expressing NPY and CART neurons in this region. In contrast, NPY and CART gene expression in the dorsomedial hypothalamic nucleus was unchanged in NPY-SAP rats, indicating that the NPY-SAP-induced lesion was limited to the ARC. However, contrary to our hypothesis, expression of the orexigenic neuronpeptides, melanin-concentrating hormone (MCH) or prepro-orexin mRNA in LHA was not enhanced, but was slightly reduced in the NPY-SAP rats. These results indicate that an enhancement of MCH or orexin expression in the LHA is not necessary for the hyperphagia and obesity observed after NPY-SAP lesions in the ARC. Supported by PHS grant #DK 40498.

Related Products: NPY-SAP (Cat. #IT-28), Blank-SAP (Cat. #IT-21)

Haller J, Toth M, Zelena D, Halasz J (2007) Molecular basis of violent behavior: The role of NK1 receptors. Neuroscience 2007 Abstracts 531.22/GGG24. Society for Neuroscience, San Diego, CA.

Summary: Background. Neurons expressing Neurokinin1 receptor (NK1 or Substance P receptor) are abundant in limbic areas crucial for different emotional behaviors. In recent years, NK1 receptor blockers were proposed for the treatment of anxiety and depression. Moreover, in two different laboratory models, NK1 receptor blockade was successfully used to decrease violent components of aggression related behaviors in Wistar rats (Biol. Psychiatry, 2007, in press). In the above study, the NK1 receptor blockade reduced the number of more violent hard bites, while the number of soft bites was unaltered. Aggressive encounters were accompanied by a marked activation of neurons expressing NK1 receptors in the medial amygdala and in the hypothalamic attack area, where the highest number and proportion of activated NK1 positive neurons were found. Aim / Methods. We evaluated the precise role of neurons expressing NK1 receptors in the hypothalamic attack area during resident/intruder test. These neurons were selectively eliminated by a Substance P conjugated saporin bilateral microinjection into the hypothalamic attack area. After a week recovery, lesioned and vehicle treated control residents were faced with a smaller untreated opponent in their home cages for 20 min. The brains of the residents were later removed to assess the site of injection and the extent of the lesion. Results. In lesioned Wistars, the bilateral microinjection resulted in a complete and selective disruption of NK1 positive neurons in the hypothalamic attack area. Compared to vehicle injected controls, the number of hard bites toward unfamiliar residents showed a marked decrease (almost a complete abolition) in the lesioned group. The latency of hard bites was significantly increased compared to vehicle injected controls. The number of bite attacks was also reduced, but this reduction was mainly secondary to the dramatic reduction in the number of hard bites. Conclusions. Our data show that hypothalamic neurons expressing NK1 receptors are involved in the control of aggressiveness, especially in the expression of violent attacks. These data confirm and support earlier results that NK1 antagonists – beyond anxiety and depression – may also be useful in the treatment of aggressiveness and violence.

Related Products: SP-SAP (Cat. #IT-07)

Gaffan D, Baxter MG, Browning PGF (2007) Intact delayed nonmatching-to-sample in monkeys with combined lesions of the temporal cortical cholinergic system and the fornix. Neuroscience 2007 Abstracts 341.11. Society for Neuroscience, San Diego, CA.

Summary: Rhesus monkeys were pre-operatively trained in truly trial-unique delayed nonmatching-to-sample (DNMS) in an automated apparatus. They were then divided into a control group (n=3) and an experimental group (n=3) and received injections into the inferior temporal cortex of either saline (controls) or the selective cholinergic immunotoxin ME20.4-saporin (experimentals). A postoperative DNMS test showed no significant impairment in the experimental group, both groups performing at their pre-operative level. Both groups then underwent a second surgery to transect the fornix. Again, there was no significant impairment in DNMS, both groups performing at their pre-operative level. If the lesions are confirmed histologically then these results are in marked contrast to our findings with scene learning, in which monkeys with the same combined lesion as those in the present experimental group were severely impaired. However, a number of recent studies have shown that tasks with temporally complex events extended over trials, like DNMS, discrimination learning set, and serial reversal set, depend on a short-term prospective memory strategy that is supported by the interaction of temporal cortex with prefrontal cortex. Thus, the performance of DNMS does not require the laying down of new long-term memories.

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