References

Young D, Howe WM, Martinez V, Bruno JP, Sarter M (2007) Neuronal mechanisms underlying the cognitive symptoms in a model of schizophrenia: prefrontal cholinergic inputs are necessary for attentional performance following repeated exposure to amphetamine. Neuroscience 2007 Abstracts 606.9/GG1. Society for Neuroscience, San Diego, CA.

Summary: The neuronal and cognitive effects of repeated exposure to amphetamine (AMPH) model important aspects of schizophrenia. Our prior results indicated that the attentional performance of AMPH-pretreated animals was maintained by abnormally high levels of prefrontal acetylcholine (ACh) release, and that the disruption of attentional performance by AMPH challenges was associated with a failure of the prefrontal cholinergic input system to respond to task onset (Kozak et al. 2007). The present experiment was designed to demonstrate that prefrontal cholinergic inputs are necessary for the (residual) attentional performance following repeated AMPH exposure. As removal of cortical cholinergic inputs per se disrupts attentional performance, we tested the hypothesis that limited prefrontal cholinergic deafferentation, which does not affect baseline attentional performance, prevents the establishment of normal performance following AMPH pretreatment. Rats were trained to perform a sustained attention task requiring the detection of visual signals and the discrimination between signal and non-signal events. Bilateral infusions of small concentrations and volumes of the immunotoxin 192 IgG-saporin into the medial prefrontal cortex did not affect the animals’ baseline performance. After re-establishing stable baseline performance, animals were pretreated with either saline or AMPH in accordance with an established, non-neurotoxic, escalating dosing regimen (1-10 mg/kg, twice daily over 40 days; Robinson et al. 1988). Animals were tested daily throughout the experiment. Following completion of the pretreatment regimen, the attentional performance of sham-lesioned controls recovered slowly over three weeks of continued training/testing. In contrast, performance recovery of deafferented, AMPH-pretreated animals was robustly attenuated and failed to reach pre-treatment levels. Collectively, these results indicate the necessary role of the prefrontal cholinergic input system in mediating the residual attentional performance of repeated AMPH. Therefore, pro-cholinergic treatments are predicted to benefit the attentional performance of schizophrenics. Repeated AMPH serves as a useful model to investigate the neuronal mechanisms underlying the cognitive symptoms of schizophrenia.

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Ganapini V, Powers F, Kuper K, Taylor A, Fraley GS (2007) Galanin-like peptide stimulates feeding and sexual behavior via dopaminergic fibers within the medial preoptic area of adult male rats. Neuroscience 2007 Abstracts 626.14/VV17. Society for Neuroscience, San Diego, CA.

Summary: Galanin-like peptide (GALP) is a hypothalamic neuropeptide known to regulate both food intake and sexual behaviors in adult male rats. We have demonstrated that ICV GALP administration elicits a significant fos response within the mPOA; thus, we feel that GALP stimulates feeding and reproduction by actions within the mPOA. Recent data from our and other labs have led us to suspect that GALP effects on these behaviors are due to activation of tuberoinfundibular dopaminergic neurons that terminate within the mPOA. To test the hypothesis that GALP activates mPOA dopaminergic systems, we utilized an immunolesion technique to eliminate dopaminergic fiber input specific to the mPOA via a dopamine-transporter specific toxin (DATSAP, n = 8) and compared to control injections (SAP, n = 8). All animals were sexually experienced adult male Long Evans rats. We first tested their response to a sexually-primed female rat. DATSAP-treated male rats showed a significant (p <0.001) reduction in male sexual behavior compared to SAP controls. We found that elimination of dopamine fibers within the mPOA significantly (p < 0.001) eliminated all aspects of male sexual behavior under normal mating paradigms. Injections of GALP (5.0 nmol) significantly increased (p < 0.01) male sex behavior in SAP control male rats but GALP was unable to stimulate the expression of these behaviors in DATSAP-treated rats. ICV GALP significantly (p < 0.05) stimulated fos within the mPOA of SAP rats but not in DATSAP-treated male rats. There was no significant difference in 24 hr food intake between SAP and DATSAP rats. However, the orexigenic effect of ICV GALP was significantly (p < 0.001) attenuated in DATSAP-treated male rats compared to SAP controls. These data suggest that GALP activates feeding and sexual behaviors in male rats by stimulating dopaminergic neurons that terminate within the mPOA.

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I’Anson H, Jethwa PH, Tanna GA, Pattinson LM, Ebling FJP (2007) Histaminergic regulation of energy homeostasis in the Siberian hamster. Neuroscience 2007 Abstracts 629.17/YY20. Society for Neuroscience, San Diego, CA.

Summary: We tested the hypothesis that posterior hypothalamic histaminergic (HA) activity regulates energy homeostasis in the Siberian hamster during long day (breeding season) photoperiods. Adult male Siberian hamsters were given bilateral injections of the retrogradely transported ribosomal toxin, saporin, conjugated to orexin-B receptor antibody (OXSAP, 200 nl, 92 ng/ul) into the posterior hypothalamus (PH) to selectively destroy HA neurons, the majority of which possess orexin-B receptors. Controls were injected with unconjugated saporin (sham). Metabolic rate (VO2 ml/kg0.75/h), ingestive behavior and locomotor activity were monitored using the comprehensive lab animal monitoring system (CLAMS, Columbus instruments). Body weight was significantly decreased by day 12 post-surgery in OXSAP compared with sham hamsters and remained significantly lower throughout the 5 month study, even though food intake was comparable between groups. At 3 months post-surgery, OXSAP food intake was significantly higher in the dark (p< 0.05) and significantly lower in the light phase (p<0.05), but not different overall between groups. In addition, the frequency of feeding bout tended to be lower during dark and light phases compared with sham hamsters (p=0.07). Lower body weight with no overall change in food intake suggests an increase in energy expenditure in the OXSAP hamsters. Consistent with this interpretation, locomotor activity in OXSAP hamsters tended to be higher during the dark phase (p=0.09), but not in the light phase. In addition, metabolic rate was significantly higher during the first two hours of the dark phase compared with sham hamsters (p<0.05), and tended to be higher during the entire dark phase (p=0.08). During a second CLAMS study (4 months post-surgery), metabolic rate was monitored following injection of an H3 receptor antagonist (thioperamide, 30 mg/kg, ip) as a probe to determine if any significant HA cell loss had occurred. Metabolic rate was significantly lower during the first 2 hours after thioperamide in sham hamsters, but not in OXSAP hamsters, suggesting that HA regulation of energy balance had been compromised by the OXSAP lesion. Immunohistochemical results confirmed 63-96% loss of HDC-immunoreactivity in magnocellular neurons of the posterior hypothalamus in the OXSAP group. These data support the hypothesis that posterior hypothalamic HA neuron activity modulates metabolic activity during the breeding season in the Siberian hamster, although it is likely that ablation of additional neuronal phenotypes which express orexin-B (e.g. MCH) may contribute to the observed metabolic effects.

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Winter SS, Martin MM, Wallace DG (2007) Walking the Plank: Role of the medial septum in distance estimation. Neuroscience 2007 Abstracts 743.21/BBB15. Society for Neuroscience, San Diego, CA.

Summary: Controversy surrounds the role of the septohippocampal system in spatial orientation. Recent work has demonstrated that selective cholinergic deafferentation of the hippocampus impairs use of self-movement cues while sparing environmental cue use. Self-movement cues are generated from changes in position or direction. The current study examines the role of the septohippocampal cholinergic system in processing of self-movement cues related to changes in position or distance estimation in a food hoarding task. The probability of food hoarding has been shown to be influenced by travel distance and time to consume the food item. Long Evans female rats received either injections of 192 IgG-Saporin (SAP) or saline (SHAM) into the medial septum. Subsequent to recovery, rats were placed in a refuge on a 15 cm wide plank and allowed to traverse the plank to collect food pellets located at the end. Both the distance to the food pellet (2.4 vs. 4.8 m) and size of the food pellet (190, 500, 1000 mg) were varied across days. Differences in food hoarding probability were observed between groups. SAP rats were less likely to modify their food hoarding probability in response to changes in plank length relative to SHAM rats. These results are consistent with selective hippocampal cholinergic deafferentation producing deficits in processing self-movement cues related to distance estimation.

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

King M, Jentsch JD (2007) Prefrontal cortical norepinephrine depletion does not impair spatial working memory in rats. Neuroscience 2007 Abstracts 645.16/CCC18. Society for Neuroscience, San Diego, CA.

Summary: The midbrain dopamine neurons are thought to encode a reward prediction error signal (Schultz et al., 1997; Bayer & Glimcher, 2005). Parkinson’s disease (PD) is characterized by a loss of nigral dopamine neurons. Dopaminergic drugs including the dopamine precursor L-Dopa and D2 receptor agonists are taken to relieve disease symptoms. We hypothesized that patients with moderate PD (1) show atypical reinforcement learning off dopaminergic medication due to dopamine neuron loss, and (2) show more normal reinforcement learning on dopaminergic drug therapy. We developed a method to rapidly assess reinforcement learning in human subjects (Rutledge et al., SfN 2005) adapted from matching law tasks used in monkeys (Sugrue et al., 2004; Lau & Glimcher, 2005). On each trial, subjects choose one of two animated crab traps. Rewards (crabs worth $0.10) were scheduled for the two targets with different independent rates. Scheduled rewards remained available until the associated target was chosen, as in the original matching law experiments (Herrnstein, 1961). After a 5-minute training period, subjects completed 800 trials as we varied reward probabilities across blocks. PD patients (n=19) completed one session on and one off dopaminergic medication. Age-matched controls (n=21) and healthy young subjects (n=20) completed one session. We found that young and elderly control subjects had similar reinforcement learning rates, but learning rates were reduced in PD patients (when tested off medication). Learning rates in the same PD patients were restored to control levels when dopaminergic drugs were administered. We also found that the reinforcement-independent strategies of our subjects were influenced by dopamine. Young subjects tended to alternate targets independent of reward history. In contrast, elderly subjects (who suffer some dopamine neuron loss) had a tendency to perseverate in their choices. This tendency was increased in PD patients (off medication), but restored to control levels when dopaminergic drugs were administered. This effect on choice is not explained by existing models of dopamine function. These data support a role for dopamine in human reinforcement learning. Future models of decision making in reinforcement learning tasks must also account for a reward-independent effect of dopamine on choice behavior.

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

Nguyen WT, Buhalog A, Hendrickson M, Kalil RE (2007) On the survival of nestin-expressing neurons in the cholinergic basal forebrain after an immunolesion with 192-IgG-saporin. Neuroscience 2007 Abstracts 674.5/D24. Society for Neuroscience, San Diego, CA.

Summary: Nestin is a class VI intermediate filament protein that is widely accepted as a marker for uncommitted neural progenitor cells. However, we have described a class of cells in the cholinergic basal forebrain of the adult rat and human that express markers associated exclusively with neurons, e.g., NeuN, β-III tubulin, and choline acetyl transferase (ChAT) and also express nestin. We have termed these cells nestin-expressing neurons (NENs). To explore the possibility that the expression of nestin by NENs might provide a neuroprotective effect, we administered the immunotoxin 192-IgG-saporin (192-saporin). The toxin consists of a ribosome-inactivating protein coupled to a monoclonal antibody directed against the p75 nerve growth factor receptor (p75 NGFr). As a result, 192-saporin selectively destroys cells expressing this receptor, such as most of the cholinergic neurons in the basal forebrain. Two micrograms of 192-saporin in 6 µL of saline were injected unilaterally into the lateral ventricle of the brain in each of four adult Sprague-Dawley rats. Following a six day survival period, the rats were deeply anesthetized, perfused with 4% paraformaldehyde, and the brains were sectioned and immunostained for nestin and ChAT. After confirming that NENs, which were identified by the co-expression of nestin and ChAT, express the p75 NGFr, we determined the number of NENs in the medial septum and in the nucleus of the diagonal band as a percentage of all ChAT-positive neurons in these nuclei in rats treated with 192-saporin and in controls. We found no statistically significant difference in the proportion of NENs between rats that had received 192-saporin and controls. This result indicates that for the dose of 192-saporin and survival period used in these experiments, the expression of nestin does not confer a neuroprotective effect. Experiments using lower doses of 192-saporin and shorter survival times are underway.

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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.

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Burk JA, Altemose KE, Lowder MW (2007) Effects of spatial cueing on visual discrimination performance of rats following loss of basal forebrain corticopetal cholinergic neurons. Neuroscience 2007 Abstracts 424.4/HHH3. Society for Neuroscience, San Diego, CA.

Summary: Basal forebrain corticopetal cholinergic neurons are necessary for normal attentional performance. However, the exact attentional task parameters that are sufficient for inducing deficits following loss of basal forebrain corticopetal cholinergic neurons remain unclear. In Experiment 1, rats were trained to perform a spatially cued visual discrimination task (press a lever under an illuminated panel light) with explicit attentional demands removed. Animals then received infusions of the cholinergic immunotoxin, 192IgG-saporin, or saline into the basal forebrain. All animals were then tested in the same task trained before surgery and then task parameters, including the duration of visual signals and the inter-trial interval, were manipulated in order to tax attentional processing. Lesioned animals exhibited an initial increase in response latencies immediately following surgery but this deficit was not observed when task demands were increased. When the task was modified to remove spatial cueing, by presenting visual signals or no signal from a centrally-located panel light, lesioned animals exhibited an increase in lever press latencies compared to sham-lesioned animals. In Experiment 2, rats were trained in a visual discrimination task that, within each session, had blocks of trials with or without spatial cueing, using procedures similar to Experiment 1. After receiving intra-basalis infusions of 192IgG-saporin or saline, animals were tested for 12 sessions in the same task trained before surgery followed by one session in which the inter-trial interval was decreased. Lesioned animals did not exhibit deficits immediately following surgery, but did show elevated lever press latencies compared to sham-lesioned animals when the inter-trial interval was decreased. There was a trend for this lesioned-induced deficit to be more pronounced when spatial cues were not present. These experiments indicate that cortical acetylcholine is critical for maintaining normal visual discrimination performance when spatial cueing is not available. We speculate that, under conditions in which spatial cueing is unavailable, the lesion-induced increased lever press latencies reflect a disruption in recalling rules for an appropriate response.

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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.

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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.

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