sfn2004

McKay LC, Janczewski WA, Feldman JL (2004) Ablation of NK1 receptor-expressing (NK1R) neurons within the preBötzinger complex (preBötC) in adult rats disrupts breathing during sleep before affecting breathing in wakefulness. Neuroscience 2004 Abstracts 424.9. Society for Neuroscience, San Diego, CA.

Summary: In adult rats, as the number of ablated preBÖtC NK1R neurons increases, eupnea is progressively disrupted during wakefulness, eventually resulting in an ataxic breathing pattern when cell loss is >80% (Gray et al. Nat. Neurosci. 2001). Is there a disruption of breathing during sleep prior to a disruption of breathing in wakefulness? Adult male Sprague Dawley rats (n=4) were instrumented to record: diaphragmatic, abdominal and neck EMG; ECG, and; EEG. Subsequently, the toxin Saporin conjugated to Substance P was injected bilaterally into the preBÖtC to selectively destroy NK1R neurons. Rats were monitored from day 1 postinjection until they were sacrificed between days 9-15. On days 3-4, changes in breathing pattern were observed during REM sleep. These changes were characterized by an increase in frequency of central apneas (4-7/hour vs 2/hour preinjection controls; p<0.05) and an increase in apnea length (3-6 sec vs 1-2 sec preinjection controls; p<0.05). On days 4-6, the onset of REM sleep typically induced hypopnea and a central apnea resulting in an arousal to wakefulness within 4-10 sec and the reestablishment of a normal breathing pattern. Eupnea was maintained during wakefulness; in some cases there was an increase in frequency compared to preinjection controls (183 vs 120 breaths/min). From day 6 onwards, breathing rhythm was progressively disrupted until an ataxic breathing pattern developed during wakefulness (~day 8). At this stage, rats were unable to sleep because breathing stopped upon sleep onset. In all cases, lesion extent at sacrifice, as determined by histology, was confined to the preBÖtC and >80% of NK1R neurons were destroyed. The spreading ablation of preBÖtC NK1R neurons results in a progressive disruption in breathing pattern, initially during sleep leading to pathological disturbances of breathing in both sleep and wakefulness.

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Banihashemi L, Rinaman L (2004) Noradrenergic inputs to the bed nucleus of the stria terminalis (BNST) contribute to yohimbine-induced activation of BNST neurons and hypothalamic CRH neurons in rats. Neuroscience 2004 Abstracts 426.10. Society for Neuroscience, San Diego, CA.

Summary: Noradrenergic (NA) inputs to the BNST and hypothalamus are implicated in behavioral and endocrine responses to stress and anxiety. Yohimbine (YO) increases transmitter release from NA terminals, which promotes anxiety and activates CRH neurons at the central apex of the HPA axis. We hypothesized that these effects require NA signaling within the BNST. To test this, saporin toxin conjugated to an antibody against dopamine beta hydroxylase (DSAP; 50-100 nl) was microinjected bilaterally into the BNST to eliminate its NA inputs in adult male Sprague-Dawley rats. After 2 weeks, DSAP-treated rats and intact control rats were injected with YO (0 or 5 mg/kg, i.p) and perfused with fixative 90 min later. Brain sections were processed to reveal DSAP lesion extent and YO-induced cFos activation. DSAP rats displayed nearly complete loss of NA terminals in the BNST, accompanied by moderate loss of hypothalamic NA terminals. Significantly fewer BNST neurons and hypothalamic CRH neurons were activated in DSAP rats after YO compared to activation in intact control rats, whereas parabrachial and central amygdala activation in DSAP rats was not diminished. We conclude that medullary NA neurons projecting to the lateral BNST collateralize to innervate the paraventricular hypothalamus, and that these NA projection neurons are necessary for YO to activate BNST and hypothalamic CRH neurons. Studies are ongoing to determine whether BNST-projecting NA neurons are necessary for YO to inhibit food intake or support conditioned flavor avoidance.

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Pizzo DP, Samadzadeh L, Thal LJ, Frielingsdorf H (2004) Impact of 192 IgG-saporin medial septum lesions on working memory. Neuroscience 2004 Abstracts 436.1. Society for Neuroscience, San Diego, CA.

Summary: It is generally believed that cholinergic input to the hippocampus (hpc) is involved in learning and memory. The objective of the present study was to clarify whether working memory as assessed by the Morris water maze (mwm) is impaired by selective lesions of the cholinergic cells in the medial septum in adult male rats using 75 ng192IgG-saporin per side. Two weeks post-lesion, naive and lesioned rats were trained in the mwm task focusing on working memory, which was tested using a new platform location every day. The difference (improvement) in latency between trial 1 and 2 was used as an index of working memory function. Nine different platform locations were tested. The locations yielding the highest group difference were retested, with increasing intertrial intervals (ITI) from 30 min to 24 h between the 1st and 2nd trial. In a majority of the trial blocks there was a trend suggesting that lesioned rats had impaired working memory, however there was no consistent significant difference between groups in any of the tasks. To potentially further separate the groups rats were then infused with nerve growth factor (NGF; 5 µg/day), or vehicle into the ventricular system. After 17 days of infusion working memory was retested, however NGF treatment did not affect performance. The lesions were complete as measured by loss of choline acetyltransferase activity (ChAT) to less than 10% of levels of the naive, vehicle treated rats. NGF infusion increased hpc ChAT activity in naive but not in lesioned rats. In conclusion, selectively reducing ChAT activity by more than 90% in the hpc is not sufficient to significantly impair working memory as assessed by the mwm. We cannot exclude that a more sensitive working memory task would reveal a deficit in the lesioned animals, however it is also possible that intact septohippocampal cholinergic projections are not crucial for working memory function.

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Corley SR, Atkinson M, Cabrera S, Castillo A, Crawford D, Kitto M, Butt AE (2004) Cholinergic basal forebrain lesions disrupt acquisition of cued and uncued differential reinforcement of low rate responding. Neuroscience 2004 Abstracts 436.10. Society for Neuroscience, San Diego, CA.

Summary: The frontal cortex, medial septum/vertical diagonal band (MS/VDB), and hippocampus have been implicated in supporting differential reinforcement of low rate responding (DRL) behavior in rats. Because the frontal cortex and hippocampus receive cholinergic input from the basal forebrain, we hypothesized that 192 IgG-saporin (SAP) lesions of the basal forebrain would disrupt DRL acquisition in the current experiment. To distinguish between potential deficits in timing, as opposed to impairments in response inhibition, we trained rats in either the standard DRL task (which requires both timing of behavior and response inhibition) and on a cued version of the task (which does not require the ability to time behavior but does require response inhibition). Rats were first shaped to bar press before receiving either bilateral SAP lesions of the basal forebrain or sham lesions. Rats were returned to bar press training for 5 more days. Rats were then shifted to a DRL 20 s, LH 10 s (limited-hold 10 s) schedule of reinforcement. Half of the rats were provided with a cue light signaling the availability of reinforcement, whereas the other half underwent standard DRL 20 s LH 10 s testing without the visual cue. Rats with basal forebrain lesions showed a transient impairment in response inhibition in both the standard and the cued version of the DRL task. Both lesion groups made more responses at short inter-response-intervals than controls across the first 15 test days, although this impairment attenuated by the 20th test day. These data suggest that the cholinergic basal forebrain is involved in learning to withhold responding during acquisition in DRL.

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Arshad S, Li P, Fitz NF, Johnson DA (2004) Effect of dehydroepiandrosterone sulfate on retention in passive avoidance in septal hippocampal cholinergic lesioned rats. Neuroscience 2004 Abstracts 436.11. Society for Neuroscience, San Diego, CA.

Summary: Infusions of 192 IgG-saporin (SAP) into the medial septum (MS) selectively destroys cholinergic neurons projecting to the hippocampus. Our previous study demonstrated that this lesion impairs retention but not acquisition of a passive avoidance (PA) task in rats. The present study determined whether the neurosteroid Dehydroepiandrosterone sulfate (DHEAS) (0, 1, 3, 10, 30 mg/ml) could reverse SAP induced impairments of PA retention. Male Sprague-Dawley rats were administered either SAP (.22μg/μl) or vehicle directly into the MS. Passive Avoidance training began 2 weeks later. Training consisted of placing the animal into the lighted chamber of the apparatus and then delivering a foot shock (.75mA, 1 sec), when the animal moved into the adjacent darkened chamber. Training was repeated until the animal avoided the dark chamber for 2 consecutive trials of 2 minutes duration. Retention (latency to crossover to the dark chamber) was tested after seven days. DHEAS was administered one hour prior to retention testing. Results showed a dose dependent increase in crossover latency in SAP treated animals. DHEAS treatment in control animals, however, resulted in a dose dependent decrease in crossover latency. Thus, DHEAS attenuated the impairment in retention in SAP treated animals with hippocampal cholinergic hypofunction, but impaired retention in cholinergically intact rats in PA.

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

Fitz NF, Li P, Johnson DA (2004) Effects of dehydroepiandrosterone sulfate on delayed match to position T-maze task performance in 192- IgG saporin lesioned rats. Neuroscience 2004 Abstracts 436.2. Society for Neuroscience, San Diego, CA.

Summary: Prior studies have shown that infusion of 192 IgG-saporin (SAP), a cholinergic neurotoxin, into the media septum (MS) of rats selectively lesions cholinergic neurons that project to the hippocampus, resulting in impaired acquisition of a delayed matching to position (DMP) T-maze task. Since the neurosteriod dehydroepiandrosterone sulfate (DHEAS), displayed memory enhancing properties in rodents, the present study investigated the effects of DHEAS administration on MS SAP lesioned animals. Male Sprague-Dawley rats received intraseptal infusions of either cerebrospinal fluid or SAP (0.22 μg/μl). Fourteen days later, the rats were administered IP injections of either DHEAS (20mg/ml) or vehicle one hour prior to DMP testing. During the acquisition phase of testing, each rat completed 8 trial pairs per day until reaching criterion (15 of 16 correct choices). Treatment with DHEAS resulted in a 10% shortening of the number of days to reach criterion in the SAP treated animals compared to SAP non-treated animals.

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

Fletcher BR, Guzowski JF, Baxter MG, Shapiro ML, Rapp PR (2004) Hippocampal Arc and Homer 1a expression in behaviorally characterized 192 IgG-saporin lesioned rats. Neuroscience 2004 Abstracts 436.4. Society for Neuroscience, San Diego, CA.

Summary: Fornix lesions impair hippocampal dependent learning and block behavioral induction of the immediate-early gene Arc. The present experiment tested the role of cholinergic innervation in the transcriptional induction of the activity related immediate-early genes Arc and Homer 1a. 192 IgG-saporin or vehicle was injected into the medial septal nucleus and vertical diagonal band. Behavioral characterization on cued and spatial delayed match-to-place tasks in a radial arm water maze revealed an impairment in cognitive flexibility, but not spatial memory in lesioned animals. Immediately after animals explored two novel environments their brains were processed for fluorescence in situ hybridization with probes for Arc and Homer 1a to reveal the recent activation history of individual neurons. Confocal stereological quantification of labeling in the CA1 and CA3 cell fields of the hippocampus revealed no dramatic difference in number of positive cells between groups. These results show that, unlike fornix lesions, cholinergic denervation of the hippocampus is not sufficient to block behavioral activation of Arc or Homer 1a transcription. Therefore, cholinergic innervation is not required for Arc or Homer 1a expression.

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

Kitto MR, Carbrera S, Corley S, Castillo A, Atkinson M, Andrews C, Casteneda M, Crawford D, Iliscupidez M, Monahan R, Rodriguez D, Salley T, Butt AE (2004) 192 IgG-saporin lesions of the nucleus basalis magnocellularis impair biconditional discrimination learning in rats. Neuroscience 2004 Abstracts 436.5. Society for Neuroscience, San Diego, CA.

Summary: Previous results from our laboratory suggest that the cholinergic nucleus basalis magnocellularis (NBM) is involved in configural association learning but not in simple association learning. In the current experiment, we hypothesized that 192 IgG-saporin lesions of the NBM in rats would impair biconditional visual discrimination learning, which requires configural association learning. In contrast, we hypothesized that NBM lesions would not impair acquisition of a simple visual discrimination, which requires only simple association learning. In Problem 1, rats were trained in a T-maze to solve a simple visual discrimination between a food-reinforced black goal arm (B+) and a non-reinforced white arm (W-), where the start arm of the maze was always striped (S). Next, in Problem 2, the reinforcement contingencies of the goal arms were reversed (W+ vs. B-), and the start arm visual cue was changed to gray (G). Finally, rats underwent biconditional discrimination training where half of the trials were of Problem 1 type and half were of Problem 2 type. Separately, Problems 1 (S: B+ vs W-) and 2 (G: W+ vs B-) can be solved using simple associations. However, in the biconditional discrimination, where Problems 1 and 2 are intermixed, configural association learning is required. Preliminary results supported our hypotheses. Acquisition of Problems 1 and 2, the simple association problems, did not differ between the NBM lesion group and the control group. However, performance in biconditional discrimination was impaired in the NBM lesion group compared to controls. These results are consistent with the argument that the NBM is involved in configural but not simple association learning.

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Ricceri L, Scattoni ML, Cutuli D, Calamandrei G (2004) Effects of neonatal cholinergic lesions on fear conditioning in 18-day-old rats. Neuroscience 2004 Abstracts 436.9. Society for Neuroscience, San Diego, CA.

Summary: We have previously shown that neonatal intracerebroventricular (icv) injections of the selective cholinergic immunotoxin 192 IgG-saporin on postnatal day (pnd) 7 induces behavioural alterations already detectable in the third postnatal week. In the present study we injected 192 IgG-saporin icv, in the nucleus basalis magnocellularis (nbm) or in the medial septum (ms) in 7-day-old rats and we then analysed fear conditioning on pnd 18. Fear conditioning to both auditory cue and environmental context was evident in both control and lesioned rats on pnd 18. However, conditioning to the environmental context (measured by freezing duration) was significantly more marked in icv and MS lesioned rats, whereas no effect of the cholinergic lesion was evident on conditioning to the auditory cue. These results suggest that neonatal removal of the cholinergic input to the hippocampal region paradoxically facilitates processing of spatial information in young rats.

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Benassi SK, Blanco MM, Mello LE (2004) Electrophysiological profile of IgG192saporin-lesioned rats in the pilocarpine model of epilepsy. Neuroscience 2004 Abstracts 452.14. Society for Neuroscience, San Diego, CA.

Summary: In order to investigate the importance of the basal forebrain cholinergic reorganization to the epileptogenesis process, adult male Wistar EPM-1 rats (180-220g) were subjected to status epilepticus (SE) induction by pilocarpine injection (320mg/kg, i.p.), after cholinergic lesion through IgG192-saporin (5μg/5μL, i.c.v.). Two months after SE induction animals were deeply anesthetized (choral hydrate 400 mg/kg, i.p.) and subjected to the electrical stimulation of the right CA3 and recorded (3M NaCl, 1MΩ) in the contralateral (left) CA1 region. Histological analysis included Nissl staining for the location of stimulating and recording electrodes and histochemistry for acetylcholinesterase (AChE) for the assessment of IgG192-induced lesions. The administration of the IgG192-saporin consistently and specifically diminished AChE staining in the hippocampus and neocortex while not affecting other brain areas (e.g., amygdala, striatum, etc). As compared to naive control animals, pilocarpine-treated animals generally showed loss of paired-pulse inhibition and the presence of multiple population spikes. Epileptic animals that were pre-treated with the cholinergic toxin did not differ from untreated epileptic animals in terms of paired-pulse inhibition or the presence of multiple population spikes. Large paired-pulse facilitation (P2>10 P1) for interstimulus intervals varying from 20 to 200 ms was encountered for both groups of epileptic animals with no distinction between each other. We suggest that the basal forebrain cholinergic system does not have a major role in defining the hyperexcitability of hippocampal circuits in the pilocarpine model of epilepsy.

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