sfn2004

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.

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

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.

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

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.

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

Bailey AL, Bennett G, Ribeiro-da-Silva A (2004) Investigation of the functional role of non-peptidergic primary afferent sensory fibres in the transmission of pain related information. Neuroscience 2004 Abstracts 484.1. Society for Neuroscience, San Diego, CA.

Summary: It is well established that small diameter, unmyelinated, primary afferent C-fibres can be divided into two neurochemically defined populations, one that contains neuropeptides such as Substance P (SP) and Calcitonin-gene related peptide (CGRP) and the other which binds Isolectin B4 (IB4) and is relatively peptide negative. A great deal of circumstantial evidence indicates that the non-peptidergic afferents play a functionally distinct role in pain transmission compared to peptidergic afferents. Indeed, the concept of two distinct subpopulations of C-fibres would indicate the occurrence of parallel processing in pain pathways. However, the functional role of non-peptidergic afferents in the transmission of pain-related information is still unclear. In an attempt to clarify their functional role, we decided to study the development of hyperalgesia and allodynia in adult male Sprague-Dawley rats with selective ablation of IB4-binding, non-peptidergic afferent input to the dorsal horn. To achieve this, we injected IB4 conjugated to Saporin (SAP) into the left sciatic nerve and examined both neurochemical and behavioural changes over a month’s time. Our data show that following injection of the toxin conjugate, IB4-labelling, P2X3-immunopositive fibre terminals disappear from a band in the superficial dorsal horn that expands over a two week period until it comprises most of the mediolateral extent of the dorsal horn. Behavioural data indicates that there are transient changes in acute pain thresholds to mechanical and thermal stimuli. Changes in pain thresholds in animals lacking non-peptidergic input into the spinal dorsal horn in an animal model of Complete Freund’s Adjuvant (CFA) induced inflammation will also be presented.

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McGaughy JA, Koene R, Eichenbaum HB, Hasselmo ME (2004) Effects of cholinergic deafferentation of prefrontal cortex on working memory: A convergence of behavioral and modeling results. Neuroscience 2004 Abstracts 551.7. Society for Neuroscience, San Diego, CA.

Summary: In humans, the prefrontal and medial temporal lobe areas are differentially activated during working memory dependent upon the whether stimuli are familiar or novel. Prefrontal activation occurs with highly familiar stimuli whereas the medial temporal lobe is activated by novel stimuli (Stern, et al. Hippocampus v. 11, 2001). The maintenance of novel information in the entorhinal cortex (EC) is hypothesized to depend upon self-sustained spiking activity in single neurons produced by cholinergic activation of muscarinic receptors (Klink and Alonso, J. Neurophys. 77, 1997). The current study investigated whether cholinergic modulation of the prefrontal cortex regulates sustained spiking activity for familiar stimuli. Rats were trained in an odor-cued delayed non-matching to sample task. After reaching asymptotic performance, rats were infused bilaterally with either 192 IgG-saporin (SAP) or its vehicle into the prefrontal cortex(PFC;0.01μg/μl;1.0μl/injection). Following PFC-SAP lesions,rats were impaired in working memory with highly familiar odors when choice stimuli were probed sequentially but not simultaneously. Though PFC-SAP rats reliably sampled both choices, they failed if the first cup probed matched the sample. PFC-SAP rats were also unable to maintain multiple items in memory. These impairments cannot be explained by the loss of response inhibition, the conditional response rule, attentional or sensory abilities. It is hypothesized that in the absence of a functional frontal cortex, the PFC-SAP rats relied on the EC. Computational modeling of EC suggests repetitions of an odor or the presentations of multiple odors disrupt the pattern of self-sustained spiking in this area and, thus, the representation of the stimulus. These data elucidate the interplay between the PFC and EC during a working memory task.

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

Stead S, Doering LC (2004) A novel mouse model for Parkinson’s disease using an immunotoxin directed at the dopamine transporter. Neuroscience 2004 Abstracts 563.1. Society for Neuroscience, San Diego, CA.

Summary: Current laboratory models of Parkinson’s disease utilize neurotoxins directed at midbrain dopamine neurons to mimic nigro-striatal dopaminergic neuron degeneration. To date, however, there is no single model that accurately simulates the pathogenic, histological, biochemical and clinical features relevant for the investigation of PD. The most common laboratory rodent model of Parkinson’s uses the neurotoxin 6-hydroxydopamine (6-OHDA) to cause relatively acute degeneration of the dopamine neurons in the substantia nigra (Schwarting RKW and Huston JP, 1996, Prog Neurobiol., 50:275-331). Axonally transported toxins can be used to make selective lesions in the central nervous system. We have found that a slower degeneration of the SN can be achieved with an immunotoxin directed against the dopamine transporter (DAT). This immunotoxin, consisting of the highly active ribosome inactivating protein Saporin linked to an antibody to the dopamine transporter, was recently reported to cause selective degeneration of the SN in rats (Wiley RG et al., 2003, Cell Mol Neurobiol., 23:839-850.). We have shown that unilateral stereotaxic injection of the Anti-DAT-Saporin into the striatum of female C57BL6 mice causes a progressive reduction in the numbers of DA neurons in the SN in comparison to the non-lesioned hemisphere, and sham controls. Furthermore, in parallel to the immunohistochemical dopamine neuron death, the animals display a pronounced circling behaviour when challenged with apomorphine (6mg/kg). This model is akin to the gradual 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.

Related Products: Anti-DAT-SAP (Cat. #IT-25)

Leung LS, Petropoulos S, Ma J, Shen B (2004) Cholinergic neurons in the basal forebrain participate in consciousness and general anesthesia. Neuroscience 2004 Abstracts 565.4. Society for Neuroscience, San Diego, CA.

Summary: Acetylcholine (Ach) in the brain has long been associated with consciousness. In this study, we assessed consciousness in rats by their EEG and behavioral responses to a general anesthetic. Cholinergic neurons in the nucleus basalis of Meynert (NbM) were lesioned by bilateral injection of toxin IgG192-saporin (0.15 μg at P1.4, L2.7, 7.7 mm below dura) in 10 adult male rats. Control (5 rats) had saline injected into the NbM. EEGs were recorded by electrodes placed in layer V of the frontal cortex (FC) and visual cortex (VC). Spectral analysis of the spontaneous EEGs in FC and VC during awake-immobility indicated that lesioned animals showed higher delta (0.8 to 4 Hz) and lower gamma (30- 58 Hz) power as compared to controls. Subsequent acetylcholinesterase staining (optical density) confirmed significant Ach depletion in both FC and VC, in the lesion as compared to the control group (P<0.002, Wilcoxon). When challenged with a normally subanesthetic dose of general anesthetic, the lesioned rats showed, as compared to controls, significantly longer durations of loss of righting and tail-pinch response after 5 mg/kg i.v. propofol (P<0.001), but not after 20 mg/kg i.p. pentobarbital or 2% halothane. In correspondence with the deep behavioral anesthesia, delta power at FC after propofol was significantly larger in lesioned than control rats. Lesioned rats, as compared to controls, also showed decreased locomotion (behavioral excitation) when given 2% halothane in a large chamber. In summary, a loss of Ach in the neocortex decreases the level of consciousness as indicated by increased delta and decreased gamma EEG, and by an increased sedative/ anesthetic response to propofol i.v. We suggest that patients with Alzheimer disease may show altered response to some general anesthetics.

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

Ohara PT (2004) Exercise accelerates relapsing paralysis after recovery from spinal demyelination. Neuroscience 2004 Abstracts 419.6. Society for Neuroscience, San Diego, CA.

Summary: Exercise has been used to improve motor performance in humans and animals following spinal cord injury. The effects of exercise are generally positive but it is not known whether exercise is universally beneficial, particularly in rat models of spinal injury. We examined the spinal cord morphology and motor function recovery for 18 months in rats that had undergone lumbar spinal demyelination induced by CTB-saporin. Following the initial demyelination and paraplegia, motor function recovered and was stable for up to nine months after which there occurred a slow deterioration of function that occurred earlier and was more severe in rats that had been exercised on a treadmill. Rats given treadmill exercise starting three weeks after toxin injection had a mean motor deficit score of 3.0 (i.e. paraplegia) at perfusion while the non-treadmill treated rats had a mean score of 1.8 (SD 0.38, n = 6, p<0.05). Histological examination showed the same morphological changes occurred in both exercise and non-exercise treated animals including the loss of motoneurons, loss of spinal white matter and appearance of large spheroids of calcium in the ventral and dorsal horns and occasionally in the white matter. These findings suggest that, in addition to the acute effects of the toxin induced demyelination from which there is recovery of motor function, there are chronic irreversible effects of the toxin, or the initial demyelination, that cause a slow progressive degeneration of the spinal cord. This model might therefore be useful to study the long term effects of spinal insult of the type associated with conditions such as post-polio syndrome.

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

Janczewski WA, McKay LC, Feldman JL (2004) Decreased number of sighs and post-sigh apneas indicates neuronal degeneration within the preBötzinger complex. Neuroscience 2004 Abstracts 424.10. Society for Neuroscience, San Diego, CA.

Summary: Sighs, also known as augmented or deep breaths, are inspiratory efforts of increased tidal volume, duration and biphasic shape. Sighs occur periodically in most mammals and are present throughout life, even in utero. Some sighs are followed by a post-sigh apnea lasting longer than 2 average respiratory periods. In adult rats, the number of sighs per hour [sigh index (SI)] is ~20. When we injected 0.2 pmol of substance P (SP) into the preBötzinger Complex, SI increased to >100, suggesting that activation of preBötzinger Complex NK1 receptor expressing (NK1R) neurons produces sighs. We hypothesized that degeneration of preBötzinger Complex NK1R neurons would decrease SI and eliminate post-sigh apneas. We injected the toxin saporin conjugated to SP bilaterally into the preBötzinger Complex to selectively destroy NK1R neurons. The number of ablated NK1R neurons increased from days 2-6 postinjection. In all rats at days 2-3, SI dropped below 5 and all post-sigh apneas were eliminated. In one group of rats (n=6), an ataxic breathing pattern developed, resulting from >90% NK1R cell loss. In these rats, all sighs were eliminated from days 3-4 postinjection. A second group of rats (n=5) maintained a eupneic breathing pattern. They were observed for two months postinjection and did not recover the preinjection sigh pattern. Their NK1R cell loss was <80% after two months, but must have been smaller at day 2 postinjection when their sigh pattern changed. We hypothesize that a modest (<< 80%) decrease in the number of NK1R neurons within the preBötzinger Complex, due to a toxin here but otherwise due to aging or neurodegenerative processes, may explain the decrease in SI seen with age in humans. We postulate that a marked decrease in the number of sighs and post-sigh apneas is an early symptom of neurodegeneration within the preBötzinger Complex.

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

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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