Laplante FP, Dufresne M, Lappi DA, Sullivan RM (2008) Depletion of cholinergic neurons in the nucleus accumbens and its possible involvement in schizophrenic symptomatology. Neuroscience 2008 Abstracts 761.18/FF34. Society for Neuroscience, Washington, DC.
Summary: Schizophrenia is a mental disorder characterized by dysfunctions in several neurotransmitter systems including the central cholinergic system. While alterations in cholinergic neurotransmission have been demonstrated in schizophrenic brains, their biological significance remains to be established. Post-mortem studies of schizophrenic patients have shown a reduction in the density of cholinergic interneurons in the striatum, most prominently in the ventral striatum or nucleus accumbens (N. Acc). Intra-accumbens acetylcholine interacts functionally with the mesolimbic dopaminergic system and is believed to dampen the effects of excessive dopamine (DA) release. Therefore, we hypothesize that a reduction in the density of cholinergic neurons in the N. Acc will be behaviorally relevant, if not causal, to the enhanced (ventral) striatal dopaminergic neurotransmission described in schizophrenia and may contribute substantially to the emergence of schizophrenic symptomatology. In this study we aimed to reproduce in rats a selective reduction in N.Acc. cholinergic cell density, and study the neurophysiological and behavioural consequences of these lesions, relevant to the neuropsychopathology of schizophrenia. A novel saporin immunotoxin coupled with an antibody targeting choline acetyltransferase (ChAT) has been developed. We microinjected this immunotoxin bilaterally (0.5 μg/μl; 0.5 μl) into the N. Acc (core and shell) of adult male Srpague-Dawley rats. Using immunohistochemistry to quantify ChAT staining, we have confirmed that this toxin caused a 40-50 % loss in the number of cholinergic neurons in this region within two weeks post-injection. Lesioned rats exhibited significantly higher spontaneous locomotor activity than control rats and were shown to be hypersensitive to the locomotor activating effects of amphetamine and quinpirole. Furthermore, in separate groups of animals, we have observed in lesioned rats, a reduction in the prepulse inhibition of the acoustic startle response. Taken together, it is proposed that reduction of cholinergic neurons in the N. Acc triggers an enhanced DA responsivity in the N.Acc which may prove highly effective in reproducing behavioral abnormalities analogous to those found in schizophrenia. The neurophysiological consequences of these lesions on DA neurotransmission will be further addressed by measuring both pre- and postsynaptic indices of DA function in this region.
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