5-HT denervation of the adult rat prefrontal cortex induces changes in the expression of α4 and α7 nicotinic acetylcholine receptor subtypes

Introduction: Nicotinic acetylcholine receptors (nAChRs) are widely expressed throughout several brain regions. Formation of the alpha 4 beta 2 and alpha 7 subtypes in particular is involved in the organisation of different types of memory. Furthermore, due to their location, these receptors can control the release of various types of neurotransmitters and contribute to synaptic plasticity. Methods: Rats were divided into three groups, an experimental group (E), a sham-operated group, (S) and an intact group (T). In group E, stereotactic guidance was used to induce a chemical lesion with 1 mu/mu L of 5,7-dihydroxytryptamine (5,7-DHT) in the anteroventral part of the dorsal raphe nucleus (DRN). In the sham-operated group (5), animals underwent surgery including delivery of the same excipient solution to the same site. The intact group (T) received no treatment whatsoever. Twenty days after surgery, animals in all groups were euthanised by decapitation to evaluate the expression of alpha 4 and alpha 7 nAChRs by means of molecular biology techniques. Results: 5-HT denervation of the rat PFC differentially modified the expression of alpha 4 and alpha 7 receptors: while alpha 4 receptor expression increased, alpha 7 expression decreased. Conclusion: Expression differences observed between the two subtypes may be due to their separate locations. The alpha 4 subtype is found in postsynaptic locations and may be related to adaptive changes in postsynaptic cells, while the location of alpha 7 is presynaptic. This explains why the lesion and the elimination of 5-HT fibres in the CPF would cause a decrease in alpha 7 expression. (C) 2012 Sociedad Espanola de Neurologia. Published by Elsevier Espana, S.L. All rights reserved.