Envolvimento dos receptores muscarínicos na memória do contexto e da associação contexto-choque na tarefa do condicionamento do medo ao contexto

• Ano de defesa: 2009
• Autor(a) principal: Mazzeo, Ricardo Teixeira [UNIFESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo (UNIFESP)
• Palavras-chave em Português: Escopolamina; Memória espacial; Memória emocional; Aprendizado latente; Hipocampo; Scopolamine hydrobromide; Spatial memory; Emotional memory; Latent learning; Hippocampus
• Link de acesso: http://repositorio.unifesp.br/handle/11600/9460

The cholinergic system participates in the processes of acquisition and consolidation of contextual fear conditioning (CFC), the administration of muscarinic cholinergic antagonist affect both stages of CFC. However it is not clear whether muscarinic receptors are critical for the formation of a memory representation of the context or for the association of such representation with the foot-shock. Through the paradigm of the context pre-exposure facilitation effect, in which the learning about the context is separated from the learning about the context-shock association, the present study examined the effects of dicyclomine and scopolamine on the acquisition and consolidation of context representation and context-shock association. Male Wistar rats were used to verify the dicyclomine effects in the acquisition of CFC, for that it recived an intra-peritoneal injection before pre-exposure or before training. To verify the effects of scopolamine in acquisition and consolidation of CFC, the animals received an intra-hippocampal injection of saline or scopolamine before or after pre-exposure or training. The animals were pre-exposed to context A or B and trained and tested in the context A. The control group (saline-saline), that were pre-exposed to the same context of the training (context A), displayed more freezing time than those pre-exposed to a different context (context B). The treatment with both drugs before the training session impaired the conditioned freezing response of animals pre-exposed to the context A, but the treatment before the pre-exposure session had no effect on freezing response. The treatment with scopolamine after the pre-exposure session impaired performance of animals, but treatment after the training session had no effect on the response of animals. These results suggest that scopolamine and dicyclomine affect the acquisition of CFC, by impairing the learning about context-shock association or the evocation of context representation. Moreover, these drugs do not alter the acquisition of context representation. Treatment with scopolamine interferes with the consolidation of the context representation, without interfering with the consolidation of context-shock association.