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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

5-HT2 receptor mechanisms of the dorsal periaqueductal gray in the conditioned and unconditioned fear in rats

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Autor(es):
Oliveira, Luciana Chrystine ; Broiz, Ana Carolina ; Macedo, Carlos Eduardo de ; Landeira-Fernandez, J. ; Brandão, Marcus Lira [5]
Número total de Autores: 5
Tipo de documento: Artigo Científico
Fonte: Psychopharmacology; v. 191, n. 2, p. 253-262, Apr. 2007.
Área do conhecimento: Ciências Biológicas - Fisiologia
Assunto(s):Sistema nervoso central   Substância cinzenta periaquedutal   Receptores de serotonina   Ketanserina   Estados emocionais   Medo
Resumo

It is well known that 5-HT2 mechanisms modulate the defensive behavior produced by the stimulation of the dorsal periaqueductal gray (dPAG). However, in spite of the notion that past stressful experiences play a role in certain types of anxiety, only studies with the stimulation of the dPAG of rats without previous aversive experience have been conducted so far. We investigated the mediation of 5-HT2 receptors of the dPAG in rats previously submitted to contextual fear conditioning (CFC). Defensive behaviors induced by the activation of the dPAG were assessed by measuring the lowest intensity of electric current applied to this structure (threshold) able to produce freezing and escape responses during the testing sessions of CFC in which animals were placed in a context previously paired to footshocks. The 5-HT2 function of the dPAG in this condition was evaluated by local injections of ALPHA-methyl-5-HT (20 nmol/0.2 ul) and ketanserin (5 and 10 nmol/0.2 ul), selective agonist and antagonist of 5-HT2 receptors, respectively. In accordance with previous studies, ALPHA-methyl-5-HT increased the aversive thresholds (antiaversive effects) in naive rats, and injection of ketanserin into the dPAG did not produce significant effects. On the other hand, ketanserin decreased in a dose-dependent manner the freezing threshold (proaversive effect) determined by the dPAG electrical stimulation, whereas ALPHA-methyl-5-HT continued to show antiaversive effects in animals under CFC. The present results suggest that past stressful experience can produce changes in the synaptic function of 5-HT2 receptors within the dPAG with important impact on the expression of defensive behaviors. (AU)

Processo FAPESP: 02/03705-0 - Neurobiologia do medo e do stress
Beneficiário:Marcus Lira Brandão
Linha de fomento: Auxílio à Pesquisa - Temático