Investigação do papel dos receptores 5-HT3 da substância cinzenta periaquedutal dorsal na modulação dos comportamentos relativos à ansiedade no labirinto em cruz elevado e no campo aberto em ratos

Abstract

Anxiety is an emotional state characterized by physiological and psychological changes that provide an unpleasant feeling to the individual. However this behavior has great adaptive value, since it alerts the individual about possible dangers that particular situation can offer. It has been identified various brain regions related to neural substrate of anxiety and, among them, it is the periaqueductal gray matter (PAG). Several studies have demonstrated the involvement of serotonergic system of the dorsal portion of PAG (DPAG) in the modulation of behaviors related to anxiety. In view of this, the objective of this study was to evaluate the role of 5-HT3 receptors of the DPAG in the modulation of behaviors related to anxiety and locomotion in rats tested in the elevated plus maze (EPM) and open field (OF). Wistar rats received microinjection of 5-HT3 receptor antagonist dolasetron (100ng, 500ng and 1000ng) (experiment 1), 5-HT3 receptor agonist m-Chlorophenylbiguanide (mCPBG) (2,5μg, 5μg and 10mg) (Experiment 2) or saline 0.9% in the DPAG. After 10 minutes (experiment 1) or 5 minutes (Experiment 2), the rats were placed in the EPM and their performances were evaluated during 5 minutes. Twenty-four hours later the animals received the same doses that were microinjected on the previous day in the DPAG and after 10 minutes (experiment 1) or 5 minutes (experiment 2) were placed in OF and their behaviors were assessed for 15 minutes. In experiment 1 microinjection of dolasetron did not change the parameters of anxiety and locomotion in EPM and OF. In the experiment 2, the mCPBG at doses of 5μg and 10mg produced anxiolytic effect in EPM without changes in locomotor behavior. These results suggest that activation of 5-HT3 receptors in the SCPD eliciate an anxiolytic effect in rats evaluated in EPM.