Papel dos receptores 5-HT2 da amígdala e hipocampo na modulação da ansiedade em camundongos expostos ao labirinto em cruz elevado.

Abstract

It has been demonstrated that serotonin (5HT) plays a dual role on anxiety states. Depending on the type of 5HT receptor and cerebral sites serotonin increases or decreases anxiety. Several studies have emphasized a role of the 5HT2 receptors on anxiety modulation. In rats, intra-hippocampus or intra-amygdala infusions of 5HT2 receptor ligands result in inconsistent effects in many animal models of anxiety. This study investigated the effect of the 5HT2B/2C receptor agonist mCPP bilaterally microinjected into dorsal (DH: 0, 0.3, 1.0 or 3.0 nmol/0.2 µl) or ventral (VH: 0, 0.3, 1.0 or 3.0 nmol/0.2 µl) hippocampus and amygdaloid complex (0, 0.15, 0.5, 1.0 or 3.0 nmol/0.1 µl) in mice exposed to the elevated plus maze (EPM). Test sessions were videotaped and subsequently scored for conventional indices of anxiety (percentage of open arm entries and percentage of open arm time) and locomotor activity (closed arm entries). Results showed that mCPP microinfusions into DH or VH did not affect any behavioral measure in the EPM. However, when injected into the amygdaloid complex this 5HT2 receptor agonist selectively increased anxiety at 1 nmol dose. In addition, none dose of mCPP changed locomotor activity when injected into the amygdaloid complex. Our results suggest that the 5HT2B,2C receptors located within the amygdaloid complex (but not within the hippocampus) play a role on anxiety in mice exposed to the EPM.