GABAA ρ receptor mechanisms in the rat amygdala and its role in the modulation of fear and anxiety

Accumulating evidence for the presence of GABA(A) rho receptors within the amygdala which differ from other members of the GABA(A) receptor family in both subunit composition and functional properties has been recently obtained. This work was conducted to study whether GABA(A) rho receptors may have a putative role in the amygdaloid modulation of fear and anxiety. It was found that the bilateral intra-amygdaloid administration (6-240 pmol/side) of (1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid, a selective GABA(A) rho receptor antagonist, reduced dose-dependently the exploration of the open arms of the elevated plus-maze without affecting locomotion and increased the plasma levels of corticosterone. In contrast, bicuculline in the dose range used (1.8-60 pmol/side) induced seizures, but had no effects on the exploration of the maze. It is suggested that GABA(A) rho receptors may have a role in the amygdaloid modulation of fear and anxiety.