Mechanisms of somatostatin-evoked responses in neurons of the rat lateral amygdala

The effects of somatostatin in the rat lateral amygdala (LA) in vitro were investigated through whole cell recording techniques. Somatostatin induced an inwardly rectifying K+ current in approximately 98% of LA projection neurons. Half-maximal effects were obtained by 189 nm somatostatin. The effects of somatostatin were insensitive to tetrodotoxin, reduced by Ba2+, occluded or abolished by the presence of nonhydrolysable GTP or GDP analogues, respectively, and blocked or mimicked by a somatostatin receptor type 2 antagonist (BIM-23627) or somatostatin receptor type 2 agonist (L-779,976), respectively, while somatostatin receptor type 1, 3 and 4 agonists were ineffective (L-797,591, L-796,778, L-803,087). Responses to somatostatin were associated with membrane hyperpolarization and decrease in input resistance, resulting in a dampening of cell excitability. It is suggested that these cellular mechanisms contribute to the role of somatostatin in decreasing anxiety behaviour as well as to anticonvulsant and antiepileptogenic actions of somatostatin or somatostatin agonists in the amygdala.