Inhibition of neurons in the rat medial amygdaloid nucleus in vitro by somatostatin.

Effects of somatostatin (SRIF) on neurons in the medial amygdaloid nucleus were investigated in rat brain slice preparations, using extracellular recordings. Following bath application of SRIF at 10(-7) - 10(-6) M, 63 of 81 (78%) medial amygdala neurons showed an inhibitory response. The inhibitory effect of SRIF was dose dependent, and the threshold concentration was approximately 10(-9) M. The inhibitory response to SRIF persisted during synaptic blockade in two-thirds of neurons tested. The inhibitory effect of SRIF was reduced by picrotoxin, a GABAA receptor antagonist, in one-third of neurons. These results suggest that SRIF exerts an inhibitory effect on medial amygdala neurons through either a direct action on SRIF receptors or a GABAergic synaptic involvement.