Medial amygdala modulation of predator odor-induced unconditioned fear in the rat.

This study examined the participation of the medial amygdala (MeA) in unconditioned fear. Rats received ibotenic acid lesions in the MeA or central amygdala (CeA) prior to cat-odor exposure. MeA-lesioned rats exhibited a significant reduction in freezing duration and made frequent contact with a cloth containing cat odor. In contrast, CeA lesions had no significant effects on unconditioned fear. The freezing reduction produced by MeA lesions was not due to a performance deficit because MeA-lesioned rats, unlike CeA-lesioned rats, were capable of freezing in postshock test intervals. Furthermore, MeA lesions did not alter olfactory function and general locomotor activity. Results demonstrate that the MeA plays a major role in modulating predator odor-induced unconditioned fear.