THE SEPTUM AND AMYGDALA DIFFERENTIALLY MEDIATE THE ANXIOLYTIC EFFECTSOF BENZODIAZEPINES

Microinfusions of a benzodiazepine anxiolytic (midazolam) into the sep tum or the amygdala suppressed different fear reactions in two tests o f rat ''anxiety''. Septal infusions increased open-arm activity in the plus-maze test and decreased burying behavior in the shock-probe test whereas amygdaloid infusions produced neither of these antianxiety ef fects. Amygdaloid infusions, however, dramatically impaired shock-prob e avoidance, an antianxiety effect not produced by the septal infusion s. Infusions of the benzodiazepine receptor antagonist Ro 15-1788 (flu mazenil) blocked each of these specific, anti-fear effects of midazola m without producing intrinsic effects by itself. These results suggest that benzodiazepine receptor systems within the amygdala and the sept um differentially mediate specific fear reactions.