Anxiolytic effects of chlordiazepoxide blocked by injection of GABAA and benzodiazepine receptor antagonists in the region of the anterior basolateral amygdala of rats.

The amygdala is a structure that is often implicated in the regulation of anxiety responses. Many studies have shown that injection of benzodiazepines into the amygdala produces an anxiolytic effect. The present study was undertaken to determine whether the anxiolytic effect of administration of systemic benzodiazepine (chlordiazepoxide) might be blocked by local injection of a benzodiazepine receptor antagonist (flumazenil) or GABAA receptor antagonist (bicuculline methiodide; BMI) into the region of the anterior basolateral amygdala (BLA) of rats using an ethologically based test of anxiety, the social interaction test. Injection of flumazenil or BMI into the BLA of rats was found to reverse the anxiolytic effects of peripherally administered chlordiazepoxide. These results suggest a major role for the BLA in mediating the anxiolytic effects of benzodiazepines.