The neuroanatomical specificity of the anxiolytic effects of intra-septal infusions of midazolam.

Microinfusions of the benzodiazepine anxiolytic midazolam into the lateral but not the medial septum suppressed fear reactions in two test of rat 'anxiety'. Midazolam infusions into the lateral septal nuclei increased open-arm exploration in the elevated plus-maze test, and blocked burying behavior in the shock-probe test, whereas midazolam infusions into the medial septum produced neither of these anxiolytic effects. The anxiolytic effects of midazolam in the lateral septum were partially blocked by pre-infusion of the benzodiazepine receptor antagonist Ro15-1788, which had no intrinsic effects by itself. These results suggest that the anxiolytic effects of intra-septal midazolam occur, at least in part, at GABAA-benzodiazepine receptor sites located in the lateral septal nuclei.