The neuroanatomical specificity of the anxiolytic effects ofintra-septal infusions of midazolam

Microinfusions of the benzodiazepine anxiolytic midazolam into thelateral but not the medial septum suppressed fear reactions in two testsof rat ‘anxiety’. Midazolam infusions into the lateral septal nucleiincreased open-arm exploration in the elevated plus-maze test, and blockedburying behavior in the shock-probe test, whereas midazolam infusions intothe medial septum produced neither of these anxiolytic effects. Theanxiolytic effects of midazolam in the lateral septum were partial lyblocked by pre-infusion of the benzodiazepine receptor antagonist Ro15-1788, which had no intrinsic effectsby itself. These results suggest that the anxiolytic effects of intra-septal midazolam occur, at least inpart, at GABAA-benzodiazepine receptor sites located in the lateralseptal nuclei.