Flumazenil blocks the anxiolytic action of allopregnanolone

In the burying behaviour test allopregnanolone (0.5 mg/rat) reduced the cumulative time of burying, interpreted as a reduction in anxiety. The selective benzodiazepine antagonist, flumazenil (5 and 10 mg/kg), did not affect the burying behaviour when administered alone but effectively prevented the reduction produced by allopregnanolone. No scheme modified the ambulatory behaviour, thus suggesting that the effect of these treatments was selective on experimental anxiety. These results indicate that the anxiolytic actions of neurosteroids are most likely mediated via the stimulation of GABAA receptors. Data are discussed on the basis of such relationships.