Effects of benzodiazepine agonist, inverse agonist and antagonist drugs in the mouse staircase test.

This study examined the effects of the benzodiazepine agonist midazolam and inverse agonist noreleagnine independently and in conjunction with the antagonist flumazenil in the mouse staircase test. According to this paradigm, the numbers of steps ascended (NSA) and rears (NR) reflect locomotor activity and anxiety, respectively. Midazolam reduced NR at doses that did not affect NSA; this NR-lowering effect was blocked by flumazenil. Noreleagnine increased NR at doses that did not affect NSA; this NR-elevating effect was also blocked by flumazenil. Effective antagonist doses of flumazenil alone had no effect on NR or NSA. The exactly opposite effects of midazolam and noreleagnine on NR and their antagonism by flumazenil are consistent with the postulated activities of these drugs at benzodiazepine receptors.