The ability of high doses of flumazenil to antagonize ethanol-induced sedation was assessed via ethanol-induced loss of the righting reflex (LRR) in rats. Ethanol (3.5-5 g kg-1 i,p) produces a dose-dependent increase in the proportion of animals presenting a LRR response. Flumazenil (0.1 to 1 mg kg-1 i.p) was ineffective in preventing the suppression of the righting reflex and even aggravated it for ethanol dosages of 3.5 and 4.0 g kg-1. These data support the view that flumazenil has no effective 'anti-ethanol' properties. Conversely, the prolongation of mean sleep time provoked by the antidote could be related to the suppression of a putative endogenous inverse-agonist activity at the benzodiazepine receptor, which could be implicated in the mechanism of the acute tolerance to ethanol.
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