Further behavioural evidence for the selective sedative action of zolpidem

Small doses of benzodiazepines stimulate behavioural output in experimental animals in a variety of situations. Zolpidem, which displaces benzodiazepines from their binding sites, however, has been shown to exert preferential sedative activity. In order to investigate whether small doses of zolpidem would also have stimulant effects, the actions of zolpidem and chlordiazepoxide were compared in three procedures which are sensitive to the behavioural-facilitating effects of benzodiazepines in rats. A small dose of chlordiazepoxide (3.0 mg/kg) increased locomotion in an open field whereas a large dose (30 mg/kg) suppressed this behaviour. Zolpidem (0.3-3.0 mg/kg) only decreased locomotion. The effects of both chlordiazepoxide and zolpidem were antagonised by flumazenil. Chlordiazepoxide (2.5-10 mg/kg) increased the intake of food in rats habituated to a daily feeding schedule but similar doses of zolpidem neither increased nor decreased the intake of food. Rates of punished operant responding were increased by chlordiazepoxide (3.0-30 mg/kg) but zolpidem (1.0-4.0 mg/kg) produced no such anti-punishment effect and suppressed responding at the large dose. These results show that zolpidem does not increase behavioural output in situations which are sensitive to the stimulant effects of benzodiazepines and further emphasize the selective sedative activity of this drug.