We examined the effects of an L-type Ca2+ channel blocker, nilvadipine (0.5 and 2.0 mg/kg), and that of a T-type Ca2+ channel blocker, flunarizine (10.0 and 40.0 mg/kg), on the hypnotic potency of both a benzodiazepine (BZ)-hypnotic, triazolam (1.0 mg/kg), and a non-BZ hypnotic, zolpidem (20.0 mg/kg), in rats. The polysomnogram was recorded for 6 h after administration of the vehicle solution alone, or after one of the Ca2+ channel blockers, with or without one of the hypnotics. Both Ca2+ channel blockers prolonged the increased total time of non-rapid eye movement (non-REM) sleep induced by either hypnotic. In the case of triazolam, however, the non-REM sleep-enhancing effect induced by nilvadipine was greater than that induced by flunarizine. These findings indicate that the hypnotic action of triazolam is potentiated more strongly by an L-type Ca2+ channel blocker than by a T-type Ca2+ channel blocker.