HYPNOTIC AND HYPOTHERMIC EFFECTS OF MELATONIN ON DAYTIME SLEEP IN HUMANS - LACK OF ANTAGONISM BY FLUMAZENIL

In this double-blind, placebo-controlled study we investigated whether 10 mg flumazenil, a pure benzodiazepine antagonist, can block the hyp notic and hypothermic effects of 3 mg melatonin. The design comprised four 7-h (1200-1900 h) testing periods, preceded by a 'no-treatment' a daptation period of the '7/13' sleep-wake paradigm. Six young healthy adult males were paid to participate. During each experimental period, tablets were administered at 1145 h (flumazenil or placebo) and at 12 00 h (melatonin or placebo) in a randomized, double-blind, partially r epeated Latin square design. Polysomnographic recordings and core body temperature recordings revealed that melatonin, either in combination with placebo or with flumazenil, significantly increased the amounts of sleep, and decreased core body temperature in comparison with place bo alone or the combination of flumazenil plus placebo. These results do not support the hypothesis that melatonin exerts its hypothermic an d hypnotic effects via the central benzodiazepine receptors.