EFFECTS OF MELATONIN ON SLEEP AND NEUROCHEMISTRY IN THE RAT

Abstract

The effects of intraperitoneally administered melatonin on sleep and brain neurochemistry in the rat were studied by use of EEG recording and standard fluorescence techniques. Melatonin, 10 mg/kg, reduced time to sleep onset and time spent awake but increased both slow wave and paradoxical sleep. Qualitatively similar but smaller effects were produced by a dose of 2.5 mg/kg. Neither dose of melatonin altered normal EEG patterns or disrupted normal sleep behaviour. Melatonin, 20 mg/kg, did not significantly alter concentrations of tryptophan, 5‐hydroxytryptamine, 5‐hydroxyindoleacetic acid, noradrenaline or dopamine in any part of the brain. It is concluded that the sleep promoting activity of melatonin cannot be related to gross changes in brain indoleamine and catecholamine levels. 1982 British Pharmacological Society