Introduction

Pharmacological and neurophysiological studies suggest a relationship between brain serotonin and sleep.

In the past 10 years the study of sleep mechanisms has developed very rapidly and has become one of the major fields of neurophysiological and psychological research. This rapid growth is in part due to some discoveries which have changed the classical neurophysiological picture of sleep from the concept of a passive resting state of the brain to that of a heterogeneous and complicated suc cession of active phenomena.

Very seldom in the history of physiology has so much effort been devoted to the description, quantification, classification, and delimitation of such a complex phenomenon of almost totally un known function. For this reason, I find it unnecessary to present a detailed review of the phenomenology of sleep and attempt instead to discuss the mechanisms involved in sleep.

I first outline the four major concepts which have changed the classical theory of sleep. Second, I describe the neuropharmacological and histochemical data which have made possible the link between structural data and functional mechanisms. Finally, I present some recent findings which have led to the belief that a complex of monoamine-containing neurons are of para mount importance in the process under lying the succession of sleep states.

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