NEUROHUMORAL MECHANISMS OF SLEEP AND WAKEFULNESS

Resumen

Today it is well accepted that there exist at least two phases of sleep, which can be distinguished from each other both behaviorally and electrophysiologically. However, the problem of identifying the neurotransmilters responsible for sleep and wakefulness has not yet been solved. Present evidence indicates that serotonin
(5-HT) is involved in the induction and maintenance of slow wave sleep, and that norepinephrine (NE) is involved mainly in the maintenance of fast wave sleep. In view of the fact that NE also been shown to be involved in wakefulness, it is thought that 5-HT regulates slow wave sleep, and that NE regulates both fast wave sleep and wakefulness. On the other hand there is evidence that acetylcholine and GABA, though the latter to a lesser degree, could have an important role in the regulation of one or several stages of the sleep-wakefulness cycle. In view of the fact that several neurotransmitters appear to have important roles in sleep, the experimental evidence showing that it is possible to extract either from blood, cerebrospinal flud and/or brain tissue, substances which are capable of inducing sleep, is discussed. Possibly these latter techniques will allow characterization of the neurotransmitters involved in sleep and wakefulness.