Serotonin and Neuroendocrine Regulation

Serotonin was first isolated from serum by Rapport et al. 1,2 and was subsequently found to be present in the brain and to function as a neurotransmitter. 3–5 Over the course of the last 50 years there has been an explosion of knowledge of the serotonergic system. The relatively recent development of selective serotonin reuptake inhibitors (SSRIs) and their effectiveness in treating a vast array of conditions (e.g. depression, anxiety, obesity, bulimia, aggression, obsessive compulsive disorder and post-traumatic stress disorder) has only served to heighten interest into the multitude of functions that serotonin influences via its actions within the central nervous system. 614 Two of these functions of serotonin—the activation of various neuroendocrine systems and modulation of the sleep/wake cycle—wiU be dealt with in this review. Particular emphasis will be placed on the possible role that neuroendocrine systems may play in mediating some of the effects of serotonin on the three major components of the sleep/wake cycle: wakefulness, slow wave sleep (SWS) and rapid eye-movement (REM) sleep