Serotonin has long been known to have important roles in many systems of the body that have important roles in health and disease. As represented by several of the chapters by a number of leading researchers in the serotonin field, these roles implicate a deep evolutionary history for serotonin, which is demonstrated by studies in a range of vertebrate and non-vertebrate model systems. In many areas of medicine, even those in which serotonin has long been known to play a role, the importance of serotonin is still emerging. This volume considers many of these areas, including such well-established areas as the study of anxiety, depression and alcoholism, in which new information is emerging. This book examines a wide range of systems and conditions in which serotonin is fundamentally important and which provide novel avenues of exploration for the development of therapeutic approaches to treat these conditions.