This book provides an update on sigma receptors, and summarizes recent advances in the medicinal chemistry, molecular biology, and cell biology of sigma receptors. It describes the functional effects mediated by these receptors and the potential clinical implications of these actions. This information is put in a historical perspective to help newcomers to the field successfully navigate the confusing early history surrounding these proteins, and provides a launching point from which future studies and research directions can easily be developed. Major advances in our understanding of sigma receptors have been made during the past few years. This book will facilitate exciting new research that could lead to significant advances in the treatment of neurologic, psychiatric, cardiovascular, immunologic, and gastrointestinal disorders through a better understanding of sigma receptors.