Dedicated to Professor Albert Herz, a leading investigator in opioid research, this book provides comprehensive information on the biology of exogenous and endogenous opioids. Contributions by experts in the field discuss recent advances and provide systematic, up-to-date reviews of the physiology and pharmacology of opioids, as well as on the cellular and molecular mechanisms underlying opioid actions. In recognition of the diverse methodologies now available to researchers, each chapter details the approaches used to address a specific issue and provides an in-depth analysis of the data obtained by these various experimental approaches. The clinical relevance of recent findings, as well as future directions, in opioid research are also discussed. This volume thus represents a timely and invaluable sourcebook for researchers, clinicians, and students interested in opioids and peptidergic systems.