Since the discovery some 15 years ago of benzodiazepine modulatory sites associated with GABA A receptors, great effort has gone into understanding their molecular pharmacology and into developing new anxiolytic drugs that interact selectively with them. Prominent in this research has beenthe discovery that ~-carbolines, a different chemical class from benzodiazepines, also act at these receptors but that their effects are sometimes quite different from those of the benzodiazepines.This book documents the latest discoveries in the molecular biology of the GABA A receptor and reveals how an integration of the results of research inmolecular biology, synthetic chemistry, biochemical and behavioral pharmacology, and clinical pharmacology has paved the way forthe development of ~-carbolines from substances inducing anxiety and convulsions to a novel therapy for anxiety states, achieving a behavioral selectivity through selective actions at subtypes of receptors.