This text is the written form of the proceedings of a satellite symposium associated with the 1988-meeting of the Society for Neu roscience. The symposium was held 12 November 1988 in the auditor ium of the Addictions Research Foundation, Toronto, Canada. The ac tual writing took place across the months following the symposium. The symposium was sponsored by the Addictions Research Foundation, Toronto, Canada, the National Institute on Alcohol Abuse and Alcoholism, U. S. A. , and Rensselaer, Troy, NY, U. S. A. Du Pont Pharmaceuticals provided some financial assistance. Contributors also received specific support for their own projects and these are ac knowledged at the end of each chapter. The accomplishment of science involves the efforts of many persons and their organizations. That is surely manifest in the work presented here. Modern science is very expensive and, consequently, financial resouces must be developed and distributed wisely. Those who facilitate this basic function have the appreciation of those of us who need the resources to do our work. There are a large number of individuals whose names will not appear in these pages that make sub stantial contributions. We are thankful for their daily contributions. The people who provide the money, those who distribute it, and those who help us do our work have the legitimate expectation that the sci entists who use the resources will use it prudently. We hope that your expectations are fulfilled, and sincerely appreciate your efforts.