Mechanisms of reinforcement and their relation to future developments in pharmacotherapy

The existence of brain neuronal circuitry dedicated to hedonic processes was hypothesized after the demonstration that rats would emit a response that was followed by the presentation of a small electrical current to a discrete brain region (Olds and Milner, 1954). This concept had significant implications since it suggested that behavioral pathologies related to disruptions of these processes would have underlying physiological substrates that could be corrected by appropriate pharmacotherapeutic intervention. Affective disorders and substance abuse, which clearly involve these systems, could be more effectively treated if the biological mechanisms of these processes were known. Progress has been made in the pharmacotherapy of affective disorders; however, advancements in the treatment of substance abuse generally have been more limited. Several reasons for this limited progress are related to the complexity of the variables underlying these psychosocial disorders and to the constraints of the current somewhat simplified concepts of the biological basis of hedonic processes. The experimental evidence for the underlying biological substrates of reinforcement are reviewed and how this information may be used to develop new pharmacotherapeutic approaches to substance abuse discussed.