This project is designed to selectively breed rats that are differentially sensitive to the central nervous system effects of acutely administered ethanol. Starting with a genetically heterogeneous population of rats (HS/Nih), short sleep (SS) and long sleep (LS) rats will be produced by applying selection pressure on the ataxic response to acute administration of ethanol. Two replicate lines will be developed in the SS direction and two replicate lines in the LS direction by restricting controlled matings to within line. In addition, two control lines, in which no selection pressure is applied, will be developed. The response to selection for sleep time, the behavioral trait, is determined each generation, as mating pairs are chosen for the successive generation. Neurophysiological and biochemical traits, that are known to be genetically correlated with sleep time in SS and LS mice will be monitored every third generation. The major rationale for the project is to determine the species generality of similar studies already carried out in mice and to provide a larger animal model for neurobiological studies on genetic differences in response to ethanol. The rat has been well-studied neuroanatomically and neuropharmacologically, and allows the use of brain transplants as well as electrophysiological studies in freely-moving animals which are difficult or impossible in mice.