The long term objectives of this research project are to identify and characterize beharioral, pharmacological, and environmental factors that affect drug-taking behavior, and to establish some general principles that relate to drug-taking behavior. In the upcoming grant period, the focus of the research wil be on the discriminative, reinforcing and direct actions of narcotis on operant behavior. Among the studies proposed are ones investigating the discriminative stimulus effects of the d-isomers of several narcotics, the ability of animals to discriminate between narcotic. That are though to act via different receptors, the effect of drug dependence on the reinforcing effects of drugs, the sterospecific nature of the reinforcing effect of narcotics, the ability of some narcotic drugs to attenuate punished responding, and the development of supersensitivity to narcotic antagonists. Additional projects will be concerned with the actions of narcotics and related drugs on systems involved with pain, consummatory behavior, and respiration. Several of the projects are involved with narcotic drugs that exert their actions through different narcotic receptor types. The projects utilize a broad set of different species: rhesus monkeys, pigeons, rats, mice and rabbits will be used in attempts to establish generality of results across situations and species.