Behavior reinforced by orally delivered cocaine will be studied in 8 rhesus monkeys.
One aim i s to develop an experimental preparation that is durable and easy to manage so that factors controlling the maintenance and elimination of cocaine-reinforced behavior can be studied in long-term, systematic, parametric experiments. The chambers that will serve as monkey's living quarters will also function as experimental chambers. Delivery of liquids and (in one experiment) food will be contingent upon a subject's behavior. The principal independent variables will be (1) the available liquid -- a cocaine solution, the vehicle (water), or a solution containing a non-drug reinforcer (saccharin), (2) the amount of behavior subjects must emit prior to drug delivery (specifically, the size of a fixed-ratio reinforcement schedule), (3) feeding conditions (restricted feeding vs. free feeding), and (4) the period as a reinforcer by initially presenting all of a subject's daily food allotment within experimental sessions, then gradually adding increasing amounts of cocaine to the liquid available within sessions, and finally fading food from the session. Five experiments will then be conducted, to characterize as extensively as possible the reinforcing effects of orally delivered cocaine solutions. The first and second experiments will examine the reinforcing effects of solutions containing different concentrations (i.e., amounts) of cocaine in relation to concurrently available water; fixed-ratio size and feeding conditions will be manipulated. In Experiment 3, cocaine solutions will be available at both spouts, and the relative reinforcing effects of different cocaine concentrations will be investigated. The effects of chronic (22- hr/day) access to cocaine on cocaine self-administration and on other behavior will be explored in Experiment 4; the question of whether tolerance develops to various effects of cocaine will be examined, as will possible disruptions of behavior when access to cocaine is terminated. Finally, the effects on cocaine self-administration of concurrent access to a non-drug reinforcer (saccharin) will be parametrically studied both by varying cocaine concentration and saccharin concentration, and by varying the consequences of responding -- delivery of saccharin and cocaine vs. delivery of saccharin or cocaine (Experiment 5). As well as providing a body of data concerning the reinforcing effects of orally delivered cocaine, which for the most part is currently unavailable, the study will furnish a group of 8 monkeys with extended histories of cocaine self- administration, which can serve as subjects for future research that will (1) analyze the bases of individual differences in cocaine self- administration and (2) examine intervention strategies aimed at curtailing and eliminating cocaine self-administration behavior.
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