The influence of behavioral and pharmacological history on the reinforcing effects of cocaine in rhesus monkeys.

Animal models of drug self-administration have been shown to be valid predictors of human drug abuse (Griffiths et al. 1980; Johanson 1978; Johanson and Schuster 1981; Spealman and Goldberg 1978; Woolverton and Nader 1990). In drug self-administration studies, if responding leading to the presentation of the drug occurs at higher rates than vehicle-maintained responding, then the drug is said to function as a positive reinforcer and have abuse liability. The focus of the research described in this chapter will be to examine the interactions of several environmental and pharmacological variables with the reinforcing effects of cocaine in rhesus monkeys, with emphasis on the long-term effects of these experimental histories. One of the goals of this chapter will be to address technical or methodological issues regarding animal models of drug selfadministration. To this end, published data as well as preliminary data will be presented. Although the scientific community urges the presentation of group data, most animal experiments in behavioral pharmacology are conducted on an individual-subject basis. Consequently, to highlight further the methodological issues regarding the influence of environmental and pharmacological variables in modifying cocaine self-administration, most of the data presented will be individual-subject data, rather than group data.