Reduction of heroin self-administration in baboons by manipulation of behavioral and pharmacological conditions

Baboons responded on a discrete-trial choice task on which trials occurred every three hours throughout the day. Trials involved choosing between several mutually exclusive options, one of which was always associated with intravenous infusion of a unit dose of heroin. Experiments were undertaken to reduce the selection of the heroin option. Experiment 1 used methods analogous to clinical situations involving opioid maintenance and subsequent detoxification. During initial baseline conditions, baboons consistently preferred an option of heroin and food over an option of saline and food. Selection of heroin was almost entirely eliminated when there was a mutually exclusive choice between heroin and food and chronic non-contingent morphine was administered. Decreasing the dose of non-contingent morphine produced an increased selection of heroin. In Experiment 2, initial baseline conditions were similar to Experiment 1. Food availability was subsequently made contingent upon selection of options involving progressively lower doses of contingent heroin. These manipulations reduced heroin intake to about 15% of baseline levels. The experiments demonstrate the utility of animal models for studying procedures for the reduction of opiate self-administration.