COCAINE INDUCED CONDITIONED TASTE AVERSIONS AND SELF ADMINISTRATION IN THE SQUIRREL MONKEY (Saimiri sciureus)

Abstract

Stimuli paired with drug injections can either maintain or suppress responding, depending upon the relationship between those stimuli and the delivery of the drug. In order to assess the role of prior history on this relationship, the effect of previous exposure to cocaine under a maintenance schedule of self-administration or a conditioned taste aversion schedule was examined. Four experimentally naive squirrel monkeys (Saimiri sciureus) initially responded under a FI30(FR30:S) schedule of food presentation. Each FR30 completed produced 2 sec illumination of green light and the first FR30 completed following the elapse of a 30 min interval produced 25 banana pellets in addition to the presence of 5 min of green light. Once responding was stable, the monkeys were placed into two groups matched for weight, rate of responding, and quarter-life. One group was exposed to an operant version of a conditioned taste aversion (CTA) paradigm first, and then later to a cocaine self-administration (SA) paradigm. The other group was exposed to the same conditions but in reverse order. In the operant CTA design the brief stimulus following each FR30 was 2 sec of red light. Twenty five sucrose pellets were delivered at the end of the first completed FR30 once the 30 min interval elapsed along with 5 min of red light and a 0.3mg/kg cocaine injection i.m. (thigh). The self-administration design was very similar to the CTA design, however the stimulus light was green, 25 banana pellets were presented along with a 0.3mg/kg cocaine injection i.m. (thigh) upon the completion of the schedule requirements. When drug naive subjects were exposed to the CTA procedure first their rate of responding dropped significantly from a baseline of 0.71 responses per sec to 0.35 responses per sec, t(8) = 6.62, p< 0.0001. When these same subjects were then exposed to the cocaine self-administration paradigm they responded at 43 percent of their pre-drug food maintenance rates. When drug naive subjects were exposed to the self-administration procedure first they responded at 66 percent of their food maintenance rate of responding. This group was then exposed to the CTA procedure resulting in no significant change in baseline responding t(8) = 1.51, N.S. This study shows that the same dose of cocaine can be used in a CTA design to decrease responding and a self-administration design to maintain responding, that prior exposure to CTA reduced the rate of responding under drug maintenance, and prior exposure to a self-administration design will decrease the effect of CTA.