MODULATION OF DRUG REINFORCEMENT BY BEHAVIORAL REQUIREMENTS FOLLOWINGDRUG INGESTION

Eight volunteers with histories of drug abuse participated in two expe riments examining the modulation of drug choice by behavioral requirem ents following drug ingestion. Each morning subjects ingested color-co ded capsules containing triazolam (0.25mg), d-amphetamine (15 mg), or placebo and then engaged in a relaxation or a computer vigilance activ ity. Experiment 1 involved two phases (i.e. a triazolam and a d-amphet amine phase), presented in counterbalanced order. Within each phase, s ubjects were first exposed to each of two compounds (placebo and eithe r triazolam or d-amphetamine) once with each activity. Then every othe r day for 20 days subjects chose which compound they ingested with the vigilance and relaxation activities, with the restriction that they c ould not choose the same compound with both activities. Seven of eight subjects reliably chose d-amphetamine with the vigilance activity; al l subjects always chose triazolam with the relaxation activity. In exp eriment 2 (5 days' duration), after re-exposure to the color-coded com pounds used in experiment 1, subjects chose which compound (placebo, d -amphetamine or triazolam) they ingested with the vigilance activity, and on another occasion (in counterbalanced order), which they ingeste d with relaxation activity. Seven of eight subjects chose d-amphetamin e with the vigilance activity; all subjects chose triazolam with the r elaxation activity. The relaxation and vigilance activities modulated triazolam and d-amphetamine reinforcement, thereby demonstrating a new class of environmental variable that can influence drug self-administ ration.