COCAINE SELF-ADMINISTRATION INCREASED BY COMPOUNDING DISCRIMINATIVE STIMULI

Presenting independently established discriminative stimuli in compoun d can substantially increase response rates under food and shock-avoid ance schedules. To determine whether this effect extends to drug self- administration, rats were trained to press a lever to receive cocaine intravenously. A tone and a light were independently established as di scriminative stimuli for cocaine self-administration, then presented i n combination in a stimulus-compounding test. Compared to tone and lig ht alone, the tone-plus-light compound stimulus increased responding a pproximately three-fold when cocaine was withheld during testing, and it increased drug intake approximately two-fold when cocaine was made available during testing. Compounding did not increase responding afte r training in a truly random control condition where tone and light we re presented uncorrelated with the availability of cocaine. The result s obtained with this animal model of drug abuse define conditions unde r which combinations of environmental stimuli might substantially incr ease human drug use.