Influence of delta9-tetrahydrocannabinol on partial reinforcement effects.

Two experiments were performed with rats trained with either continuous reinforcement (food) or random 50% partial reinforcement for running in a straight alley. Half the rat were trained with daily injections of 0.5 mg/kg delta9-tetrahydrocannabinol (THC) and half with vehicle injections, all animals being extinguished with vehicle injections in Expt. 1 and with THC injections in Expt. 2. The partial reinforcement acquistion effect was abolished by THC during training; the partial reinforcement extinction effect was abolished by THC either during training of during extinction. In these respects THC resembles amylobarbitone and alcohol.