Self-administration of delta 9-tetrahydrocannabinol by rats.

The present study examines the dose-response pattern of delta 9-tetrahydrocannabinol self-injection in naive rats at 80% reduced body weight and 100% body weight, both conditions with a fixed-time 1 min (FT-1) food delivery schedule. The results indicated that food deprived animals tested on a FT-1 min schedule self-injected low doses of delta 9-THC at a higher rate than those animals at 100% body weight and on a FT-1 min schedule. Animals at 80% reduced body weight without a schedule did not differ from rats self-injecting delta 9-THC at free feeding situation. These findings suggest that rats without previous history of drug dependence self-administer low doses of delta 9-THC and that the interaction between the food deprivation state and the environmental contingencies introduced by a FT-1 min schedule is a critical variable in the acquisition period.