Conditioned place preference induced by delta 9-tetrahydrocannabinol: comparison with cocaine, morphine, and food reward.

The rewarding property of delta 9-tetrahydrocannabinol (THC), the psychoactive constituent of marijuana and hashish, was studied using the conditioned place preference paradigm, and compared to that of cocaine, morphine, and food reward. The results of Experiment 1 demonstrated that 2.0 and 4.0 mg/kg doses produced a reliable shift in preference for the THC-paired compartment. The THC place preference observed at 2.0 and 4.0 mg/kg was nearly equivalent to that produced by low doses of cocaine (5.0 mg/kg), morphine (4.0 mg/kg), and food in non food-deprived animals. The second experiment used a different conditioning procedure that included a washout period for THC. The results of Experiment 2 demonstrated that a THC place preference could be obtained using a lower dose of THC (1.0 mg/kg), and that this THC place preference was equivalent to that produced by 10 mg/kg cocaine. At higher doses (2.0 and 4.0 mg/kg), THC produced a dose-dependent place aversion. These results suggest that THC's action on brain reward substrates, previously demonstrated by electrical brain stimulation reward, in vivo brain microdialysis, and in vivo brain electrochemistry studies, reflects itself behaviorally in increased appetitive motivational value for environmental stimuli associated with ingestion of marijuana and hashish.