Effect of low doses of Delta super(9)-tetrahydrocannabinol and cannabidiol on the extinction of cocaine-induced and amphetamine-induced conditioned place preference learning in rats

• Published in: Psychopharmacology Vol. 175; no. 3; pp. 360 - 366
• Main Authors: Parker, Linda A, Burton, Page, Sorge, Robert E, Yakiwchuk, Christine, Mechoulam, Raphael
• Format: Journal Article
• Language: English
• Published: 01.09.2004
• Subjects: Cannabis
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-004-1825-7

Rationale: Using the place-preference conditioning paradigm, we evaluated the potential of the two most prominent cannabinoids found in marijuana, the psychoactive component Delta super(9)-tetrahydrocannabinol ( Delta super(9)-THC) and the nonpsychoactive component cannabidiol (CBD), to potentiate extinction of a cocaine-induced and an amphetamine-induced conditioned place preference in rats. Methods: To determine the effects of pretreatment with Delta super(9)-THC or CBD on extinction, a cocaine-induced and amphetamine-induced place preference was first established. Rats were then given an extinction trial, during which they were confined to the treatment-paired floor for 15 min. Thirty minutes prior to the extinction trial, they were injected with a low dose of Delta super(9)-THC (0.5 mg/kg), CBD (5 mg/kg) or vehicle. The potential of the CB sub(1) receptor antagonist, SR141716, to reverse the effects of Delta super(9)-THC or CBD was also evaluated. To determine the hedonic effects of CBD, one distinctive floor was paired with CBD (5 mg/kg) and another with saline. Finally, to determine the effect of Delta super(9)-THC or CBD on the establishment and/or the expression of a place preference during four cycles of conditioning trials, rats were injected with Delta super(9)-THC (0.25-1 mg/kg), CBD (5 mg/kg) or vehicle 25 min prior to receiving an injection of amphetamine followed by placement on the treatment floor; on alternate days, they received injections of vehicle followed by saline and placement on the nontreatment floor. The rats then received two test trials; on one trial they were pretreated with the cannabinoid and on the other trial with vehicle. Results: Delta super(9)-THC and CBD potentiated the extinction of both cocaine-induced and amphetamine-induced conditioned place preference learning, and this effect was not reversed by SR141716. The cannabinoids did not affect learning or retrieval, and CBD was not hedonic on its own. Conclusions: These results are the first to show that both Delta super(9)-THC, which acts on both CB1 and CB2 receptors, and CBD, which does not bind to CB sub(1) or CB sub(2) receptors, potentiate the extinction of conditioned incentive learning.