Delta-9-tetrahydrocannabinol enhances food reinforcement in a mouse operant conflict test

Abstract

Rationale: Cannabinoid compounds are known to regulate feeding behavior by modulating the hedonic and/or the incentive properties of food.

Objectives: The aim of this work was to determine the involvement of the cannabinoid system in food reinforcement associated with a conflict situation generated by stress.

Methods: Mice were trained on a fixed ratio 1 schedule of reinforcement to obtain standard, chocolate-flavored or fat-enriched pellets. Once the acquisition criteria were achieved, the reinforced lever press was paired with foot-shock exposure, and the effects of Delta(9)-tetrahydrocannabinol (THC; 1 mg/kg) were evaluated in this conflict paradigm.

Results: THC did not modify the operant response in mice trained with standard pellets. In contrast, THC improved the instrumental performance of mice trained with chocolate-flavored and fat-enriched pellets. However, the cannabinoid agonist did not fully restore the baseline responses obtained previous to foot-shock delivery. THC ameliorated the performance to obtain high palatable food in this conflict test in both food-restricted and sated mice. The effects of THC on food reinforcement seem to be long-lasting since mice previously treated with this compound showed a better recovery of the instrumental behavior after foot-shock exposure.

Conclusions: These findings reveal that the cannabinoid system is involved in the regulation of goal-directed responses towards high palatable and high caloric food under stressful situations.