The cannabinoid CB1 receptor antagonist SR141716A reduces appetitive and consummatory responses for food.

RATIONALE: The CB1 receptor antagonist SR141716A reduces food intake in rats. This effect is likely to depend on modulation of reward related processes.
OBJECTIVE: To investigate the effects of SR141716A on responding for food under a second order instrumental task in which responding and consumption of food can be separated, and on Pavlovian responding for a stimulus predictive of food reward.
METHODS: Instrumental responding and pellet consumption following administration of SR141716A (0-3 mg/kg) were recorded under an FI5 min FR5(5:S) operant schedule that incorporates both a 5 min initial appetitive phase and a 25 min consummatory phase. We compared the drug-induced change in responding to that recorded following a reduction in motivational state induced by pre-feeding. In a second experiment we assessed the effects of SR141716A (0-3 mg/kg) on Pavlovian approach behaviour for a stimulus (lever) associated with food reward (CS+) and a neutral stimulus (lever) not associated with reward (CS-).
RESULTS: SR141716A reduced pellet consumption and instrumental responding during both the appetitive and consummatory phases of the second order schedule. Pre-feeding had a similar effect on responding during the appetitive phase, suggesting an effect on incentive motivation. SR141716A also blocked an enhancement of responding that occurred during the consummatory phase in pre-fed animals. SR141716A and pre-feeding had no effect on responding in the Pavlovian autoshaping paradigm.
CONCLUSIONS: SR141716A impacts on motivational processes in both the appetitive and consummatory phases of feeding behaviour.