Effects of the cannabinoid receptor agonist win 55,212-2 on operant behavior and locomotor activity in rats

Cannabinoids influence the motivational state of a subject and affect motor behavior. In the present study, we examined the acute effects of the cannabinoid (CB) receptor agonist WIN 55,212-2 (WIN) in three different doses (0.6, 1.2 and 1.8 mg/kg) on the performance of rats in a progressive ratio operant behavior task and on locomotor activity. WIN dose-dependently reduced the break point and the total number of lever-presses under a progressive ratio schedule. A food preference test revealed a preference for freely available casein pellets over lab chow in all treatment groups, indicating no WIN-effects on primary motivation. There was a significant reduction in the amount of casein pellets consumed by animals treated with 1.8 mg/kg WIN. Locomotor activity in the open field was increased by 0.6 mg/kg, but not by higher doses of WIN. These data show that administration of the synthetic cannabinoid receptor agonist WIN leads to dose-dependent alterations of the performance in an operant behavior task and of motor behavior. We confirm previous findings of dose-dependent motor stimulating and inhibiting effects of cannabinoids, and show an impairment of a complex operant behavior at higher doses of WIN. (C) 2004 Elsevier Inc. All rights reserved.