Effects of the cannabinoid CB(1) receptor antagonist rimonabant on distinct measures of impulsive behavior in rats

RATIONALE: Pathological impulsivity is a prominent feature in several psychiatric disorders, but detailed understanding of the specific neuronal processes underlying impulsive behavior is as yet lacking. OBJECTIVES: As recent findings have suggested involvement of the brain cannabinoid system in impulsivity, the present study aimed at further elucidating the role of cannabinoid CB(1) receptor activation in distinct measures of impulsive behavior. MATERIALS AND METHODS: The effects of the selective cannabinoid CB(1) receptor antagonist, rimonabant (SR141716A) and agonist WIN55,212-2 were tested in various measures of impulsive behavior, namely, inhibitory control in a five-choice serial reaction time task (5-CSRTT), impulsive choice in a delayed reward paradigm, and response inhibition in a stop-signal paradigm. RESULTS: In the 5-CSRTT, SR141716A dose-dependently improved inhibitory control by decreasing the number of premature responses. Furthermore, SR141716A slightly improved attentional function, increased correct response latency, but did not affect other parameters. The CB(1) receptor agonist WIN55,212-2 did not change inhibitory control in the 5-CSRTT and only increased response latencies and errors of omissions. Coadministration of WIN55,212-2 prevented the effects of SR141716A on inhibitory control in the 5-CSRTT. Impulsive choice and response inhibition were not affected by SR141716A at any dose, whereas WIN55,212-2 slightly impaired response inhibition but did not change impulsive choice. CONCLUSIONS: The present data suggest that particularly the endocannabinoid system seems involved in some measures of impulsivity and provides further evidence for the existence of distinct forms of impulsivity that can be pharmacologically dissociated.