ACUTE ADMINISTRATION OF THE CB1 CANNABINOID RECEPTOR ANTAGONIST SR 141716A INDUCES ANXIETY-LIKE RESPONSES IN THE RAT

ANIMAL models have revealed that psychoactive cannabinoids induce both anxiolytic and anxiety-like reactions which are dose- and context-dep endent. In the present study we examined the acute actions of the CB1 cannabinoid receptor antagonist SR 141716A in both the defensive withd rawal test and the elevated plus-maze in rats. Acute administration of SR 141716A (0.1, 1 and 3 mg kg(-1)) induced defensive responses in bo th anxiety tests, at a dose of 3 mg kg(-1). This dose had no effect on horizontal locomotor activity and did not activate the hypothalamus-p ituitary-adrenal axis, although several cannabinoid withdrawal-like be havioural symptoms were observed. These results demonstrate that block ade of the endogenous cannabinoid tone might induce anxiety-like respo nses in rats.