Role of the cannabinoid system in the effects induced by nicotine on anxiety-like behaviour in mice.

RATIONALE: Acute behavioural effects and motivational responses induced by nicotine can be modulated by the endocannabinoid system supporting the existence of a physiological interaction between these two systems.
OBJECTIVES: The present study was designed to examine the possible involvement of the cannabinoid system in the anxiolytic- and anxiogenic-like responses induced by nicotine in mice.
METHODS: Animals were only exposed once to nicotine. The acute administration of low (0.05) or high (0.8 mg/kg, s.c.) doses of nicotine produced opposite effects in the elevated plus-maze, i.e. anxiolytic- and anxiogenic-like responses, respectively. The effects of the pretreatment with the CB1 cannabinoid receptor antagonist, rimonabant (0.25, 0.5 and 1 mg/kg, i.p.), and the cannabinoid agonist, delta9-tetrahydrocannabinol (delta9-THC, 0.1 mg/kg, ip), were evaluated on the anxiolytic- and anxiogenic-like responses induced by nicotine.
RESULTS: Rimonabant completely abolished nicotine-induced anxiolytic-like effects and increased the anxiogenic-like responses of nicotine, suggesting an involvement of CB1 receptors in these behavioural responses. On the other hand, delta9-THC failed to modify nicotine anxiolytic-like responses but attenuated its anxiogenic-like effects. In addition, the association of non-effective doses of delta9-THC and nicotine produced clear anxiolytic-like responses.
CONCLUSIONS: These results demonstrate that the endogenous cannabinoid system is involved in the regulation of nicotine anxiety-like behaviour in mice and provide new findings to support the use of cannabinoid antagonists in the treatment of tobacco addiction.