Rationale: Cannabinoids have been shown to produce greater behavioral effects in female than male rats. Although central nervous system CB(1) receptors are known to mediate cannabinoid-induced behavioral effects in male rats, it is not known whether the same is true for females.
Objective: To determine if cannabinoid-induced antinociception and catalepsy are similarly mediated by central CB(1) receptors in male and female rats.
Methods: The ability of SR141716A, a CB(1) receptor selective antagonist, administered ICV (1-1000 microg) or IT (1-600 microg) to block 10 mg/kg IP delta(9)-THC-induced antinociception (paw pressure) and catalepsy (bar test), was compared in male and female rats.
Results: Delta(9)-THC alone produced slightly greater antinociception, and significantly greater catalepsy in females than males. When administered ICV, SR141716A partially antagonized delta(9)-THC-induced antinociception in both females and males. IT SR141716A also antagonized delta(9)-THC-induced antinociception in both sexes; it was slightly more potent in males but equally effective in males and females. SR141716A antagonized delta(9)-THC-induced catalepsy in a similar manner in males and females when given ICV or IT.
Conclusions: These results confirm that delta(9)-THC-induced behavioral effects are mediated by central CB(1) receptors in male and female rats.