【Objective】 To investigate the gender difference of the antinociceptive effect induced by intrathecal nicotinic acetylcholine receptor agonist epibatidine in rats and the potential receptor mechanisms underlying such gender difference. 【Method】 The antinociceptive behavioral test was performed to observe the difference of analgesia induced by intrathecal epibatidine

as well as the inhibition of mecamylamine on the analgesia

between male and female rats. The nAChRα4 expression was observed by immunofluorescence staining to investigate the mechanism underlying the gender difference of epibatidine-induced analgesia. 【Result】 Intrathecal injection of epibatidine induced analgesia in dose-dependent manner with more potent analgesic effect in female rat than male rat. Although non-competent antagonist of nAChR mecamylamine pretreatment partially blocked the analgesia induced by epibatidine

stronger analgesic effect maintained in female than male rats. Immunohistochemistry staining showed that nAChRα4

which mediated the analgesia of epibatidine

was expressed in the neurons of the lumber spinal dorsal horn. However

no difference in the nAChRα4 expression was detected between male and females rats. 【Conclusion】 There is gender difference in the antinociceptive effect induced by intrathecal epibatidine between male and female rats. Mechanisms other than the expression of nAChRα4 might underlie such gender difference.