ObjectiveTo study the possible relation of pain perception with estrogen in rats. MethodsA total of 16 rats were equally divided into two groups: an ovariectomization group (OVX) and an ovariectomization plus E2-treatment group (OVX+E2). Animals in OVX group were ovariectomized to decrease the ovarian hormone level, and those in the OVX+E2 group were treated with estrogen one week after ovariectomization. 2-MeSADP, a selective agonist of P2Y1 receptor, was injected into the hindpaw of the rats in both groups. The mechanical pain thresholds were observed by behavioral tests, and the expression of P2Y1 in the dorsal root ganglia were examined by RT-PCR in the two groups. ResultsThe mechanical pain threshold of rats in OVX+E2 group was significantly increased compared with that of rats in OVX group(P=0.014). After 2-MeSADP injection, the mechanical pain threshold of rats in OVX group underwent no significant change, and that of rats in OVX+E2 group was deceased. RT-PCR result showed that P2Y1 mRNA expression in the DRG in OVX+E2 group was significantly increased compared with that in OVX group(P<0.05) .ConclusionOur findings indicate that estrogen may influence the peripheral mechanical pain threshold by increasing the expression of P2Y1 receptors in DRG.