Objective To observe the effect of electroacupuncture(EA) on plasma thromboxane B2(TXB2) and 6-keto-prostaglandin F1α(6-keto-PGF1α) levels in dysmenorrhea rats in order to investigate its mechanism underlying relief of primary dysmenorrhea and specificity of acupoint efficacy.Methods Female SD rats with diestrus were randomly divided into saline control(control)

model

EA Sanyinjiao(SP 6)

EA Xuehai(SP 10)

EA Xuanzhong(GB 39) and EA non-acupoint(NAP) groups

with 10 rats in each.Dysmenorrhea model was established by subcutaneous injection of Estradiol Benzoate(0.5 mg/rat on the 1st and 10th day

and 0.2 mg/rat from the 2nd to the 9th day) and intraperitoneal injection of Oxytocin(0.2 mL/rat

1 h after last injection of Estradiol Benzoate on the 10th day).EA was applied to bilateral SP 6

SP 10

GB 39

and non-acupoint(the mid-point between the Gallbladder and Stomach meridian at the GB 39 level) for 20 min.The latency and score of writhing were recorded for 20 min.Plasma TXB2 and 6-keto-PGF1α contents were detected by radioimmunoassay.Results Compared with the control group

the latency of writhing in the model group was shortened considerably(P<0.01)

and the writhing score was increased significantly(P<0.01).In comparison with the model group

the writhing latency was increased significantly only in the EA-SP 6 group(P<0.05)

and the writhing scores in the EA-SP 6

EA-SP 10

EA-GB 39 and EA-NAP groups were reduced remarkably(P<0.01).Plasma TXB2 content and the ratio of TXB2/6-keto-PGF1α were significantly higher in the model group than in the control group(P<0.01).Compared to the model group

plasma TXB2 levels and the ratios of TXB2/6-keto-PGF1α in the EA-SP 6

EA-SP 10

EA-GB 39 and EA-NAP groups were downregulated markedly(P<0.05

P<0.01)

while plasma 6-keto-PGF1α was upregulated strikingly only in the EA-SP 6 group(P<0.05).No significant differences were found among the EA-SP 6

EA-SP 10

EA-GB 39 and EA-NAP groups in the writhing latency and writhing score

plasma TXB2 and 6-keto-PGF1α levels(P>0.05).Conclusion EA can relieve pain reaction in dysmenorrhea rats

which may be closely associated with its effects in downregulating plasma TXB2

upregulating plasma 6-keto-PGF1α content

and balancing plasma TXB2 /6-keto-PGF1α.The effect of EA of SP 6 is relatively better.