Objective To observe the therapeutic effect of ear-electroacupuncture(Ear-EA) on dysmenorrhea in patients with endometriosis and to explore its underlying mechanism.Methods A total of 80 endometriosis patients were randomly and equally divided into ear-EA group and body-EA group.EA(50 Hz

0.5-0.8 mA) was applied to auricular points(Uterus

Subcortex

Shenmen

Endocrine

etc.) and body acupoints [Tianshu(ST 25)

Qihai(CV 6)

Guanyuan(CV 4)

Sanyinjiao(SP 6)

Diji(SP 8)

Uterus(EX-CA 1)

etc.] respectively for 30 min

once every other day for 3 months.Dysmenorrhea severity score(DSS) was assessed and plasma prostaglandin(PGE2) and 6-Keto-PGF1α levels detected by radioimmunoassay.Results Compared with pre-treatment

DSS lowered significantly during the 1st and 2nd menstrual cycle in body-EA group

and during the 1st

2nd and 3rd menstruation in ear-EA group;and the DSS of ear-EA group during the 3rd menstruation was evidently lower than that of body-EA group(P<0.05).During the 3rd menstrual onset after the treatment

plasma PGE2 contents in both groups decreased obviously(P<0.01)

and plasma 6-Keto-PGF1α levels increased considerably in comparison with pre-treatment(P<0.01).Comparison between two groups during the 3rd menstruation showed that plasma PGE2 level of ear-EA group was markedly lower than that of body-EA group

and 6-Keto-PGF1α level of ear-EA group was significantly higher than that of body-EA group(P<0.05).No significant difference was found between two groups in clinical therapeutic effect(P>0.05).ConclusionBoth ear-EA and body-EA can effectively relieve endometriosis-induced dysmenorrhea

and the former is superior to the later in reducing pain severity

which may be closely related to their effects in reducing plasma PGE2 and raising 6-Keto-PGF1α level.