Objective To observe the effect of electroacupuncture(EA)stimulation of"Neiguan"(PC 6)at different frequencies on plasma vasoactive substance levels in myocardial ischemia-reperfusion(MIR)injury rats

so as to explore its mechanisms underlying improvement of acute myocardial ischemia.Methods A total of 40 Wistar rats were randomized into control

model

high frequency(HF

120Hz)and low frequency(LF

20Hz)groups(n=10in each group).The MIR model was established by occlusion of the anterior descending branch(ADB)of the left coronary artery for 30 min

followed by reperfusion for40 min.EA(3V

120 Hz or 20Hz)was applied to bilateral"Neiguan"(PC 6)for 50 min immediately after occlusion of ADB.Subsequently

the contents of plasma endothelin(ET)

atrial natriuretic peptide(ANP)

thromboxane B 2(TXB2)and 6-Keto-PGF1αwere assayed by radioimmunoassay

and the content of serum nitric oxide(NO)was detected by nitrate reductase method.Results Compared with the control group

the contents of plasma ET

ANP and TXB2 in the model group were significantly increased(P<0.05)

and that of plasma 6-Keto-PGF1αin the model group was notably decreased(P<0.05)

but no significant change was found in serum NO level(P>0.05).Compared with the model group

the contents of plasma ET

ANP and TXB2 were considerably decreased

and plasma 6-Keto-PGF1α and serum NO contents were obviously increased in both HF and LF groups(P<0.05).No significant differences were found between the HF and LF groups in plasma ET

ANP

TXB2 and 6-KetoPGF1αcontents(P>0.05)

but the HF EA was markedly superior to the LF EA in up-regulating the content of serum NO(P<0.05).Conclusion EA stimulation of"Neiguan"(PC 6)can down-regulate the contents of plasma ET

ANP and TXB2 and up-regulate contents of plasma 6-Keto-PGF1αand serum NO in MIR rats

which may contribute to its effect in relieving acute ischemic myocardial injury.The effect of HF EA is better than LF EA in raising blood NO level.