OBJECTIVETo explore the protective effects of electroacupuncture preconditioning at "Neiguan" (PC 6) on myocardial ischemia reperfusion injury (MIRI) and the mechanism.

METHODSForty-eight male Wistar rats were randomly divided into a sham operation group (group N), a MIRI group (group M) and an electroacupuncture group (group E). The MIRI model was generated by ligating the left anterior descending artery (LAD) for 30 min followed by reperfusion for 120 min. The partition sutures in group N were passed under the LAD without ligation. The rats in group E were pretreated with electroacupuncture applied at bilateral "Neiguan" (PC 6) for 20 min once a day on 3 consecutive days before ischemia. The area at risk and infarct size and the serum levels of CK-MB and LDH were measured. The morphological changes were observed by light microscopy. The mRNA expressions of delta and kappa opioid receptor (DOR and KOR) were determined by real-time RT-PCR.

RESULTSThe myocardial infarct size in group E was significant smaller than that in group M (P < 0.05). The contents of CK-MB and LDH were (980 +/- 92) U/L and (2 743 +/- 124) U/L in group M which were significant higher than (312 +/- 41) U/L and (530 +/- 56) U/L in group N (both P < 0.01) and (572 +/- 70) U/L and (1 819 +/- 97) U/L in group E (both P < 0.01). The mRNA expressions of DOR and KOR had no significant difference between group M and N (both P > 0.05), while the DOR expression in group E was significant higher than that in group M and N (both P < 0.01). There was no significant difference in KOR expression among three groups (all P > 0.05).

CONCLUSIONThe cardiac protective effects of electroacupuncture preconditioning at "Neiguan" (PC 6) on MIRI may be mediated by increasing expression of delta opioid receptor in myocardium.