Hao S, Takahata O, Iwasaki H
Department of Anesthesiology & Critical Care Medicine, Asahikawa Medical College, Midorigaoka-Higashi, 2-1-1-1, 078-8510, Asahikawa, Japan.
Neurosci Lett. 2000 Jun 16;287(1):9-12. doi: 10.1016/s0304-3940(00)01155-1.
Endomorphin-1 is a novel endogenous mu-opioid peptide. In this study, we examined the effects of 2 Hz electroacupuncture in the rat tail flick test and the formalin test (a persistent noxious model). Moreover, we investigated if the electroacupuncture potentiated the effect of intrathecal endomorphin-1. The results demonstrated that electroacupuncture alone produced a significant antinociception in the tail flick test, but not in the formalin test, and that intrathecal endomorphin-1 dose-dependently suppressed the biphasic nociceptive behavior in the formalin test. Electroacupuncture enhanced the antinociceptive effect of intrathecal endomorphin-1 in the formalin test, resulting in a significant leftward shift in the dose-response curves for intrathecal endomorphin-1 antinociception. The enhanced effect was antagonized by intraperitoneal naltrexone. The study suggests that electroacupuncture may potentiate the intrathecal endomorphin-1 antinociception partially mediated by opioid receptors.
