We found that electroacupuncture (EA) at the Zhongwan acupoint released b-endorphin to induce an insulin-dependent
hypoglycemia in rats. The present study investigated the source of b-endorphin. EA at 2 Hz for 30 min in rats
decreased plasma glucose that could be abolished by naloxone. A similar effect of EA was also observed in wild-type
mice but disappeared in m-opioid receptor knockout mice. Mediation of the m1-opioid receptor is considered from the
blockade of response to EA by naloxonazine in rats. Otherwise, adrenalectomy abolished not only the hypoglycemic
response to EA in rat and mouse but also the increase of plasma b-endorphin and insulin by EA in rats. In conclusion, the
increase of plasma b-endorphin by EA at 2 Hz is mainly from the adrenal gland.
