In our previous studies, an insulin-dependent hypoglycemic effect produced by electroacupuncture (EA) was shown to be mediated by
endogenous opioid peptides (EOP). In the present study, we applied 2Hz EA to both zusanli acupoints (ST36) in the test group for 30 min, and
to a nonacupoint area in the control group for 30 min to compare the acupoint specific character in the hypoglycemic effect of EA. Assays of
plasma -endorphin and insulin levels were performed by ELISA kits. The insulin-dependent mechanism of the hypoglycemic effect was also
investigated in streptozotocin (STZ)-induced diabetic rats. The mediation of EOP and the role of -opioid receptor were examined by naloxone
and -opioid receptor knockout mice (MOR-KOM). The serotonin depletionwas carried out by injecting (i.p.) p-chlorophenylalanine (PCPA);
two low doses of serotonin were also injected (i.v.) to analyze the direct effect on plasma glucose levels. The hypoglycemic effect of EA
was much greater in rats stimulated at ST36 than in rats receiving the same stimulation at the nonacupoint area. The plasma levels of insulin
and -endorphin were also significantly elevated after stimulation of both zusanli acupoints, but remained unchanged following stimulation
at the nonacupoint area. There was no sharp hypoglycemic response to 2Hz EA at zusanli acupoint of STZ-induced diabetic rats. However,
the hypoglycemic effect of this EA was not totally blocked by the sufficient dose of naloxone (1 mg/kg, i.v.). Additionally, 2 Hz EA at ST36
also showed a sharp decrease in plasma glucose levels of MOR-KOM. Pretreatment with PCPA did not reproduce hypoglycemic response to
2Hz EA in naloxone-treated rats and MOR-KOM mice. Furthermore, injection of serotonin decreased the plasma glucose levels significantly.
Therefore, we suggest that serotonin also involved in the hypoglycemic action of 2Hz EA at both zusanli acupoints of normal rats.
