Involvement of serotonin in the hypoglycemic response to 2 Hz electroacupuncture of zusanli acupoint (ST36) in rats.
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 2 Hz 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 beta-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 mu-opioid receptor were examined by naloxone and mu-opioid receptor knockout mice (MOR-KOM). The serotonin depletion was 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 beta-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 2 Hz 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 2 Hz 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 2 Hz EA at both zusanli acupoints of normal rats.
Chang
Shih-Liang
SL
Graduate Institute of Integration Chinese and Western Medicine, China Medical University, Taichung, Taiwan, ROC. slchang@mail.cmu.edu.tw
Tsai
Chin-Chuan
CC
Lin
Jaung-Geng
JG
Hsieh
Ching-Liang
CL
Lin
Rong-Tsung
RT
Cheng
Juei-Tang
JT
D015669:Acupuncture Points; D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000187:drug effects / Q000528:radiation effects; D004347:Drug Interactions; D015671:Electroacupuncture / Q000379:methods*; D005215:Fasting / Q000502:physiology; D010134:Fenclonine / Q000494:pharmacology; D007003:Hypoglycemia / Q000139:chemically induced / Q000378:metabolism / Q000628:therapy*; D007328:Insulin / Q000097:blood; D008297:Male; D051379:Mice; D018345:Mice, Knockout / Q000502:physiology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D051381:Rats; D017450:Receptors, Opioid, mu / Q000172:deficiency; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013311:Streptozocin; D001615:beta-Endorphin / Q000097:blood
D001786:Blood Glucose; D007328:Insulin; D009292:Narcotic Antagonists; D017450:Receptors, Opioid, mu; D012702:Serotonin Antagonists; D012701:Serotonin; D009270:Naloxone; D013311:Streptozocin; D001615:beta-Endorphin; D010134:Fenclonine