Endomorphin and mu-opioid receptors in mouse brain mediate the analgesic effect induced by 2 Hz but not 100 Hz electroacupuncture stimulation.
This work was designed to examine whether brain endomorphins (EM1 and EM2), the endogenous mu-opioid ligands, are involved in electroacupuncture (EA)-induced analgesia in the mice. C57BL/6J mice were given EA for 30 min and the effect of EA-induced analgesia was assessed by radiant heat tail flick latency (TFL). Intracerebroventricular (i.c.v.) injection of mu-opioid receptor antagonist D-Phe-Cys-Tyr-D-Tyr-Orn-Thr-Pen-Thr-NH(2) (CTOP), or antiserum against EM1 or EM2 was performed to see whether EA analgesia could be blocked. The results showed that: (1) i.c.v. injection of CTOP at 25-100 ng dose-dependently antagonized the analgesia induced by EA of 2 Hz, but not 100 Hz. (2) Intracerebroventricular injection of EM1 antiserum (5 ml, 1:1 or 1:10 dilution) dose-dependently antagonized 2 Hz, but not 100 Hz EA analgesia. (3) EM2 antiserum showed similar effect at 1:1 dilution. The results are interpreted to mean that endogenously released EM1 and EM2 and the cerebral mu-receptors are involved in mediating 2 Hz but not 100 Hz EA analgesia in the mice.
Huang
C
C
Neuroscience Research Institute, Peking University, 38 Xue Yuan Road, 100083, PR, Beijing, China.
Wang
Y
Y
Chang
J K
JK
Han
J S
JS
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology; D015671:Electroacupuncture / Q000379:methods; D005260:Female; D007106:Immune Sera / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D010147:Pain Measurement / Q000187:drug effects*; D017450:Receptors, Opioid, mu / Q000187:drug effects; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000494:pharmacology
D007106:Immune Sera; D009842:Oligopeptides; D017450:Receptors, Opioid, mu; C105293:endomorphin 1; C049352:phenylalanyl-cyclo(cysteinyltyrosyl-tryptophyl-ornithyl-threonyl-penicillamine)threoninamide; C105294:endomorphin 2; D013004:Somatostatin