Zhen Ci Yan Jiu. 1990 ; 15(2): 97-103.

[Influence of microinjection of dynorphin antibody into periaqueductal gray (PAG) on analgesia induced by electroacupuncture of different frequencies in rats]

He C, Han J.

Department of Physiology, Beijing Medical University.

Previous studies have shown that 2 Hz but not 100 Hz electroacupuncture (EA) stimulation released beta-endorphin in PAG of the rat to induce analgesia. The present study was undertaken to see whether dynorphin plays a role in PAG in mediating analgesia induced by low and high frequency EA. Injection of affinity purified dynorphin antibody (1:350,000 in RIA titer) 1 microliter into PAG blocked 2 Hz EA analgesia almost completely, and 15 Hz EA analgesia partly, leaving 100 Hz EA analgesia intact. This blocking effect was totally disappeared when the antibody was diluted to 1/10 of its original concentration (1:35,000). Besides, injection of dynorphin into PAG through chronically implanted cannula showed no analgesic effect. The results suggest that the blockade of 2 Hz EA analgesia by high titer dynorphin antibody injected into PAG may have been the result of cross reactivity of the antibody to other opioid peptides (such as beta-endorphin, enkephalin, etc) released in the PAG area. The data also stress the importance of using antibodies of proper titer and concentration to exclude false positive or false negative conclusions in adopting the antibody microinjection techniques, as was repeatedly shown in the immunohistochemical studies.