Abstract
The involvement of endogenous morphine like factors in production of acupuncture analgesia (AA) caused by low frequency stimulation of the acupuncture point had been suggested by the fact that AA was antagonized by naloxone. Among of many kinds of the endogenous morphine like factors, the involvement of β-endorphin in AA have been investigated in present experiment by the intraventricular (3rd ventricle) application of anti-serum of β-endorphin. Pain threshold was measured by the tail flick test of the rats, and analgesia was expressed by percent changes of the tail flick latency. AA was completely abolished by intraventricular application of anti-serum of β-endorphin. Morphine analgesia (MA) caused by intraperitoneal 0.5mg/kg morphine, which is equivalent to AA, was also abolished by anti-serum of β-endorphin. Analgesia produced by electrical stimulation of the dorsal part of the peri-aqueductal central gray (D-PAG) or of the part of the anterior hypothalamus (AH2), which was identified as the part of the acupuncture afferent pathway from the acupuncture point to the hypophysis, was also abolished completely by anti-serum of the, β-endorphin. Analgesia was not produced by stimulation of the preoptic nucleus or of the median eminence, which was known as the reqions connected to the hypophysis. From these results, it was concluded that β-endorphin might involve in production of AA, and intraperitoneal 0.5mg/kg morphine analgesia. The sites of involvement of β-endorphin in production of such analgesias was still unknown, although stimulation-produced-analgesia in the AH2 which had been found as the final region to the hypophysis, was abolished by anti-serum of the β-endorphin.
