ATTENUATION OF MORPHINE ANALGESIA BY PARTIAL LESION OF PERIAQUEDUCTAL CENTRAL GRAY

Abstract

Insertion of electrode (0.4mm in diameter) into periaqueduct central gray abolished acupuncture analgesia which was measured by tail-flick latency of rats, and also extremely reduced morphine analgesia which was induced by intraperitoneally injected 0.5mg/kg morphine.
Stimulation-produced analgesia which was induced by electric current applied to the limited periaqueduct central gray region and which was slightly intense than acupuncture analgesia was abolished by intraperitoneally injected 1.0mg/kg naloxone.
Since it was reported that acupuncture analgesia was antagonized by naloxone, these data indicate that periaqueduct central gray and endogenous morphine like factors involved in acupuncture analgesia.