Potentiation of norepinephrine on rat acupuncture analgesia antagonized by arcuate nucleus lesion or naloxone blockeci on opiate receptors in periaqueductal gray

Previously we found that injection of norepinephrine 3 Ug (3 U1) in 2 min into the ventromedial hypothajamic nucleus in rats markedly potentiated the analgesic effect of electroacupuncture. The potentiation, in this experiment. was blocked by injection of naloxone 0.4 vg cirri) in 1 min into the ventromedial periaqueductal gray. Lesion of the arcuate nucleus with ip mono-sodium glutamate 2 g/(kg-d) x 5 not only abolished the effect of norepinephrine, but also reduced the content of leunkephalin in the hypothalamus central gray and pituitary gland (p<0.01). These results indicated that opiate neurons in the arcuate nucleus and opiate receptors in ventromedial periaqueductal gray were involved in the potentiation of analgesic effect of electroacupuncture produced by norepinephrine.