Effect of hypothalamic supraoptic nucleus on acupuncture analgesia in the rat

Hypothalamic supraoptic nucleus (SON) has been demonstrated to involve in pain modulation. Acupuncture analgesia is a very useful clinical skill for pain relief, which has over 2500-year history in China. The present study investigated the effect of SON on acupuncture analgesia in the rat. Electrical stimulation of the SON or microinjection of a small dose l-glutamate sodium into the SON enhanced acupuncture analgesia in a dose-dependent manner, while cauterization of the SON weakened acupuncture analgesia. Pituitary removal did not influence the effect of l-glutamate sodium that enhanced acupuncture analgesia in the SON. The data suggested that the neurons and not the nerve fibers in the SON played an important role in acupuncture analgesia, which effect might be through the central nervous system rather than the hypothalamo-neurohypophyseal system.