Changes of mu opioid receptor binding sites in rat brain following electroacupuncture.

With [3H]-ohmefentanyl as a ligand, autoradiographic technique was used to observe the effect of electroacupuncture (EA) on mu opioid receptor binding sites in the brain areas related to pain modulation. The results were as follows: (1) The distribution of the mu receptor in the rat central nervous system was consistent in general with the results reported previously. (2) After EA of Tsu-San-Li, the mu receptor binding sites were increased significantly in the following examined structures: the caudate nucleus, septal nucleus, medial preoptic area, amygdalaoid nucleus, periaqueducal gray, interpeduncular nucleus, nucleus raphe magnus, and cervical and lumbar enlargements. The results indicate that EA is able to increase mu binding sites in the brain areas related to analgesia, suggesting the enhancement of mu receptor function by EA.