Sheng Li Xue Bao. 1999 Feb; 51(1): 49-54.

[Opioid mu receptors in caudate nucleus contribute to electroacupuncture and Sm I generating inhibition on nociceptive responses of Pf neurons]

Wu GJ, Chen ZQ.

Institute of Acupuncture, China Academy of TCM, Beijing 100700.

The present experiments aimed to investigate whether the caudate nucleus (Cd) was involved in cortical sensorimotor area I (Sm I) generating descending modulation of the parafascicular nucleus (Pf) in acupuncture analgesia (AA), and what type of opiate receptors in Cd were involved. It was found that nociceptive responses of Pf neurons could be inhibited by electroacupuncture (EA) and excitation of Sm I before lesion of Cd, but not after lesion. After microinjection of naloxone beta-FNA, the specific antagonist for opioid mu receptors, into Cd,the inhibitory effect of EA or activation of Sm I on nociceptive responses of the Pf neurons was abolished, but it was not influenced by microinjection of nor-BNI and ICI174,864, the specific antagonists for opioid kappa and delta receptors, respectively. Together with our previous findings that EA could activate cortical neurons to participate in descending modulation of activities of Pf neurons, the present results suggest that Cd is associated with Sm I generating descending inhibition on nociceptive responses of Pf neurons in AA, and it is most likely that opiates in Cd may be involved in this inhibition through mu but not kappa or delta receptors.