It has been reported that the effect of acupuncture analgesia could be decreased by the lesion of the caudate nucleus and increased by the stimulation of the same nucleus. Some transmitters in the caudate nucleus are involved in acupuncture analgesia, for example, opiates. The present experiment aimed to investigate which kinds of receptors were associated with acupuncture analgesia by means of microinjection of receptor antagonists into the caudate nucleus. The experiments were performed on Wistar rats of both sexes weighing 250-320g. The nociceptive responses of the left thalamic parafascicular nuclei were recorded with g1ass microelectrodes. A pair of stainless steel electrodes was inserted into the right foot of the rat for delivering noxious stimulation (5mA, 0.2ms, l00Hz, and 50ms). The rat received electroacupuncture at Zusanli (ST36) and Huamiao (GB30) points (l5-l8v for 3min, followed by l8-20v for 2min, l00Hz). After microinjection of naloxone (opioid receptor antagonist), β -FNA (opioid P receptor antagonist),ICIl74864 (opioid receptor antagonist), nor-BNI (opioid k receptor antagoniSt) into the caudate nuclei, the effects of electroacupuncture on nociceptive responses of the parafascicular nuclei were compared with the saline group. After microinjection of naloxone (n=9), D -FNA (n=9) respectively, the inhibition of electroacupuncture on nociceptive responses of the parafascicular nuclei was not observed. (P>0.05) Compared with the saline group, the inhibition was observed from 0min to 8min after stopping electroacupuncture, the differences were significant (P0.05). From these results it is suggested that opioid µ receptors but not opioid o,k receptors in caudate nuclei are involved in acupuncture analgesia.

Wu Guoji & Chen Zhengqiu.