ABSTRACT
The present study was to investigate whether entopeduncular nucleus (EP) is involved in caudate-putamen nucleus (CPu) stimulation-induced analgesia and in acupuncture analgesia. It was found that the foot-withdrawal latency elicited by radiant heat exposure was increased after electroacupuncture analgesia (EA), and the nociceptive responses of neurons in parafascicular nucleus (Pf) were inhibited after EA or after excitation of CPu neurons in normal rats, but the foot-withdrawal latency and nociceptive responses of Pf neurons were unchanged by EA or excitation of CPu in the rats with lesion of EP by local application of kainic acid. The results obtained with microinjeciton of saline instead of kainic acid into the EP were the same with those in the nonlesioned control group. The differences in the results between the lesion group and the other groups were significant ( <0.05). It is suggested that EP is involved in acupuncture analgesia and also plays an important role in caudate-putamen nucleus stimulation-induced analgesia.