Experiments were carried out on conscious immobilized rats. Stimulation of the nucleus accumbens could strongly inhibit spontaneous as well as the nocicpeitve discharges of the lateral habenular nucleus units which were excited by noxious stimulation (LHPE). The inhibitory effect might be blocked by i.p. injection of naloxone (6 mg/kg). Electrical stimulation of the nucleus accumbens increased the frequency of spontaneous discharges of lateral habenular nucleus units which were inhibited by noxious stimulation (LHPI). Bilateral injection of naloxone (1.8 .mu.g) into the nucleus accumbens increased the frequency of spontaneous discharges of LHPE, but the spontaneous discharges of LHPE were abolished by injection of morphine (15 .mu.g) into bilateral nucleus accumbens. The results mentioned above and their significance in acupuncture analgesia were discussed.