The somatic and visceral noxious stimuli could simultaneously induce the increase of discharges of pain-excitation neurons (PEN) and the decrease of discharges of pain-inhibition neurons (PIN) in the Nucleus Ventralis posterolalis (VPL) of thalamus in the rat, and the electric activities of the two kinds of neurons cooperated each other. By the injection of morphine (5 mg/kg) and the electroacupuncture of "zusanli", the discharges of PEN were reduced and the discharges of PIN were enhanced. The results suggested that VPL of thalamus in the rat be involved in the modulating action on pain sensation and the analgesic effects of morphine and electroacupuncture by the simultaneous electric activities of PEN and PIN in VPL.