Electrical and local chemical stimulation of the n. cuneiformis, the parabrachial medial nucleus, the n. raphe median and the n. raphe magnus induces an inhibition of locomotor activity in rats. Changes of the legs' flexor and extensor muscles' tone followed electrical stimulation of the inhibitory zones. Lesion of the n. n. median and magnus raphe blocks the inhibitory effects of electrical stimulation of the n. cuneiformis and the parabrachial medial nucleus.