D-Ala2-met-enkephalinamide (DAMEA) in ethyl urethane anesthetised rats increased the blood pressure, decreased heart rate and frequency of respirations. DAMEA could act centrally as well as peripherally after the penetration from the cerebro-spinal into the blood stream. These effects were blocked by naloxone. 6-Hydroxydopamine inhibited the circulatory and respiratory action of DAMEA. 5,6-Dihydroxytryptamine reversed this action of DAMEA. It is suggested that central presynaptic catecholamine and serotonin neurons modulate the central effects of DAMEA on the circulatory system and respiration in rats.