Thermoregulatory effects of D-met2-pro5-enkephalinamide.

Changes elicited in the body temperature by subcutaneous injection of the synthetic D-met2-pro5-enkephalinamide (D-met2-pro5-EA) were studied in CFY rats. D-met2-pro5-EA in doses of 8, 20 and 40 mg/kg caused hyperthermia. If the animals were restrained, this hyperthermic effect was attenuated. Ten mg/kg naloxone completely prevented the elevation of body temperature. Previous administration of 300 mg/kg capsaicin in fractionated daily doses resulted in a facilitation of the hyperthermic reaction. In contrast to other opioids, hypothermia was never observed. Our observations support the concept of multiple opiate-sensitive mechanisms in thermoregulation.