Beta-endorphin. Vasodilating effect on the microcirculatory system of hamster cheek pouch

beta-Endorphin, enkephalins and morphine dilated in vivo the arteriole of the microcirculatory system in hamster cheek pouch. beta-Endorphin had the highest potency and morphine the lowest. The effect was dose dependent and blocked competitively by the opiate antagonist, naloxone. The result demonstrated an effect of the opiates on the arteriole of the cutaneous circulation. This effect probably plays an important role in thermoregulation.