Noxious electric stimulation may release sympathetic mediators, since subcutaneously administered propranolol inhibited a peripheral analgesic effect by decreasing the vocalizing response of conscious guinea pigs to electric stimulation. Local injection of noradrenaline and isoprenaline induced increased vocalization to stimulation. Propranolol inhibited the effect of noradrenaline. The activation of beta-adrenergic receptors may participate in peripheral nociceptive information.