A rise or a fall in systemic blood pressure brought about by the I.V. infusion of peripherally acting drugs (adenosine, noradrenaline or methoxamine) inhibited shivering in the cold-exposed rat. 2. Since the injection of commonly used doses of noradrenaline (0.05-0.10 mumole) into a lateral cerebral ventricle of a rat was usually accompanied by a rise in blood pressure special precautious were required to determine whether noradrenaline had a specific central effect on shivering. 3. Small doses of noradrenaline (0.02-0.03 mumole) or clonidine (0.01 mumole) which had no effect on blood pressure when injected into a lateral cerebral ventricle still inhibited shivering in the cold-exposed rat and this effect was prevented by phentolamine. 4. It is concluded that noradrenaline can inhibit the cold sensor-shivering pathway in its central course by an action on alpha-receptors.
