Cold-induced potentiation of alpha 2-adrenergic vasoconstriction in primary Raynaud's disease

To determine the effects of local cooling on alpha-adrenergic responses in the fingers of patients with idiopathic Raynaud's disease. Clonidine HCl and phenylephrine HCl were administered through a brachial artery catheter while blood flow was measured by plethysmography in cooled and uncooled fingers. Cooling potentiated alpha 2-adrenergic vasoconstriction in the patients but depressed this response in the controls. Vasoconstrictive responses to phenylephrine were not significantly affected by cooling but were significantly greater in the patients than in the controls. Cold-induced sensitization of peripheral vascular alpha 2-adrenoceptors may be involved in the mechanism by which cooling triggers the vasospastic attacks of Raynaud's disease.