GENDER DIFFERENCES IN MODULATION OF PERIPHERAL VASCULAR ADRENOCEPTORS

We have previously demonstrated that women have smaller digital vasoco nstrictive responses to intra-arterial phenylephrine and clonidine tha n men. Subsequent research suggested that women have higher levels of peripheral vascular sympathetic tone than men. We therefore sought to determine if reducing sympathetic tone by reflex heating would affect the sex difference in peripheral vascular cr-adrenergic responsiveness . Twenty-two normal male and 21 normal female volunteers were studied during either heated or unheated conditions while phenylephrine HCL an d clonidine HCL were infused through a brachial artery catheter. Pheny lephrine caused greater vasoconstriction in men than in women which wa s unaffected by heating. Clonidine also caused significantly greater v asoconstriction in men than in women. However, heating significantly i ncreased clonidine-induced vasoconstriction in women but not in men. T hese data suggest that reduction of sympathetic tone elevates peripher al vascular alpha(2)-adrenergic sensitivity in women; this effect does not occur in men.