Gender differences in modulation of peripheral vascular adrenoceptors

We have previously demonstrated that women have smaller digital vasoconstrictive responses to intra-arterial phenylephrine and clonidine than 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 α-adrenergic responsiveness. Twenty-two normal male and 21 normal female volunteers were studied during either heated or unhealed conditions while phenylephrine HCL and clonidine HCL were infused through a brachial artery catheter. Phenylephrine caused greater vasoconstriction in men than in women which was unaffected by heating. Clonidine also caused significantly greater vasoconstriction in men than in women. However, heating significantly increased clonidine-induced vasoconstriction in women but not in men. These data suggest that reduction of sympathetic tone elevates peripheral vascular α2-adrenergic sensitivity in women; this effect does not occur in men.