Gender differences in modulation of peripheral vascular adrenoceptors

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System
• Pharmacology

Background:

• Previous studies show women have reduced digital vasoconstriction to phenylephrine and clonidine compared to men.
• Research indicates women may possess higher peripheral vascular sympathetic tone than men.

Purpose of the Study:

• To investigate if reducing sympathetic tone via reflex heating alters sex differences in peripheral vascular alpha-adrenergic responsiveness.
• To determine the impact of decreased sympathetic tone on phenylephrine and clonidine vasoconstrictive effects in men and women.

Main Methods:

• Twenty-two men and 21 women participated, studied under heated and unheated conditions.
• Phenylephrine hydrochloride and clonidine hydrochloride were infused intra-arterially via a brachial artery catheter.
• Digital vasoconstrictive responses were measured and compared between sexes and heating conditions.

Main Results:

• Phenylephrine induced greater vasoconstriction in men than women, an effect not altered by heating.
• Clonidine also caused significantly greater vasoconstriction in men compared to women.
• Reflex heating significantly enhanced clonidine-induced vasoconstriction in women, but not in men.

Conclusions:

• Reduced sympathetic tone selectively increases peripheral vascular alpha-2 adrenergic sensitivity in women.
• This suggests a sex-specific mechanism where sympathetic tone modulation impacts alpha-adrenergic receptor function differently between men and women.