Effects of cyclooxygenase inhibition on vascular responses evoked in fingers of men and women by iontophoresis of α 1 ‐ and α 2 ‐adrenoceptor agonists

Non‐technical summary  Sympathetic nerve fibres in the fingers release noradrenaline, which has the potential to act on α 1 ‐ or α 2 ‐adrenoreceptors on the blood vessels. We used iontophoresis, which generates a tiny electrical charge, to push selective α 1 ‐ or α 2 ‐receptor agonists through the skin and recorded changes in finger blood flow before and after aspirin, which inhibits cyclooxygenase (COX), an enzyme which synthesises vasodilator and vasoconstrictor prostaglandins. Our results yielded the novel findings that finger vasoconstriction produced by α 1 ‐adrenoceptors is blunted by locally synthesised vasodilator COX products in young men and in young women in the high but not the low oestrogen phase of the menstrual cycle. By contrast, finger vasoconstriction evoked by α 2 ‐adrenoceptors is largely attributable to vasoconstrictor COX products in young men, but overcome by vasodilator COX products in young women. This provides a foundation for testing whether COX products similarly modify vasoconstriction evoked by changes in sympathetic nerve activity.