is coffee a vasodilator in the brain
is caffeine a vasoconstrictor or a vasodilator? Answers: vasoconstrictor. vasoconstritor and a diuretic. Caffeine is also a known competitive inhibitor of the enzyme cAMP-phosphodiesterase (cAMP-PDE), which converts cyclic AMP (cAMP) in cells to its noncyclic form, allowing cAMP to build up in cells.