Selectivity of calcium antagonism and serotonin antagonism with respect to venous and arterial tissues.

There are marked differences in responsiveness to naturally occurring vasoactive substances1-4 between isolated blood vessels of different anatomical origin and in particular between arteries and veins. This discussion will deal with two major aspects where arterial and venous smooth muscle differ in their sensitivity to vasoactive agents; their sensitivity to inhibitors of calcium-influx (Ca2+ antagonists) on the one hand and their reactivity to serotonin (5-hydroxytryptamine) and serotonin antagonists, on the other.