Large and small vessel responses to serotonin in the peripheral circulation

Serotonin normally constricts most large arteries and, in most vascular beds, dilates the arterioles. In the normal limb, the net result is an increase in blood flow. In two situations potentially relevant to peripheral vascular disease, the constrictor response to serotonin is enhanced and serotonin reduces limb blood flow. Potentiation of constrictor responses to serotonin, reversed by the 5-HT2 blocker ketanserin, occurs both in the arterial collateral circulation after femoral artery ligation and in the femoral artery after intimal damage. The potentiation appears to be specific for serotonin: in neither case is the response to norepinephrine enhanced. The observations in models provide a conceptual basis for preliminary observations, which indicate that ketanserin is effective in reversing symptoms in some patients with peripheral vascular disease.