Serotonin and preactivated platelets in essential hypertension.

In patients with essential hypertension, an activated platelet serotonin-induced vasoconstrictor axis can be postulated. Platelets from hypertensive patients have a shortened half-life, and turnover of serotonin is increased. Vasoconstriction may be produced through activation of 5-HT2 receptors secondary to high wall concentrations of serotonin released from "activated" platelets. The pharmacotherapeutic relevance of this pathophysiological chain of events can be tested with the 5-HT2-receptor blocker ketanserin, but the drug's alpha 1-blocking activity has to be taken into account. Ketanserin lowers blood pressure effectively and to a greater extent in older patients. This points to an age-linked mode of action, possibly related to greater endothelial and blood vessel damage with older age.