Evidence for functional 5-HT2 receptor sites on human blood platelets.

The aggregation of normal human platelets by 5-hydroxytryptamine (5-HT) is the result of a specific interaction of the monoamine with a platelet receptor since it is not influenced by adrenergic receptor blockade, inhibition of fatty acid cyclo-oxygenase or ADP-scavenging. The 5-HT induced platelet reaction is inhibited in a concentration-dependent way by various serotonergic antagonists; the potency of these compounds in this respect correlates strongly with their potential to inhibit the specific binding of [3H] ketanserin, a selective label for 5-HT2 binding sites, to rat prefrontal cortex and striatum and to cat platelet membranes. This study thus provides evidence for a functional role as true receptor initiating a physiological response of the 5-HT2 receptor on human platelets.