Effects of ketanserin,a selective 5-HT2 serotonergic antagonist,on the secondary recruitment of human plateletsin vitro

Ketanserin, a selective 5-HT₂ serotonergic receptor antagonist, reducesin vitro the release-associated human platelet aggregation induced by threshold concentrations of collagen and curtails the second wave of aggregation/release induced by critical concentrations of ADP in particular and, to a lesser extent, of 1-epinephrine. Its inhibitory effect on the second waves becomes more pronounced when the reaction is already attenuated by moderate cyclo-oxygenase inhibition with esculetin, by yohimbine or by propranolol. The first wave of aggregation induced by ADP or 1-epinephrine is not affected.Such an inhibition of secondary platelet recruitment by ketanserinin vitro may be due to an inhibition of the 5-HT₂ receptor-mediated amplifying effects of platelet-released 5-HT or to a non-specific interference with the platelet membrane, reducing the release of mediators from the platelets.Reduction of the increased plasma BTG levels in patients after ketanserin may result from such release-inhibiting mechanisms.