title: Inhibition of 5-hydroxytryptamine-potentiated aggregation of human blood platelets by 5-hydroxytryptamine receptor-blocking agents.
abstract: Blood platelets possess specific receptors for 5-hydroxytryptamine (5-HT) which differ from the carrier for the amine uptake. Activation of 5-HT receptors causes shape change and aggregation of platelets. We studied the influence of drugs with 5-HT receptor blocking properties on 5-HT-potentiated, ADP-induced aggregation of human blood platelets. The synergistic effect of 5-HT on aggregation was inhibited by the compounds tested in the order of potency: cyproheptadine, pizotifen, spiperone, methysergide, methiothepine , mianserin, ketanserin, dihydroergotamine. The IC50 values lay in the range from 14 to 40 nmol/l. Chlorpromazine and haloperidol were less effective by more than one order of magnitude. Our results indicate a certain similarity between the 5-HT receptors on platelets and the 5-HT receptors on serotonergic neurons and vascular smooth muscle which belong to the 5-HT2 receptor type.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology*; D004357:Drug Synergism; D006801:Humans; D007700:Kinetics; D008803:Mianserin / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology*
chemical_list: D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D008803:Mianserin; D012701:Serotonin; D000244:Adenosine Diphosphate