title: Verapamil, an antagonist at 5-hydroxytryptamine receptors of human blood platelets.
abstract: In human blood platelets verapamil and D600 (2-methoxyverapamil) in therapeutic concentrations inhibited the shape change reaction induced by 5-hydroxytryptamine (5HT) but not that induced by ADP. The N-methylated derivatives (D575 and D890) had much less effect. The inhibitory action of verapamil was independent of external Ca2+. Nitrendipine and diltiazem (20 microM) had no effect on the 5HT- and the ADP-induced shape change reactions. Since both these shape change reactions are mediated by a rise in cytoplasmic free Ca2+, it is concluded that the inhibition of the 5HT effect by verapamil and D600 was not due to their interference with calcium channels but rather to an antagonistic action on 5HT2-receptors. This view is supported by the finding that verapamil but not D575 competed with [3H]ketanserin and [3H]spiroperidol for their specific binding sites on membranes of rat cerebral cortex.
authors.forename: H
authors.initials: H
authors.lastname: Affolter
authors.forename: W P
authors.initials: WP
authors.lastname: Burkard
authors.forename: A
authors.initials: A
authors.lastname: Pletscher
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D001667:Binding, Competitive; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D002540:Cerebral Cortex / Q000378:metabolism; D005711:Gallopamil / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007650:Ketanserin; D008566:Membranes / Q000378:metabolism; D010880:Piperidines / Q000378:metabolism; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000378:metabolism; D013134:Spiperone / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D010880:Piperidines; D011985:Receptors, Serotonin; D005711:Gallopamil; D013134:Spiperone; D000244:Adenosine Diphosphate; D007650:Ketanserin; D014700:Verapamil