Cyproheptadine and pizotifen inhibit serotonin-enhanced U46619-induced human platelet aggregation <i>in vitro</i>.

<p>(A) Human PRP was stimulated with submaximal concentration of U46619 (0.125 µM) in the presence or absence of serotonin (15 µM). (B) Human PRP was pre-incubated with increasing doses of cyproheptadine (0.1–250 nM) for 1 min and activated with U46619 (0.125 µM) and serotonin (15 µM). (C) Human PRP was pre-incubated with increasing doses of pizotifen (0.1–30 nM) for 1 min and activated with 0.125 µM U46619 and 15 µM serotonin. (D) Human PRP was pre-incubated with increasing doses of EMD 281014 (5–20 nM) for 1 min and activated with 0.125 µM U46619 and 15 µM serotonin. (E) Human PRP was pre-incubated for 1 min with the highest concentrations of cyproheptadine (250 nM), pizotifen (30 nM), and EMD 281014 (20 nM) used in this set of experiments, and activated with U46619 (0.125 µM). Inset shows quantification of the data. Each experiment was repeated at least 3 times, with blood obtained from three separate donors.