Double action of nicardipine on serotonin release from rat platelets.
We studied the effect of nicardipine on the release of preincorporated tritiated serotonin (5-HT) from washed rat platelets and on platelet 5-HT uptake. Nicardipine exerted a complex action. It partially antagonized thrombin-induced 5-HT secretion, but also induced the "selective" release of 5-HT without concomitant ATP release in the absence of platelet activation and inhibited active 5-HT uptake. The two latter effects were observed in the presence of EGTA and therefore could not be related to calcium channel blockade. Verapamil, TMB 8, and the calmodulin antagonists trifluoperazine and R 24571 also possessed this multiplicity of action; however, verapamil and TMB 8 were weaker inducers of selective 5-HT release and uptake inhibition. These results show that, in addition to its inhibitory effect on thrombin-induced platelet activation, nicardipine inhibits platelet 5-HT accumulation. Its administration may therefore result in 5-HT depletion.
D000818:Animals; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D009529:Nicardipine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000378:metabolism*; D013917:Thrombin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D012701:Serotonin; D009529:Nicardipine; D013917:Thrombin