Responses of isolated canine basilar artery and human platelet to chlorpromazine and amitriptyline.

Sustained contraction of isolated canine basilar artery was induced by addition of prostaglandin F2 alpha, prostaglandin E2, hemoglobin-containing solution, or serum. Human platelet aggregation was induced by 1.0 microM adenosine diphosphate. The sustained contraction of basilar artery and the aggregation of platelet, particularly its secondary aggregation, were inhibited in a dose-dependent manner by addition of chlorpromazine or amitriptyline; calmodulin antagonist. The molar concentrations at 50% inhibition by chlorpromazine or amitriptyline were 5.9 to 7.7 microM or 28 to 39 microM for the contraction of basilar artery and 57 microM or 111 microM for the secondary aggregation of platelet. The results were discussed mainly on the basis of interaction of psychotropic drugs and Ca2+, calmodulin-dependent enzymes, particularly myosin light chain phosphorylation.