Effect of histamine on human placental chorionic veins: interaction with serotonin.
The vasomotor effects of histamine and its interaction with serotonin were studied in isolated human placental chorionic veins. Histamine induced concentration-dependent contractions with an EC50 of 8.7 +/- 1.2 x 10(-6) mol/l. The H1 antagonist, pyrilamine (10(-9) to 10(-7) mol/l), inhibited histamine-induced contractions, with a pA2 of 8.33 +/- 0.32 at a slope of 0.635. Cimetidine (H2 antagonist) had no effect on histamine-induced contractions. Serotonin (10(-9) to 10(-8) mol/l) significantly potentiated the contractile effect of histamine. The possible implications of the interaction between both amines in the regulation of placental blood flow is discussed.