MODIFICATION OF CARDIOVASCULAR RESPONSES TO HISTAMINE BY DITHIOTHREITOL

Abstract

1Histamine produced dose-dependent contractile responses on both isolated perfused ear arteries and aortic strips of the rabbit. These responses were blocked by mepyramine and potentiated by both metiamide and dithiothreitol. 2In the presence of maximum potentiation by metiamide, dithiothreitol still potentiated the contractile response to histamine of both preparations. 3In the presence of mepyramine, histamine produced dose-dependent reductions in the contractile response to noradrenaline. This vasodilator action of histamine was abolished by metiamide but was unaffected by dithiothreitol. 4The vasodilator action of histamine on the human isolated perfused temporal artery and the positive inotropic effect of histamine on the isolated spontaneously beating atria of the rabbit were blocked by metiamide but unaffected by dithiothreitol. 5It is concluded that the rabbit aorta, like the ear artery, contains both H₁ and H₂ histamine receptors and that dithiothreitol potentiates cardiovascular responses mediated by H₁-receptors but not by H₂-receptors.