The effect of histamine on the tonus of isolated coronary arteries with intact and damaged endothelium

: In isolated rings of the pig coronary arteries mechanical damage of endothelium led to a considerable reduction of coronary spastic responses to histamine due to the H1-receptors damage after the denudation of endothelium. The tachyphylaxis to histamine was eliminated after de-endothelialization. The drugs blocking H1-receptors such as dimedrol, were effective for preventing the histamine coronary vasospasm.