Characterization of histamine-induced relaxation in pre-contracted rat aorta

Abstract

Histamine is one of many neurotransmitters that have been implicated in cardiovascular functioning. Three subtypes of histamine receptors (H1, H2 and H3) have been identified in the different blood vessels of some animal species [1]. Accordingly, several studies showed in vitro differences of histamine vasomotor effects depending on the animal species, vessel type or vascular bed used in the experiments [2]. In the rat isolated aorta the involvement of H1 and H2 receptors in the vasorelaxation response have been shown [1, 3, 4]. However, the role of H3 receptors in the vasomotor responsiveness remains to be elucidated [5]. Thus, the complexity of vascular responses to histamine, based on its action on histaminergic receptor subtypes, was re-evaluated using similar experimental protocols. The aim of the study was to evaluate the effect of selective histamine H1, H2 and H3 receptor antagonists [6] on histamine induced relaxation of noradrenaline pre-contracted rat isolated aortic rings.