Résumé
Histamine can stimulate the heart by directly interacting with cardiac histamine receptors. In the present study we have investigated the H[2] receptor activity in isolated rabbit heart. Cimetidine, a specific H[2] receptor antagonist was used. The isolated heart was mounted in langendroff apparatus. The heart was perfused at a constant pressure with oxygenated Ringer's Locke solution. H[2] receptor antagonist produces negative inotropic effect in the presence of histamine. This indicates that H[2] receptors are present in rabbit heart, and plays a role in mediation of positive inotropic effect produced through CAMP by histamine
Sujets)
Animaux de laboratoire , Antihistaminiques des récepteurs H2 , Cimétidine/pharmacologie , Histamine/pharmacologie , Lapins , CoeurRésumé
There is no doubt that the effects of the catecholamines of the heart are mainly due to the stimulation of beta-adrenoceptors but in the mid 1960' s the first evidence was presented that a-adrenoceptors mediating positive inotrpoism exists also in the myocardium beside well established beta -adrenoceptors. In our observation adrenaline shows a positive inotropic response. The response of adrenaline in presence of metoprolol [beta1blocker] showed negative inotropic effect