Effects of histamine receptor antagonism on adrenaline-induced changes in blood pressure in intact dogs.
This study was designed to test the hypothesis that histamine may contribute to the vasodepressor response which occurs in response to physiologic increments in adrenaline concentration in intact animals. Accordingly, following a control period of 30 min, adrenaline was infused intravenously for 45 min at a rate of 250 ng/kg per min in 14 anaesthetized dogs (Group I). A second group of eight dogs received an identical adrenaline infusion following complete H1- and H2-histamine receptor antagonism with tripelennamine plus cimetidine (Group II). A time control group of experiments, in which no drugs were infused, as well as groups receiving adrenaline plus either tripelennamine or cimetidine, were also performed. In Group I, adrenaline infusion increased heart rate and reduced mean arterial blood pressure by 10 mmHg (P less than 0.01). Following combined H1- and H2-histamine receptor antagonism (Group II), adrenaline infusion failed to reduce mean arterial blood pressure. However, mean arterial blood pressure was reduced significantly in the groups receiving adrenaline plus only one of the histamine receptor blocking agents. Since only the combined histamine receptor blockade completely eliminated the vasodepressor response to adrenaline, the data suggest that histamine may play a physiological role in the vasodepressor response to circulating adrenaline in the intact animal, and that both H1- and H2-histamine receptors may be involved.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002927:Cimetidine / Q000494:pharmacology*; D004285:Dogs; D004837:Epinephrine / Q000097:blood / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D014309:Tripelennamine / Q000494:pharmacology*
D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D014309:Tripelennamine; D002927:Cimetidine; D004837:Epinephrine