The evidence for histamine H_3 receptor-mediated endothelium-dependent relaxation in isolated rat aorta

• Published in: Mediators of Inflammation 1995-12, Vol.1995 (3), p.217-221
• Main Authors: Djuric, D. M., Andjelkovic, I. Z.
• Format: Article
• Language: English
• ISSN: 0962-9351; 1466-1861
• DOI: 10.1155/S0962935195000354

THE presence of histamine H_3 receptors was evaluated on the rat aorta endothelium. In the presence of pyrilamine (1 nM, 7 nM, 10 nM) or thioperamide (1 nM, 10 nM, 30 nM) the concentration–response curve for histamine-induced (0.1 nM - 0.01 mM) endothelium-dependent rat aorta relaxation was shifted to the right without significant change of the Emax indicating competitive antagonism by pyrilamine (pA_2= 9.33 ± 0.34, slope = 1.09 ± 0.36) or thioperamide (pA_2=9.31 ± 0.16, slope=0.94 ± 0.10). Cimetidine (1 μM) did not influence histamine-induced endothelium-dependent rat aorta relaxation. In the presence of thioperamide (1 nM, 10 nM, 30 nM) the concentration–response curve for (R)α-MeHA-induced (0.1 nM - 0.01 mM) endothelium-dependent relaxation was shifted to the right without significant change of Emax indicated competitive antagonism by thioperamide (pA_2 = 9.21 ± 0.4, slope = 1.03 ± 0.35). Pyrilamine (100 nM) or cimetidine (1 μM) did not influence (R)α-MeHA-induced endothelium-dependent rat aorta relaxation. These results suggest the presence of a heterogenous population of histamine receptors, H1 and H3, on rat aorta endothelium.