title: Histamine H2 receptor-mediated endothelium-dependent relaxation in canine spinal artery.
abstract: The mechanisms of histamine-induced relaxation were investigated in isolated canine spinal branches of intercostal artery (SBICA). Histamine (10(-7) to 10(-4)M) and dimaprit (3 x 10(-6) to 3 x 10(-4)M) produced concentration-dependent relaxation in the SBICA which had been contracted by 5 x 10(-6)M norepinephrine, whereas 2-pyridylethylamine caused only a very small relaxation. The histamine- and dimaprit-induced relaxation were inhibited by famotidine but not by diphenhydramine. In the SBICA without endothelium, histamine elicited very little relaxation. Aspirin (5 x 10(-5)M) and AA 861 (10(-5)M) did not affect the histamine-induced relaxation. Treatment with L-NMMA (3 x 10(-5)M) or methylene blue (10(-5)M) significantly suppressed the acetylcholine-induced relaxation of the SBICA but not the histamine-induced one. These results suggest that histamine produces relaxation in the isolated canine SBICA through stimulation of H2-receptors on the endothelium. The relaxing mediator(s) released by histamine seems to be neither endogenous prostaglandins, lipoxygenase products, nor nitric oxide.
mesh_terms: D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D017259:Dimaprit / Q000494:pharmacology; D004285:Dogs; D004730:Endothelium, Vascular / Q000502:physiology*; D005260:Female; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D011970:Receptors, Histamine H2 / Q000502:physiology*; D013116:Spinal Cord / Q000098:blood supply*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D011970:Receptors, Histamine H2; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D006632:Histamine; D017259:Dimaprit