title: Vascular responses of the isolated perfused stomach of rabbit and rat to histamine.
abstract: Gastric vascular responses to histamine and its selective H1- and H2-agonists in vitro were investigated in the isolated vascular-perfused stomach of rabbit and rat. In the rabbit stomach under resting conditions bolus injection of histamine (5-80 nmol) caused a small increase in perfusion pressure (PP). However, during infusion of noradrenaline (1 microM), which elevated vascular tone, histamine (5-80 nmol) caused a dose-dependent biphasic vascular response, an initial increase followed by a fall in PP. Under similar conditions, the H1-agonist 2-pyridyl ethylamine, (2-PE; 50-400 nmol) elevated PP, whereas the H2-agonist dimaprit (80-640 nmol) reduced PP. The H1-antagonist mepyramine (0.25 microM) converted the biphasic response of histamine (5-50 nmol) to a monophasic vasodilation whereas the H2-receptor antagonist, cimetidine (1 microM) converted the biphasic response to a vasoconstriction. Similar responses were observed during conditions of elevated vascular tone induced by vasopressin or angiotensin II. In the rat stomach, histamine and both dimaprit and 2-PE reduced PP during conditions of elevated vascular tone. These findings support the presence of both H1- and H2 receptors in the gastric vasculature of both rat and rabbit; in both species, the H2-response is vasodilation whereas the nature of the H1-response is species dependent.
mesh_terms: D000818:Animals; D017259:Dimaprit; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011817:Rabbits; D051381:Rats; D011969:Receptors, Histamine H1 / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000502:physiology; D013045:Species Specificity; D013270:Stomach / Q000098:blood supply*; D013890:Thiourea / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D006633:Histamine Antagonists; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D014665:Vasodilator Agents; D006632:Histamine; D013890:Thiourea; D017259:Dimaprit