The possible involvement of hyperpolarizing mechanisms in histamine-induced relaxation of the rat portal vein.
The present study evaluated the effects of histamine 10(-2) M on longitudinal preparations of rat portal vein. It was observed that histamine 10(-2) M induced relaxation of rat portal vein preparations pre-contracted with phenylephrine 10(-4) M. On the other hand, no pharmacological effects were observed in preparations not pre-contracted. The observed histamine-induced relaxing effect was absent in preparations pre-contracted with KCl (120 mM) or in the presence of depolarizing nutritive solution. However, the histamine-induced relaxation was still present in the endothelium-removed preparations. The histamine-induced relaxation also was not prevented by astemizole (10(-6) M, 10(-5) M and 10(-4) M), cimetidine (10(-5) M, 10(-4) M and 10(-3) M) or thioperamide (10(-6) M, 10(-5) M and 10(-4) M), selective antagonists H(1), H(2) and H(3), respectively. The presence of L-NAME 10(-4) M or L-NAME 10(-4) M plus indomethacin 10(-5) M also did not prevent the histamine-induced relaxation observed in rat portal vein. Thus, the histamine-induced relaxation observed in rat portal vein appears to involve a non-endothelial hyperpolarizing mechanism independent of H(1), H(2) and H(3) receptors.
Rossignoli
Patrícia de S
Pde S
Laboratory of Pharmacology, Faculty of Medicine of Marília, São Paulo, Brazil.
Rodrigues
Andréa D
AD
Tinti
Thaís
T
Pereira
Oduvaldo C M
OC
Ellinger
Fred
F
Chies
Agnaldo B
AB
D000818:Animals; D016589:Astemizole / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology*; D017442:Histamine Agonists / Q000494:pharmacology*; D039563:Histamine H1 Antagonists, Non-Sedating / Q000494:pharmacology; D008297:Male; D023421:Models, Animal; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011169:Portal Vein / Q000187:drug effects* / Q000502:physiology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011969:Receptors, Histamine H1 / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D004791:Enzyme Inhibitors; D017442:Histamine Agonists; D039563:Histamine H1 Antagonists, Non-Sedating; D011969:Receptors, Histamine H1; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D011189:Potassium Chloride; D016589:Astemizole; D006632:Histamine; D019331:NG-Nitroarginine Methyl Ester