Antihistamine-sensitive active vasodilatation in the perfused hindquarters of the rat.
The innervated, constant flow perfused hindquarters of the rat have been used to evaluate post-stimulation vasodilatation, which is a model of active reflex vasodilatation in this species. The vasodilatation resulting from lumbar sympathetic stimulation was dependent on stimulation frequency and duration. Maximal vasodilatation (16 +/- 2%) was at 8 Hz for 15 s, while markedly reduced vasodilatation was seen after stimulation for longer than 30 s at all frequencies tested. The vasodilatation was transient. Atropine (2.0 mg kg-1 i.v.) failed to attenuate post-stimulation vasodilatation at a time when hindquarter vasodilatation to i.a. acetylcholine had been abolished. The H1 antihistamine, tripelennamine (2.5 mg kg-1 i.v.) significantly reduced (77%) post-stimulation vasodilatation relative to controls at a time when hindquarter vasodilatation due to i.a. histamine was essentially abolished. Reactive hyperaemia is an unlikely cause of vasodilatation since it is not blocked by H1 antihistamines; 60 s post-occlusion hyperaemia also, was not demonstrable. These data suggest that there is an active component of baroreceptor-mediated vasodilatation in the rat and that histamine, rather than acetylcholine, could be a mediator of this vasodilatation.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004558:Electric Stimulation; D006614:Hindlimb / Q000098:blood supply / Q000294:innervation; D006632:Histamine / Q000502:physiology*; D008297:Male; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000502:physiology; D014309:Tripelennamine / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects
D014309:Tripelennamine; D001285:Atropine; D006632:Histamine