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      Differences in the Response of Three Embryologically Distinct Segments of the Isolated Canine Posterior Vena cava to Vasoactive Substances

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          The canine posterior vena cava was excised and divided into three embryologically distinct segments: segment A (supradiaphragm), segment B-C (intra-hepatic and that between liver and renal veins), and segment D (infrarenal). Circular and longitudinal strips were cut from each segment, suspended in Krebs bicarbonate solution and isometric tensions were recorded. The responses to six vasoactive agents, as well as transmural neural stimulation were studied. Maximum tension and ED<sub>50</sub> were obtained for norepinephrine, epinephrine, acetylcholine, bradykinin, histamine and 5-hydroxytryptamine (5-HT). The responses were not only quantitatively, but qualitatively different among the three segments. Bradykinin constricted the strip:; in A and B-C but not in D. 5-HT (<10<sup>–5</sup> m) caused a dose-dependent contraction in A and D through its direct stimulating action, while in C, a contractile response appeared only after administration of a higher dose of 5-HT. This was due to an indirect sympathomimetic action of the agent. Segment B-C, which histologically contained massive longitudinal muscle bundles in the outer layer of the wall, exhibited spontaneous, rhythmic contractions. The existence of a cholinergic excitatory innervation, in addition to adrenergic, was demonstrated in C by transmural neural stimulation.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          18 September 2008
          : 15
          : 1-3
          : 157-169
          Department of Pharmacology, Nagoya University School of Medicine, Showa-Xu, Nagoya
          158161 Blood Vessels 1978;15:157–169
          © 1978 S. Karger AG, Basel

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          Page count
          Pages: 13
          Molecular and Cellular Aspects of Vascular Smooth Muscle in Health and Disease


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