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      Factors Influencing the Release of Purines and Norepinephrine in the Rabbit Portal Vein


      Journal of Vascular Research

      S. Karger AG

      Co-release, Purines, Norepinephrine, Prazosin, Yohimbine, Clonidine, 6-Hydroxydopamine

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          Previous studies have shown that transmural electrical stimulation (TES) of the rabbit portal vein in vitro, results in the overflow of <sup>3</sup>H-purines from tissues prelabelled with <sup>3</sup>H-adenosine. The purpose of the present study was to assess the possible sites which contribute to the TES-induced overflow of purines in this adrenergically innervated tissue. The contribution of postjunctional elements to purine overflow was assessed with the α<sub>1</sub>-adrenoceptor antagonist, prazosin. Prazosin (3 × 10<sup>–7</sup> M) did not affect the release of <sup>3</sup>H-norepinephrine but markedly reduced the TES-induced contraction. The release of <sup>3</sup>H-purines was reduced by 20% by prazosin, indicating that approximately 80% of the release is independent of the α<sub>1</sub>-mediated postjunctional response and, therefore, probably originates from neuronal sites in the tissue. Two lines of evidence indicate that a considerable portion of the α<sub>1</sub> -adrenoceptor-independent release of <sup>3</sup>H-purines (i.e., in the presence of prazosin) arises from adrenergic nerves. First, the fractional release of <sup>3</sup>H-purines was enhanced and reduced, respectively, by the α<sub>2</sub>-adrenoceptor antagonist, yohimbine, and the α<sub>2</sub>-adrenoceptor agonist, clonidine, in concentrations (10<sup>–6</sup> M) which did likewise to the fractional release of <sup>3</sup>H-norepinephrine. Second, destruction of the adrenergic nerves by in vitro treatment with 6-hydroxydopamine reduced the fractional release of <sup>3</sup>H-purines by 55 %. The release of purines which remains after 6-hydroxydopamine treatment may occur from non-adrenergic nerves.

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          Author and article information

          J Vasc Res
          Journal of Vascular Research
          S. Karger AG
          19 September 2008
          : 19
          : 1
          : 30-40
          Department of Pharmacology and Toxicology, West Virginia University Medical Center, Morgan town, W.Va., USA
          158371 Blood Vessels 1982;19:30–40
          © 1982 S. Karger AG, Basel

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          Page count
          Pages: 11
          Research Paper


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