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      Vasopressin inhibits sympathetic ganglionic transmission but potentiates sympathetic neuroeffector responses in hindlimb vasculature of rabbits.

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      The Journal of pharmacology and experimental therapeutics

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          Abstract

          To determine whether vasopressin (AVP) affects vasoconstrictor responses to electrical stimulation of sympathetic nerves or i.a. norepinephrine (NE), changes in perfusion pressure were measured during lumbar sympathetic nerve stimulation (LSNS, 1-8 Hz), or administration of NE (50-200 ng), in the isolated constant-flow perfused hind limb of chloralose-anesthetized rabbits (n = 7), before and after i.a. infusion of AVP (0.65 mU/kg/min). AVP significantly potentiated responses to LSNS (relative potency (RP) = 1.59) and to NE (RP = 5.17). The potentiation of LSNS and NE by AVP infusion was abolished by the AVP V1 antagonist, d(CH2)5[Tyr(Me)2]AVP, 400 ng, total dose (n = 6). Because there was a significant difference between the RP of LSNS (stimulation of both preganglionic and postganglionic nerves) and NE (direct effect on the vascular smooth muscle), we verified whether this difference might represent disparate actions of AVP on the ganglia and/or sympathetic neuroeffector sites. To evaluate responses to stimulating only the postganglionic sympathetic nerves, we repeated the above study in animals pretreated with a supramaximal dose of the ganglionic blocking agent hexamethonium (25 mg/kg i.v.). After ganglionic blockade the responses to LSNS were reduced to 22% of control. In the presence of ganglionic blockade, AVP potentiated responses to LSNS (RP = 4.09) (n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

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          Author and article information

          Journal
          J. Pharmacol. Exp. Ther.
          The Journal of pharmacology and experimental therapeutics
          0022-3565
          0022-3565
          Jun 1988
          : 245
          : 3
          Affiliations
          [1 ] Department of Physiology and Pharmacology, University of South Dakota, Vermillion.
          Article
          2898522
          d286d12d-5973-4ee8-abc5-315b4bd8ed8e
          History

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