Dynamic exercise attenuates sympathetic responsiveness of canine vascular smooth muscle

Stephen B. Ruble, Zoran Valic, John B. Buckwalter, Philip S. Clifford

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The phenomenon of reduced responsiveness of the skeletal muscle arterial vasculature to sympathetic activation during exercise (sympatholysis) remains controversial. The purpose of this study was to examine the vascular effects of sympathoactivation in dynamically exercising skeletal muscle. Mongrel dogs (19-24 kg) were instrumented chronically with transit-time ultrasonic flow probes on the external iliac arteries. After pre-treatment with atropine (0.2 mg/kg), an intravenous bolus (4 μg/kg) of a nicotinic ganglion stimulant [1,1-dimethyl-4-phenylpiperazinium iodide (DMPP)] was given at rest and during treadmill exercise at graded intensities. Administration of DMPP was associated with prompt reductions in iliac blood flow and increases in arterial pressure under all conditions. There were significant reductions (P < 0.05) in iliac vascular conductance of 58 ± 4 (SE), 48 ± 3, 36 ± 5, and 16 ± 3% at rest, 3 miles/h and 0% grade, 6 miles/h and 0% grade, and 6 miles/h and 15% grade, respectively. These data demonstrate that activation of postganglionic sympathetic nerves with DMPP caused vasoconstriction in the skeletal muscle vasculature at rest and during exercise. Additionally, the magnitude of vasoconstriction was inversely related to exercise intensity. These results support the concept of exercise sympatholysis.

Original languageEnglish
Pages (from-to)2294-2299
Number of pages6
JournalJournal of Applied Physiology
Volume89
Issue number6
DOIs
StatePublished - 2000
Externally publishedYes

Keywords

  • Adrenergic
  • Blood flow
  • Sympathetic nervous system
  • Sympatholysis
  • Vascular conductance

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