Sympathetic stimulation elicits increased or decreased V̇O2 in the perfused rat hindlimb via α1-adrenoceptors

Jennifer L. Hall, J. I Ming Ye, Michael G. Clark, Eric Q. Colquhoun

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11 Scopus citations

Abstract

The effects of lumbar sympathetic nerve stimulation on oxygen uptake (V̇O2) in curarized muscle of the perfused rat hindlimb were investigated. Stimulation of sympathetic nerves elicited vasoconstriction at all frequencies. Importantly, this was associated with changes in V̇O2 that were generally stimulatory at low frequencies (0.5-2 Hz) and inhibitory at high frequencies (5-10 Hz). Both the pressor response and the changes in V̇O2 were almost completely blocked by the α12-blocker phentolamine (1.0 μM) but were not affected by the β12-blocker DL-propranolol (2.0 μM). The α2-blocker yohimbine (0.1 μM) did not significantly affect either the pressor or V̇O2 response. The α1-antagonist prazosin (0.1 μM) abolished the vasoconstriction with low frequency stimulation and inhibited >90% of the vasoconstriction with high-frequency stimulation. Intra-arterial infusion of phenylephrine (α1-agonist), but not of UK-14304 (α2-agonist), also elicited a similar biphasic response in V̇O2 during vasoconstriction. The changes in V̇O2 at both low- and high-frequency stimulation were fully reversed by prazosin. The vasodilator sodium nitroprusside also showed similar effects to prazosin in blocking both. V̇O2 and vasoconstriction. Thus sympathetic control of V̇O2 in the perfused rat hindlimb appears to be initiated by activation of predominantly vascular α1-adrenoceptors.

Original languageEnglish (US)
Pages (from-to)H2146-H2153
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume272
Issue number5 41-5
DOIs
StatePublished - Jan 1 1997

Keywords

  • adrenergic agonists
  • adrenergic antagonists
  • nonnutritive flow
  • nutritive flow
  • oxygen uptake
  • vascular control
  • vasoconstriction

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