Static muscle contraction reflexly increases adrenal sympathetic nerve activity in rats

J. Vissing, L. B. Wilson, J. H. Mitchell, R. G. Victor

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Abstract

Little is known about the mechanisms responsible for activation of sympathoadrenal function during exercise. We hypothesized that sympathoadrenal discharge is activated at the onset of exercise by a reflex arising in the contracting muscle. Adrenal sympathetic nerve activity (SNA) was recorded during 1 min stimulation of the tibial nerve at two times motor threshold, before and during neuromuscular blockade, in 12 α-chloralose-anesthetized rats. Static muscle contractions, induced by stimulation before neuromuscular blockade, were repeated during ganglionic blockade (n = 6) to specifically test reflex activation of preganglionic activity to the adrenal gland. During static contraction, adrenal SNA rapidly increased (P < 0.05) to a maximum of 89 ± 12% above basal and then declined, reaching basal levels after 30 s of muscle contraction. Tibial nerve stimulation during neuromuscular blockade had no effect on adrenal SNA. In most rats, adrenal SNA decreased with ganglionic blockade, indicating postganglionic as well as preganglionic innervation of the adrenal gland. During ganglionic blockade, static muscle contractions elicited a 140 ± 21% increase in adrenal preganglionic SNA. In conclusion, static muscle contraction reflexly increases SNA to the adrenal gland, providing a mechanism for sympathoadrenal activation at the onset of exercise.

Original languageEnglish (US)
Pages (from-to)R1307-R1312
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume261
Issue number5 30-5
StatePublished - Dec 1 1991

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Keywords

  • Exercise
  • Musculoadreno medullary reflex
  • Sympathoadrenal function

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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