Effects of static muscular contraction on impulse activity of groups III and IV afferents in cats

M. P. Kaufman, J. C. Longhurst, K. J. Rybicki, J. H. Wallach, J. H. Mitchell

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Abstract

Static contraction of the hindlimb muscles, induced by electrical stimulation of the ventral roots, reflexly increases arterial blood pressure and heart rate. Although stimulation of groups III and IV muscle afferents is believed to cause these reflex increases, the responses of these afferents to a level of static contraction that increases arterial pressure have not yet been determined. Therefore, in barbiturate-anesthetized cats, afferent impulses arising from endings in the gastrocnemius muscle were recorded from the L7 or S1 dorsal roots, while the cut peripheral end of the L7 ventral root was stimulated. In addition, the effects of capsaicin (100-200 μg) and bradykinin (25 μg) on the activity of the groups III and IV afferents stimulated by contraction were examined. Contraction of the gastrocnemius muscle to a level equal to or greater than that needed to cause a pressor response stimulated 12 of 19 (63%) group III afferents and 13 of 19 (68%) group IV afferents. However, the discharge patterns of the group III afferents stimulated by contraction were very different from those of the group IV fibers. No relationship was found between those fibers stimulated by contraction and those stimulated by chemicals. Our results suggest that although both groups III and IV muscle afferents contribute to the reflex cardiovascular increases evoked by static exercise, group III fibers were likely to be stimulated by the mechanical effects of muscular contraction, whereas at least some group IV fibers were likely to be stimulated by the metabolic products of muscular contraction.

Original languageEnglish (US)
Pages (from-to)105-112
Number of pages8
JournalJournal of Applied Physiology Respiratory Environmental and Exercise Physiology
Volume55
Issue number1 I
StatePublished - 1983

Fingerprint

Spinal Nerve Roots
Muscle Contraction
Cats
Reflex
Arterial Pressure
Skeletal Muscle
Muscles
Capsaicin
Bradykinin
Hindlimb
Electric Stimulation
Heart Rate

ASJC Scopus subject areas

  • Physiology
  • Endocrinology

Cite this

Effects of static muscular contraction on impulse activity of groups III and IV afferents in cats. / Kaufman, M. P.; Longhurst, J. C.; Rybicki, K. J.; Wallach, J. H.; Mitchell, J. H.

In: Journal of Applied Physiology Respiratory Environmental and Exercise Physiology, Vol. 55, No. 1 I, 1983, p. 105-112.

Research output: Contribution to journalArticle

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