Skeletal muscle afferent fibres release substance P in the nucleus tractus solitarii of anaesthetized cats

Jeffrey T. Potts, Ingbert E. Fuchs, Jianhua Li, Bradley Leshnower, Jere H. Mitchell

Research output: Contribution to journalArticle

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Abstract

1. The tachykinin substance P was recovered from the commissural subdivision of the nucleus tractus solitarii (cNTS) using in vivo microdialysis during activation of cardiorespiratory and skeletal muscle receptors in thirteen chloralose-anaesthetized cats. 2. Tetanic muscle contraction was evoked by stimulating L7-S1 ventral roots (n = 7). Electrically induced muscle contraction increased mean arterial pressure (MAP) by 55 ± 10 mmHg and heart rate by 29 ± 6 beats min-1. During contraction the dialysate concentration increased 154% above resting control levels (from 0.217 ± 0.009 to 0.546 ± 0.023 fmol (100 μl)-1, control vs. contraction, P < 0.05). 3. Loss of cardiorespiratory input following disruption of the carotid sinus and vagus nerves significantly blunted, but did not abolish, the increase in substance P during muscle contraction (from 0.247 ± 0.022 to 0.351 ± 0.021 fmol (100 μl)-1, control vs. contraction, P < 0.05). Approximately 44% of the substance P release during contraction was independent of cardiorespiratory input transmitted by carotid sinus and vagus nerves. To determine the contribution of cardiorespiratory related neural input on substance P release, an intravascular balloon positioned in the thoracic aorta was inflated to increase arterial pressure (n = 6). Balloon inflation increased MAP by 50 ± 5 mmHg and substance P increased from 0.251 ± 0.025 to 0.343 ± 0.028 fmol (100 μl)-1 (control vs. balloon inflation, P < 0.05). This increase was completely abolished following interruption of vagal and carotid sinus nerves (from 0.301 ± 0.012 to 0.311 ± 0.014 fmol (100 μl)-1, control vs. balloon inflation). This finding shows that neural input from cardiorespiratory receptors (primarily arterial baroreceptors) accounted for 37% of the total substance P release during muscle contraction. 5. The findings from this study demonstrate that activation of skeletal muscle receptors and cardiorespiratory receptors (predominantly arterial baroreceptors) increases the extraneuronal concentration of substance P in the cNTB. Because substance P release was not completely abolished during muscle contraction following disruption of carotid sinus and vagus nerves it is proposed that: (1) afferent projections from contraction-sensitive skeletal muscle receptors may release substance P in the NTS; (2) neural input from muscle receptors activates substance P-containing neurones within the NTS; and (3) convergence of afferent input from skeletal muscle receptors and arterial baroreceptors onto substance P-containing neurones in the cNTS facilitates the release of substance P. The role of tachykininergic modulation of cardiorespiratory input is discussed.

Original languageEnglish (US)
Pages (from-to)829-841
Number of pages13
JournalJournal of Physiology
Volume514
Issue number3
DOIs
StatePublished - Feb 1 1999

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Solitary Nucleus
Skeletal Muscle Fibers
Substance P
Cats
Muscle Contraction
Carotid Sinus
Pressoreceptors
Vagus Nerve
Economic Inflation
Skeletal Muscle
Arterial Pressure
Neurokinin-1 Receptors
Neurons
Tachykinins
Chloralose
Spinal Nerve Roots
Dialysis Solutions
Microdialysis
Thoracic Aorta
Heart Rate

ASJC Scopus subject areas

  • Physiology

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Skeletal muscle afferent fibres release substance P in the nucleus tractus solitarii of anaesthetized cats. / Potts, Jeffrey T.; Fuchs, Ingbert E.; Li, Jianhua; Leshnower, Bradley; Mitchell, Jere H.

In: Journal of Physiology, Vol. 514, No. 3, 01.02.1999, p. 829-841.

Research output: Contribution to journalArticle

Potts, Jeffrey T. ; Fuchs, Ingbert E. ; Li, Jianhua ; Leshnower, Bradley ; Mitchell, Jere H. / Skeletal muscle afferent fibres release substance P in the nucleus tractus solitarii of anaesthetized cats. In: Journal of Physiology. 1999 ; Vol. 514, No. 3. pp. 829-841.
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