Neural drive to tongue protrudor and retractor muscles following pulmonary C-fiber activation

Kun Ze Lee, David D. Fuller, I. Jung Lu, Jin Tun Lin, Ji Chuu Hwang

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Hypoglossal (XII) nerve recordings indicate that pulmonary C-fiber (PCF) receptor activation reduces inspiratory bursting and triggers tonic discharge. We tested three hypotheses related to this observation: 1) PCF receptor activation inhibits inspiratory activity in XII branches innervating both tongue protrudor muscles (medial branch; XIIMED) and retractor muscles (lateral branch; XIILAT); 2) reduced XII neurogram amplitude reflects decreased XII motoneuron discharge rate; and 3) tonic XII activity reflects recruitment of previously silent motoneurons. Phrenic, XIIMED, and XIILAT neurograms were recorded in anesthetized, paralyzed, and ventilated rats. Capsaicin delivered to the jugular vein reduced phrenic bursting at doses of 0.625 and 1.25 μg/kg but augmented bursting at 5 μg/kg. All doses reduced inspiratory amplitude in XIIMED and XIILAT (P < 0.05), and these effects were eliminated following bilateral vagotomy. Single-fiber recordings indicated that capsaicin causes individual XII motoneurons to either decrease discharge rate (n = 101/153) or become silent (n = 39/153). Capsaicin also altered temporal characteristics such that both XIIMED and XIILAT inspiratory burst onset occurred after the phrenic burst (P < 0.05). Increases in tonic discharge after capsaicin were greater in XIIMED vs. XIILAT (P < 0.05); single-fiber recordings indicated that tonic discharge reflected recruitment of previously silent motoneurons. We conclude that PCF receptor activation reduces inspiratory XII motoneuron discharge and transiently attenuates neural drive to both tongue protrudor and retractor muscles. However, tonic discharge appears to be selectively enhanced in tongue protrudor muscles. Accordingly, reductions in upper airway stiffness associated with reduced XII burst amplitude may be offset by enhanced tonic activity in tongue protrudor muscles.

Original languageEnglish
Pages (from-to)434-444
Number of pages11
JournalJournal of Applied Physiology
Volume102
Issue number1
DOIs
Publication statusPublished - 2007 Jan 1

Fingerprint

Unmyelinated Nerve Fibers
Motor Neurons
Tongue
Capsaicin
Muscles
Lung
Diaphragm
Personnel Selection
Hypoglossal Nerve
Vagotomy
Jugular Veins

Keywords

  • Hypoglossal motoneurons
  • Rat

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Neural drive to tongue protrudor and retractor muscles following pulmonary C-fiber activation. / Lee, Kun Ze; Fuller, David D.; Lu, I. Jung; Lin, Jin Tun; Hwang, Ji Chuu.

In: Journal of Applied Physiology, Vol. 102, No. 1, 01.01.2007, p. 434-444.

Research output: Contribution to journalArticle

Lee, Kun Ze ; Fuller, David D. ; Lu, I. Jung ; Lin, Jin Tun ; Hwang, Ji Chuu. / Neural drive to tongue protrudor and retractor muscles following pulmonary C-fiber activation. In: Journal of Applied Physiology. 2007 ; Vol. 102, No. 1. pp. 434-444.
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