Recurrent laryngeal nerve activity exhibits a 5-HT-mediated long-term facilitation and enhanced response to hypoxia following acute intermittent hypoxia in rat

Tara G. Bautista, Tao Xing, Angelina Y. Fong, Paul M. Pilowsky*

*Corresponding author for this work

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

A progressive and sustained increase in inspiratory-related motor output ("long-term facilitation") and an augmented ventilatory response to hypoxia occur following acute intermittent hypoxia (AIH). To date, acute plasticity in respiratory motor outputs active in the postinspiratory and expiratory phases has not been studied. The recurrent laryngeal nerve (RLN) innervates laryngeal abductor muscles that widen the glottic aperture during inspiration. Other efferent fibers in the RLN innervate adductor muscles that partially narrow the glottic aperture during postinspiration. The aim of this study was to investigate whether or not AIH elicits a serotonin-mediated long-term facilitation of laryngeal abductor muscles, and if recruitment of adductor muscle activity occurs following AIH. Urethane anesthetized, paralyzed, unilaterally vagotomized, and artificially ventilated adult male Sprague-Dawley rats were subjected to 10 exposures of hypoxia (10% O 2 in N 2, 45 s, separated by 5 min, n = 7). At 60 min post-AIH, phrenic nerve activity and inspiratory RLN activity were elevated (39 ± 11 and 23 ± 6% above baseline, respectively). These responses were abolished by pretreatment with the serotonin-receptor antagonist, methysergide (n = 4). No increase occurred in time control animals (n = 7). Animals that did not exhibit postinspiratory RLN activity at baseline did not show recruitment of this activity post-AIH (n = 6). A repeat hypoxia 60 min after AIH produced a significantly greater peak response in both phrenic and RLN activity, accompanied by a prolonged recovery time that was also prevented by pretreatment with methysergide. We conclude that AIH induces neural plasticity in laryngeal motoneurons, via serotonin-mediated mechanisms similar to that observed in phrenic motoneurons: the so-called "Q-pathway". We also provide evidence that the augmented responsiveness to repeat hypoxia following AIH also involves a serotonergic mechanism.

Original languageEnglish
Pages (from-to)1144-1156
Number of pages13
JournalJournal of Applied Physiology
Volume112
Issue number7
DOIs
Publication statusPublished - Apr 2012

Keywords

  • 5-hydroxytryptamine
  • Laryngeal motoneuron
  • Long-term facilitation
  • Methysergide
  • Postinspiratory
  • Serotonin

Fingerprint Dive into the research topics of 'Recurrent laryngeal nerve activity exhibits a 5-HT-mediated long-term facilitation and enhanced response to hypoxia following acute intermittent hypoxia in rat'. Together they form a unique fingerprint.

  • Cite this