Active expiratory oscillator regulates nasofacial and oral motor activities in rats

Author(s)

de Britto, Alan A. ^[1] ; Magalhaes, Karolyne S. ^[1] ; da Silva, Melina P. ^[1] ; Paton, Julian F. R. ^[2] ; Moraes, Davi J. A. ^[1]

Affiliation

^[1] Univ Sao Paulo, Sch Med Ribeirao Preto, Dept Physiol, BR-14049900 Ribeirao Preto, SP - Brazil

^[2] Univ Auckland, Dept Physiol, Fac Med & Hlth Sci, Pk Rd, Auckland - New Zealand

• Document type: Journal article
• Source: Experimental Physiology; v. 105, n. 2 JAN 2020.
• Web of Science Citations: 0

Abstract

New Findings What is the central question of this study?Does the parafacial respiratory group (pFRG), which mediates active expiration, recruit nasofacial and oral motoneurons to coordinate motor activities that engage muscles controlling airways in rats during active expiration. What is the main finding and its importance?Hypercapnia/acidosis or pFRG activation evoked active expiration and stimulated the motoneurons and nerves responsible for the control of nasofacial and oral airways patency simultaneously. Bilateral pFRG inhibition abolished active expiration and the simultaneous nasofacial and oral motor activities induced by hypercapnia/acidosis. The pFRG is more than a rhythmic oscillator for expiratory pump muscles: it also coordinates nasofacial and oral motor commands that engage muscles controlling airways. Active expiration is mediated by an expiratory oscillator located in the parafacial respiratory group (pFRG). Active expiration requires more than contracting expiratory muscles as multiple cranial nerves are recruited to stabilize the naso- and oropharyngeal airways. We tested the hypothesis that activation of the pFRG recruits facial and trigeminal motoneurons to coordinate nasofacial and oral motor activities that engage muscles controlling airways in rats during active expiration. Using a combination of electrophysiological and pharmacological approaches, we identified brainstem circuits that phase-lock active expiration, nasofacial and oral motor outputs in an in situ preparation of rat. We found that either high chemical drive (hypercapnia/acidosis) or unilateral excitation (glutamate microinjection) of the pFRG evoked active expiration and stimulated motoneurons (facial and trigeminal) and motor nerves responsible for the control of nasofacial (buccal and zygomatic branches of the facial nerve) and oral (mylohyoid nerve) motor outputs simultaneously. Bilateral pharmacological inhibition (GABAergic and glycinergic receptor activation) of the pFRG abolished active expiration and the simultaneous nasofacial and oral motor activities induced by hypercapnia/acidosis. We conclude that the pFRG provides the excitatory drive to phase-lock rhythmic nasofacial and oral motor circuits during active expiration in rats. Therefore, the pFRG is more than a rhythmic oscillator for expiratory pump muscles: it also coordinates nasofacial and oral motor commands that engage muscles controlling airways in rats during active expiration. (AU)

• FAPESP's process: 15/01073-7 - Electrophysiological characterization of expiratory motoneurons in rats submitted to sustained hypoxia
• Grantee: Melina Pires da Silva
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/10484-5 - Electrophysiological and molecular characterization of neurons involved in the generation of respiratory rhythm and pattern of rats during postnatal development
• Grantee: Davi José de Almeida Moraes
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 17/09071-9 - Participation of the noradrenergic neurons of locus coeruleus in the central generation of inspiratory and expiratory activities in response to the activation of the central chemoreceptors of rats
• Grantee: Karolyne Silva Magalhães
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 16/24994-3 - Participation of parafacial respiratory group in the orofacial and nasofacial motor responses of rats induced by activation of peripheral and central chemoreceptors
• Grantee: Alan Andrade de Britto
• Support Opportunities: Scholarships in Brazil - Scientific Initiation