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Title: After-Discharge in the Upper Airway Muscle Genioglossus Following Brief Hypoxia.
Austin Authors: Avraam, Joanne ;Dawson, Andrew;Feast, Nicole;Fan, Feiven Lee;D Frigant, Monika;Kay, Amanda;Koay, Zi Yi;Jia, Pingdong;Greig, Rachel;Thornton, Therese;Nicholas, Christian L;O'Donoghue, Fergal J ;Trinder, John;Jordan, Amy S 
Affiliation: Respiratory and Sleep Medicine
Faculty of Medicine, University of Melbourne, Parkville, Victoria, Australia
Melbourne School of Psychological Sciences, University of Melbourne, Melbourne, Australia
Institute for Breathing and Sleep
Issue Date: 2-Apr-2021 2021-04-02
Publication information: Sleep 2021; online first: 2 April
Abstract: Genioglossus after-discharge is thought to protect against pharyngeal collapse by minimising periods of low upper airway muscle activity. How genioglossus after-discharge occurs and which single motor units (SMUs) are responsible for the phenomenon are unknown. The aim of this study was to investigate genioglossal after-discharge. During wakefulness, after-discharge was elicited 8-12 times in healthy individuals with brief isocapnic hypoxia (45-60s of 10%O2 in N2) terminated by a single breath of 100% O2. Genioglossus SMUs were designated as firing solely, or at increased rate, during inspiration (Inspiratory phasic [IP] and inspiratory tonic [IT] respectively); solely, or at increased rate, during expiration (Expiratory phasic [EP] or expiratory tonic [ET] respectively) or firing constantly without respiratory modulation (Tonic). SMUs were quantified at baseline, the end of hypoxia, the hyperoxic breath and the following 8 normoxic breaths. 210 SMU's were identified in 17 participants. Genioglossus muscle activity was elevated above baseline for 7 breaths after hyperoxia (p<0.001), indicating a strong after-discharge effect. After-discharge occurred due to persistent firing of IP and IT units that were recruited during hypoxia, with minimal changes in ET, EP or Tonic SMUs. The firing frequency of units that were already active changed minimally during hypoxia or the afterdischarge period (P>0.05). That genioglossal after-discharge is almost entirely due to persistent firing of previously silent inspiratory SMUs provides insight into the mechanisms responsible for the phenomenon and supports the hypothesis that the inspiratory and expiratory/tonic motor units within the muscle have idiosyncratic functions.
DOI: 10.1093/sleep/zsab084
PubMed URL: 33822200
Type: Journal Article
Subjects: Upper airway dilator muscles
obstructive sleep apnea
pharyngeal collapse
short-term potentiation
Appears in Collections:Journal articles

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