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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Chronic intermittent hypoxia increases excitability and synaptic excitation of protrudor and retractor hypoglossal motoneurones

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Author(s):
da Silva, Melina P. [1] ; Magalhaes, Karolyne S. [1] ; de Souza, Daniel P. [1] ; Moraes, Davi J. A. [1]
Total Authors: 4
Affiliation:
[1] Univ Sao Paulo, Sch Med Ribeirao Preto, Dept Physiol, BR-14049900 Ribeirao Preto, SP - Brazil
Total Affiliations: 1
Document type: Journal article
Source: JOURNAL OF PHYSIOLOGY-LONDON; v. 599, n. 6 FEB 2021.
Web of Science Citations: 0
Abstract

Key points Dysfunctions in the hypoglossal control of tongue extrinsic muscles are implicated in obstructive sleep apnoea (OSA) syndrome. Chronic intermittent hypoxia (CIH), an important feature of OSA syndrome, produces deleterious effects on the motor control of oropharyngeal resistance, but whether the hypoglossal motoneurones innervating the tongue extrinsic muscles are affected by CIH is unknown. We show that CIH enhanced the respiratory-related activity of rat hypoglossal nerve innervating the protrudor and retractor tongue extrinsic muscles. Intracellular recordings revealed increases in respiratory-related firing frequency and synaptic excitation of inspiratory protrudor and retractor hypoglossal motoneurones after CIH. CIH also increased their intrinsic excitability, depolarised resting membrane potential and reduced K+-dominated leak conductance. CIH affected the breathing-related synaptic control and intrinsic electrophysiological properties of protrudor and retractor hypoglossal motoneurones to optimise the neural control of oropharyngeal function. Inspiratory-related tongue movements and oropharyngeal motor actions are controlled mainly by the protrudor and retractor extrinsic tongue muscles, which are innervated by the hypoglossal motoneurones. Chronic intermittent hypoxia (CIH), an important feature of obstructive sleep apnoea syndrome, produces detrimental effects on the contractile function of the tongue extrinsic muscles and the medullary inspiratory network of rodents. However, the impact of the CIH on the electrophysiological properties of protrudor and retractor hypoglossal motoneurones has not been described before. Using nerves and intracellular recordings in in situ preparation of rats (5 weeks old), we tested the hypothesis that CIH (FiO(2) of 0.06, SaO(2) 74%, during 30-40 s, every 9 min, 8 h/day for 10 days) increases the intrinsic excitability of protrudor and retractor motoneurones from the hypoglossal motor nucleus of rats. Recordings of hypoglossal nerve, before its bifurcation to innervate the tongue protrudor and retractor muscles, revealed that CIH enhances its pre-inspiratory, simultaneously with the presence of active expiration, and inspiratory activities. These changes were mediated by increases in the respiratory-related firing frequency and synaptic excitation of inspiratory protrudor and retractor hypoglossal motoneurones. Besides, CIH increases their intrinsic excitability and depolarises resting membrane potential by reducing a K+-dominated leak conductance. In conclusion, CIH enhances the respiratory-related neural control of oropharyngeal function of rats by increasing the synaptic excitation, intrinsic excitability, and reducing leak conductance in both protrudor and retractor hypoglossal motoneurones. We propose that these network and cellular changes are important to optimise the oropharyngeal resistance in conditions related to intermittent hypoxia. (AU)

FAPESP's process: 18/15957-2 - Astrocytic modulation on brainstem neurons involved with generation and control of sympathetic and respiratory activities in rodents submitted to hypoxia
Grantee:Benedito Honorio Machado
Support Opportunities: Research Projects - Thematic Grants
FAPESP's process: 19/11863-6 - Synaptic transmission and electrophysiological properties of bronchial motoneurons of the dorsal motor nucleus of the vagus from rats
Grantee:Davi José de Almeida Moraes
Support Opportunities: Regular Research Grants
FAPESP's process: 19/24060-9 - Contribution of the parafacial Respiratory Group to the inspiratory, expiratory and cardiovascular responses of rats to muscle afferent fiber stimulation
Grantee:Karolyne Silva Magalhães
Support Opportunities: Scholarships in Brazil - Doctorate
FAPESP's process: 18/07027-5 - Role of astrocytes in the excitability of magnocelular neurons form supraoptic nucleus during changes in the plasma osmolality
Grantee:Melina Pires da Silva
Support Opportunities: Research Grants - Young Investigators Grants