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Hypercapnia-induced micro-arousals during sleep: glutamatergic mechanisms in the parabrachial nucleus

Chunxiao Zhang1, Shihan Xu1, Mengjuan Wang2

  • 1Department of Physiology, College of Basic Medical Sciences, Jilin University, Changchun, China.

Sleep Medicine
|April 14, 2026
PubMed
Abstract

Insights

Hypercapnia during sleep apnea triggers micro-arousals by activating the medial parabrachial nucleus (MPB). This involves enhanced neuronal excitability and synaptic function, suggesting new therapeutic targets for sleep breathing disorders.

Area of Science:

  • Neuroscience
  • Sleep Medicine
  • Respiratory Physiology

Background:

  • Sleep apnea is associated with hypercapnia (elevated CO2).
  • Micro-arousals disrupt sleep quality and are linked to hypercapnia.
  • The medial parabrachial nucleus (MPB) is implicated in arousal and cardiorespiratory control.

Purpose of the Study:

  • To investigate the neural mechanisms of hypercapnia-induced micro-arousals.
  • To examine neuronal activation and synaptic function in the MPB during hypercapnia.
  • To understand the role of the MPB in sleep apnea pathophysiology.

Main Methods:

  • Mice were subjected to hypercapnic challenges during NREM sleep.
  • Micro-arousals were identified using EEG and hippocampal LFP.
  • Neuronal activation in the MPB was assessed via Fos immunohistochemistry.
  • In vitro slice electrophysiology (whole-cell patch-clamp) evaluated MPB neuronal excitability and synaptic currents (sEPSCs) under hypercapnic conditions.

Main Results:

  • Hypercapnia induced micro-arousals characterized by EEG/LFP desynchronization.
  • Cortical power in delta and theta bands decreased; hippocampal gamma and ripple oscillations were suppressed.
  • EMG activity increased, indicating arousal.
  • Fos expression in MPB neurons was elevated by hypercapnia.
  • In vitro, hypercapnic ACSF increased MPB neuronal firing frequency and sEPSC frequency.
  • NMDA/AMPA receptor blockade abolished these hypercapnic effects in MPB slices.

Conclusions:

  • Hypercapnia significantly alters cortical-hippocampal spectral dynamics and activates the MPB.
  • MPB activation, mediated by glutamatergic transmission, plays a key role in hypercapnia-induced micro-arousals.
  • These findings highlight the MPB as a potential therapeutic target for sleep breathing disorders.
Keywords:
ElectroencephalographHypercapniaMicro-arousalParabrachial nucleusSpontaneous excitatory postsynaptic current

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