Upper airway function during sleep and wakefulness: experimental studies on normal and anesthetized cats

Area of Science:

• Neuroscience
• Respiratory Physiology

Background:

• The posterior cricoarytenoid (PCA) muscles are crucial laryngeal abductors for maintaining upper airway patency during respiration.
• Understanding the neural control of PCA activity during different behavioral states (wakefulness, sleep) and its modulation by brainstem pathways is essential for respiratory health.

Purpose of the Study:

• To investigate the activity patterns of PCA muscles during wakefulness and sleep in cats.
• To identify brainstem sites influencing PCA and diaphragmatic activity.
• To elucidate the mechanisms of PCA modulation by brainstem stimulation.

Main Methods:

• Recording PCA muscle activity in normal and anesthetized cats during wakefulness and sleep stages.
• Mapping brainstem sites using electrical stimulation to observe effects on PCA and diaphragmatic activity.
• Analyzing changes in PCA motor unit discharge, burst duration, and recruitment patterns.

Main Results:

• PCA activity, prominent during inspiration in wakefulness, significantly declined during sleep, most notably in REM sleep.
• Barbiturate anesthesia mimicked either wakefulness or sleep PCA patterns depending on dosage.
• Brainstem stimulation revealed distinct facilitatory (rostral) and blocking (caudal) effects on PCA activity, influencing motor unit recruitment and burst characteristics.
• Facilitatory sites modulated PCA activity at lower stimulation intensities than diaphragmatic activity.
• Brainstem stimulation could induce phase switching of respiratory activity.

Conclusions:

• Sleep profoundly suppresses laryngeal abductor activity, potentially contributing to obstructive sleep apnea.
• Specific brainstem pathways exert significant control over PCA activity, offering insights into the neural regulation of breathing.
• The findings have implications for understanding and potentially treating sleep-related breathing disorders.