Neuronal mechanisms underlying the laryngeal adductor reflex

Area of Science:

• Neuroscience
• Respiratory Physiology
• Laryngeal Reflexes

Background:

• The laryngeal adductor reflex involves glottal closure upon laryngeal stimulation.
• This reflex presents as an early ipsilateral (R1) and a late bilateral (R2) response.
• Understanding the physiological basis of these responses is crucial.

Purpose of the Study:

• To investigate the physiological properties of R1 and R2 responses.
• To record responses from expiratory laryngeal motoneurons (ELMs) in rats during superior laryngeal nerve (SLN) stimulation.

Main Methods:

• Single unit extracellular recordings from 5 ELMs in 4 Sprague-Dawley rats.
• ELMs identified by antidromic responses to recurrent laryngeal nerve stimulation and postinspiratory firing.
• Unilateral SLN stimulation at 20 Hz.

Main Results:

• SLN stimulation inhibited phrenic nerve and ELM postinspiratory activity.
• ELMs exhibited tonic firing with short-latency (5-10 ms) action potentials (90% occurrence) from ipsilateral SLN stimulation.
• Long-latency (20-50 ms) action potentials occurred with bilateral SLN stimulation (47% ipsilateral, 58% contralateral).

Conclusions:

• The R1 response is attributed to short-latency action potentials from ipsilateral SLN stimulation.
• The R2 response is likely mediated by long-latency action potentials in ELMs on both sides.