Liquid-sensitive laryngeal receptors in the developing sheep, cat and monkey

Area of Science:

• Neuroscience
• Physiology
• Comparative Anatomy

Background:

• The superior laryngeal nerve innervates the larynx, playing a role in swallowing and airway protection.
• Understanding laryngeal sensory mechanisms is crucial for deciphering reflexes involved in feeding and respiration.

Purpose of the Study:

• To investigate the characteristics of laryngeal mucosal receptors sensitive to water in different mammalian species.
• To differentiate water-sensitive receptors from other mechanoreceptors and taste receptors in the larynx.

Main Methods:

• Recording action potentials from single afferent units of the superior laryngeal nerves in neonatal and adult sheep, cats, and monkeys.
• Stimulating the laryngeal mucosa with various liquids (water, saline, milk, etc.) and tactile stimuli.
• Histological examination of laryngeal mucosa to identify taste bud development.

Main Results:

• Two distinct types of water-sensitive mucosal receptors were identified: short-latency and long-latency units.
• Short-latency units responded rapidly to water and other liquids, while long-latency units showed a delayed, sustained response primarily to water.
• Water-sensitive units were not associated with taste buds, which showed species-specific developmental patterns.

Conclusions:

• The larynx possesses specialized water-sensitive receptors distinct from taste receptors.
• These receptors exhibit differential responses to various liquids, suggesting unique physiological roles.
• The findings provide insights into the neural control of laryngeal reflexes related to fluid intake.