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

Abstract

SUMMARY1. Action potentials were recorded from single afferent units of the superior laryngeal nerves in neonatal and adult sheep, cats and monkeys when liquids were passed over the laryngeal mucosa. 2. Two types of mucosal receptors, sensitive to water but not to isotonic saline, were found in each species from birth. The most common type of unit responded after a short latency ( < 1 sec), discharged maximally in the first 1-3 see and became inactive when the stimulus was withdrawn. The other type responded only after several seconds, the discharges gradually increasing in frequency and continuing after removal of the stimulus.3. Reproducible responses were elicited by tactile stimulation of the laryngeal mucosa over the receptive field of each of the long-latency units. Fewer than 50 % of the short-latency units were excited, the remainder responding only unreproducibly to firm pressure.4. Short-latency, but not long-latency, units responded to milks, gastric contents, saliva and isotonic solutions of sugars.5. The responses of long-latency units to water were often modified by, but rarely dependent on, reflexly evoked activity in laryngeal muscles.6. The conduction velocities of afferent fibres of water sensitive units ranged from 22 to 49 m/sec, and differed little from those of water-insensitive laryngeal mechanoreceptors.7. Histological examination of the laryngeal mucosa showed that taste buds were present in lambs from birth whereas they developed post-natally in kittens and monkeys. The evidence suggests that taste buds were not associated with watersensitive units.

Effects of Age, Gender, Bolus Volume, and Trial on Swallowing Apnea Duration and Swallow/Respiratory Phase Relationships of Normal Adults

“…Moreover, an apneic reflex is believed to exist in humans as demonstrated by stimulating the pharyngeal region with water in sheep inducing apnea with a subsequent swallow [3]. However, this apneic reflex demonstrated in sheep can only be generalized to humans with caution as the apneic reflex was found in a nonhuman species and varying reflex mechanisms may exist.…”

Maturation of cough and other reflexes that protect the fetal and neonatal airway

“…Saline introduced into the larynx in the same manner had little or no affect. Others went on to confirm these findings in the neonatal lamb, dog, pig, cat and monkey [11][12][13][14][15][16]. Cough was not described due to the fact that the animals were tracheostomized.…”

Investigating the Complexity of Respiratory Patterns during the Laryngeal Chemoreflex

“…The laryngeal chemoreflex (LCR) has been investigated in many epidemiological and physiological studies as a putative exogenous stressor that may contribute to the pathogenesis of sudden infant death syndrome (SIDS) [1][2][3]. The triple-risk model proposed for SIDS states that death occurs at the confluence of three factors -a inherently vulnerable infant, exposed to an exogenous stressor during a critical period of postnatal development [4].…”