REFLEX LARYNGOSPASM INDUCED BY STIMULATION OF DISTAL ESOPHAGEAL AFFERENTS

Distal esophageal sensory nerves were stimulated in 17 anesthetized do gs divided into three age groups to determine the laryngeal, cardiovas cular, and respiratory effects. Group I puppies were 5 to 8 weeks of a ge, group II puppies were 8 to 19 weeks of age, and group III animals were adult dogs. Marked laryngeal adductor activity and laryngospasm w ere observed in group II puppies, while no or minimal laryngeal adduct ion was seen in younger puppies and adult dogs. Mean arterial pressure and heart rate increased significantly in groups II and III (P<.005) but remained unchanged in group I animals (P>.4). This response is dis tinctly different from the laryngeal chemoreflex because central apnea , hypotension, and bradycardia were absent. The afferent limb of the r esponse is mediated by the vagus nerve as bilateral transthoracic trun cal vagotomy eliminated the reflex. The laryngeal response observed fo llowing stimulation of distal esophageal afferent fibers may be import ant in the mechanism of apparent life-threatening events (ALTEs) and t he sudden infant death syndrome (SIDS) associated with gastroesophagea l reflux disease.