Characteristics of laryngeal cold receptors.

This study was designed to further characterize the properties of previously described laryngeal cold receptors (Respir. Physiol. 59:35, 1985). Single unit action potentials were recorded from the internal branch of the superior laryngeal nerve (SLN) in anesthetized, spontaneously breathing dogs. The nervous conduction of fibers originating from 12 laryngeal cold receptors was blocked at a mean (+/- SE) temperature of 18.8 +/- 0.7 degrees C. Twelve receptors were localized on the edge of the vocal folds in correspondence of the vocal process of the arytenoid cartilage. Topical anesthesia (2% lidocaine) blocked their activity within 4-18 sec, suggesting a superficial location. Paralysis of the vocal folds during spontaneous breathing through the upper airway did not alter the activity of 9 of 13 cold receptors. On the other hand, 7 of 12 cold receptors tested with constant flow showed respiratory modulation and laryngeal paralysis abolished the modulation of 3 of these tested with a constant flow of air. During progressive cooling in a stepwise fashion, as in frigid air breathing, laryngeal cold receptors maintained a phasic discharge. Our results indicate that these endings are particularly suited for detecting changes in temperature.