Keith F. Clark, MS, MD, Jay P. Farber, PhD

The goal of this study was to determine whether sensory fibers in an intact recurrent laryngeal nerve (RLN) are influenced by respiration or vocalization. Patterns of RLN afferent activity were examined during respiration and evoked vocalization by means of midbrain electrical stimulation in cats anesthetized with a-chloralose. Nerve bundles were dissected from an intact RLN, with motor function preserved. The bundles were cut and the laryngeal end was placed on floating bipolar electrodes. Fifteen right RLNs were examined. A total of 9 single and multiunit afferent fibers from 4 cats were isolated and examined during respiration. Four units, analyzed from 3 fibers, showed respiratory phase modulation. Eight units, analyzed from 4 fibers in I cat, were observed during vocalization and showed no vocalization phase modulation. The RLN afferents could contribute to reflex modulation of the respiratory cycle, but more extensive sampling would be necessary to preclude effects from vocalization.