Abstract
Expulsive phase of cough is produced by a large contraction of abdominal muscles. To understand neuronal mechanisms controlling this phase, the activity of augmenting expiratory (aug-E) neurons were investigated during fictive cough in decerebrate and paralyzed cats. Repetitive stimulation of the superior laryngeal nerve produced fictive cough characterized by an increased augmenting discharge in the phrenic nerve (stage 1 of cough; SC1) and large decrementing discharge in the iliohypogastric nerve (stage 2 of cough; SC2). Aug-E neurons showed 3 types of responses during fictive cough. A half (14/28) of aug-E neurons gradually depolarized during the SC1 phase and abruptly depolarized with high frequency discharges during the SC2 phase (D-D type). Ten other neurons showed no detectable change during the SC1 phase and a large decrementing depolarization during the SC2 phase (N-D type). The remaining 4 neurons hyperpolarized during the SC1 and SC2 phases (H-H type). In contrast, postinspiratory (post-I) and augmenting inspiratory (aug-I) neurons showed uniform responses during fictive cough. Post-I neurons (n=13) depolarized during both SC1 and SC2 phases. Aug-I (n=6) showed an increased depolarization during the SC1 phase and large hyperpolarization during the SC2 phase. The present results demonstrated heterogeneity of aug-E neurons in their responses during fictive cough and suggest a possible source of the N-D type of neuron for abdominal muscles during cough. [Jpn J Physiol 54 Suppl:S108 (2004)]
