抄録
The larynx plays critical roles in respiration, vocalization, and several airway defensive reflexes. Functional roles of the vocal cord tensor in these behaviors are not well known. Intracellular recordings of cricothyroid muscle motoneurons (CTMs) were performed in 11 decerebrated and paralyzed cats during fictive respiration, vocalization, coughing, and swallowing. Intracellular application of continuous negative currents was attempted to confirm the presence of inhibitory postsynaptic potentials. All CTMs depolarized during the inspiratory phase of breathing; one half depolarized during the expiratory phase as well. During vocalization, CTMs rapidly depolarized at the onset of the vocal phase and retained strong depolarization throughout the vocal phase. During coughing, CTMs depolarized during the inspiratory phase, repolarized prior to the onset of the abdominal nerve burst, which was confirmed to exist inhibitory postsynaptic potentials, and then depolarized during the abdominal burst. During swallowing, most CTMs exhibited a hyperpolarization, sometimes followed by a weak depolarization, whereas some CTMs exhibited a slight depolarization. This study suggests that the main role of the vocal cord tensor is vocalization rather than airway defensive reflexes and that CTM activities are primarily generated by excitatory inputs during breathing and vocalization, while inhibitory inputs play an important role to control CTM activities during coughing and swallowing. [Jpn J Physiol 54 Suppl:S109 (2004)]
