Invited Symposium: Neural Mechanism of Mammalian Vocalization



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Neurophysiological and Pharmacological Studies of Vocal Motoneurons in the Nucleus Ambiguus

Yajima, Y (Department of Physiology, Hyogo College of Medicine, Japan)

Contact Person: Yukio Yajima (yajima@hyo-med.ac.jp)


The nucleus ambiguus is known to involve in multiple motor control such as vocalization, respiration and swallowing. Our former studies on vocalizing monkeys implicated a possible inhibitory influence on ambiguous neurons. However, only a limited number of studies have been devoted to understand the nature of this inhibition in laryngeal motoneurons or respiratory interneurons in the nucleus ambiguus. In order to determine whether this inhibitory connection was mediated by the GABAA receptor, its agonist muscimol and/or the antagonist bicuculline were applied iontophoretically to single ambiguous neurons using multibarrel electrodes. The laryngeal motoneurons in the nucleus ambiguus were defined by antidromic stimulation of the recurrent nerve. For a majority of the motoneurons, application of GABA and its antagonist or agonist affected the antidromic spikes in a dose-dependent manner. Respiratory neurons on the other hand exhibited rhythmic bursting activities usually time locked to the respiratory phases, and for the most part, were not antidromically driven by the nerve stimulation. Application of the antagonist to these neurons produced a remarkable facilitation in maximum discharge rate, whereas the agonist reversed this effect completely. The results were discussed in terms of the inhibitory synapse in the nucleus ambiguus and reciprocal inhibition in the laryngeal motor system.

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Presentation Number SAyajima0568
Keywords: nucleus ambiguus, motoneurons, GABA, iontophoresis, rats

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Yajima, Y; (1998). Neurophysiological and Pharmacological Studies of Vocal Motoneurons in the Nucleus Ambiguus. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/brudzynski/yajima0568/index.html
© 1998 Author(s) Hold Copyright