Dedicated to our honored teacher Dr. M. S. Davidoff, Professor at the Department of Anatomy, University of Hamburg, on the occasion of his 60th birthday.
Hypoglossal and reticular interneurons involved in oro-facial coordination in the rat †
Article first published online: 4 APR 2001
Copyright © 2001 Wiley-Liss, Inc.
Journal of Comparative Neurology
Volume 433, Issue 3, pages 364–379, 7 May 2001
How to Cite
Popratiloff, A. S., Streppel, M., Gruart, A., Guntinas-Lichius, O., Angelov, D. N., Stennert, E., Delgado-García, J. M. and Neiss, W. F. (2001), Hypoglossal and reticular interneurons involved in oro-facial coordination in the rat . J. Comp. Neurol., 433: 364–379. doi: 10.1002/cne.1145
- Issue published online: 4 APR 2001
- Article first published online: 4 APR 2001
- Manuscript Accepted: 29 JAN 2001
- Manuscript Revised: 15 DEC 2000
- Manuscript Received: 10 MAY 2000
- The Jean Uhrmacher Foundation
- Acciones Integradas Hispano-Alemanas (DAAD and Dirección General de Investigación Cientifica y Técnica)
- Verfügungsfond der Medizinischen Fakultät der Universität zu Köln
- Megapharm GmbH
- COST B10
- oro-facial coordination;
- hypoglossal nucleus;
- facial nucleus;
- hypoglossal internuclear interneurons
Chewing, swallowing, breathing, and vocalization in mammals require precise coordination of tongue movements with concomitant activities of the mimetic muscles. The neuroanatomic basis for this oro-facial coordination is not yet fully understood. After the stereotaxic microinjection of retrograde and anterograde neuronal tracers (biotin-dextran, Fluoro-Ruby, Fluoro-Emerald, and Fluoro-Gold) into the facial and hypoglossal nuclei of the rat, we report here a direct bilateral projection of hypoglossal internuclear interneurons onto facial motoneurons. We also confirm the existence of a small pool of neurons in the dorsal part of the brainstem reticular formation that project ipsilaterally to both facial and hypoglossal nuclei. For precise tracer injections, both motor nuclei were located and identified by the electrical antidromic activation of their constituent motoneurons. Injections of retrograde tracers into the facial nucleus consistently labeled neurons in the hypoglossal nucleus. These neurons prevalently lay in the ipsilateral side, were small in size, and, like classic intrinsic hypoglossal local-circuit interneurons, had several thin dendrites. Reverse experiments — injections of anterograde tracers into the hypoglossal nucleus — labeled fine varicose nerve fiber terminals in the facial nucleus. These fiber terminals were concentrated in the intermediate subdivision of the facial nucleus, with a strong ipsilateral prevalence. Double injections of different tracers into the facial and the hypoglossal nuclei revealed a small, but constant, number of double-labeled neurons located predominantly ipsilateral in the caudal brainstem reticular formation. Hypoglossal internuclear interneurons projecting to the facial nucleus, as well as those neurons of the parvocellular reticular formation that project to both facial and hypoglossal nuclei, could be involved in oro-facial coordination. J. Comp. Neurol. 433:364–379, 2001. © 2001 Wiley-Liss, Inc.