[Morphological connections between the Hypoglassal and facial nerve in the brain stem of the rat].
OBJECTIVE
The perfect coordination and synchronization of hypoglossal and facial muscles during chewing, swallowing, breathing, and vocalization requires particular concomitant activities of the facial muscles. In contrast, no direct connection between the facial and hypoglossal nucleus on the level of the brain stem has been detected until now.


METHODS
Facial and hypoglossal nuclei of rats were identified on the basis of their antidromic field potential recorded after peripheral stimulation of the corresponding nerves. Stereotactically single or double fluorescence tracer injections (Biotin-Dextran, Fluorescine-Dextran, Rhodamine-Dextran, Fluoro Gold) were placed into the nuclei.


RESULTS
Retrograde tracer injections into the facial nucleus consistently labeled small neurons in the hypoglossal nucleus. In reverse experiments the injection of anterograde tracers into the hypoglossal nucleus labeled fine caliber varicose nerve fibers, but no somata in the facial nucleus. Synchronous injections of different tracers into the facial and hypoglossal nucleus produced a small, but constant number of double-labeled cells in the parvocellular reticular formation.


CONCLUSIONS
Both, hypoglossal interneurons projecting to the facial nucleus and neurons of the parvocellular reticular formation double-projecting to the facial and hypoglossal nucleus might play an important role in coordinated orofacial movements. Moreover, both populations of neurons might be responsible for the excellent postoperative results after hypoglossal-facial anastomosis.
Streppel
M
M
Klinik und Poliklinik für Hals-Nasen-Ohren-Heilkunde, Universität zu Köln, Joseph Stelzmann-Strasse 9, 50924 Köln. michael.streppel@uni-koeln.de
Popratiloff
A
A
Gruart
A
A
Angelov
D N
DN
Guntinas-Lichius
O
O
Delgado-Garcia
J M
JM
Neiss
W F
WF
Stennert
E
E
D000818:Animals; D001931:Brain Mapping; D001933:Brain Stem / Q000033:anatomy & histology*; D003679:Deglutition / Q000502:physiology; D005152:Facial Muscles / Q000294:innervation; D005154:Facial Nerve / Q000033:anatomy & histology*; D005260:Female; D007002:Hypoglossal Nerve / Q000033:anatomy & histology*; D008409:Mastication / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D012119:Respiration; D014828:Vocalization, Animal / Q000502:physiology
Morphologische Verbindungen zwischen N. hypoglossus und N. facialis im Hirnstamm der Ratte.