[Brainstem segmental arrangement of sucking rhythm generators for trigeminal, facial and hypoglossal motoneurons].
Rhythmical sucking like activity (RSA) is known to be induced in the hypoglossal nerve (XII n) in an isolated brainstem-spinal cord preparation from newborn rats with bath application of N-methyl-D-aspartate (NMDA). Since natural sucking consists of well-coordinated rhythmical activities of the tongue, face, and jaw muscles, it is assumed that the trigeminal (V) and facial (VII) motoneurons would show rhythmical activities during the RSA. The purpose of this study was (1) to induce rhythmical activities in the V and VII ns in addition to XII n during bath application of NMDA, and (2) if they are induced, to locate the structures essential for generation of NMDA-induced rhythmical V, VII, and XII n activities using sectioning techniques. Experiments were performed on brainstem-spinal cord preparations isolated from newborn mice with or without the orofacial structure. Neural activities were recorded from the V, VII, and XII ns with suction electrodes. Movements of the tongue and jaw were recorded with a CCD camera system. It was found that (1) bath application of NMDA (5-20 microM) induced RSA in the V, VII, and XII ns, (2) it also induced rhythmical sucking-like movements of the jaw and tongue, and (3) after complete transections of the brainstem between the V and VII ns as well as at the pontomedullary junction, NMDA still induced the RSA in the V, VII, and XII ns. These results demonstrate that separate rhythm generators for rhythmical NMDA-induced activities in the V, VII, and XII motoneurons are located at the respective levels in the brainstem.
Nakajima
M
M
Department of Physiology, Faculty of Dentistry, Tokyo Medical and Dental University.
D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000502:physiology*; D005154:Facial Nerve / Q000502:physiology*; D007002:Hypoglossal Nerve / Q000502:physiology*; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D009046:Motor Neurons / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D013391:Sucking Behavior / Q000502:physiology*; D014276:Trigeminal Nerve / Q000502:physiology*
D016202:N-Methylaspartate