Electrophysiological analysis of the lateral reticular formation subserving autonomic and motor oral functions

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Neural network in the brainstem subserving autonomic and motor oral functions was investigated by anatomical, electrophysiological and behavioral studies. In the anatomical study, horseradish peroxidase was injected into the anterior part of the tongue or the chorda-lingual nerve and the superior salivatory (SS) neurons innervating the tongue and those innervating the submandibular and sublingual salivary glands were identified in rats. The two groups of SS neurons were similar in shape and intermingled in the lateral reticular formation. In the electrophysiological study, biophysical properties of the SS neurons were analyzed by the whole-cell patch clamp technique in sliced brainstem preparations. The SS neurons innervating the tongue displayd a prominent transient outward current (A-current), and fired up to 70 Hz. Those innervating the salivary glands expressed A-current lasting longer period, and fired up to 30 Hz. In behavioral study, salivary flow from the submandibular gland an … More d activity of the masseter muscle were chronically recorded from the freely moving rats. During chewing, the amount of saliva and muscle activity were not always parallel, suggesting different centrifugal effects on autonomic and motor functions. When rejectable taste substance was injected into the mouth, a rhythmical muscle activity was induced accompanying vigorous salivation. This behavior also occurred in decerebrate animals, suggesting that the reflex are of this behavior is situated in the lower brainstem. When salivary glands were extirpated, the jaw movement during chewing became irregular and taste sensitivity of the chorda tympani nerve decreased.Though these studies, we conclude that the autonomic and motor oral functions are under control from the higher central nervous system, but there is a contact point between the two functions in the lower brainstem especially the lateral reticular formation. The activity of the pre-motor neurons of the trigeminal motor nucleus should be analyzed and compared with that of the SS neurons. Less