ラット顔面筋支配の顔面神経求心性信号と反射

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Present study was carried out to investigate the jaw muscles activated by an electrical stimulation to branches of the facial nerve innervating the facial muscles in the urethane-chloralose anesthetized rat. An electrical stimulation was applied to the branches of the facial nerve : the temporal, zygomatic, buccal, and marginal mandibular branch respectively. These branches were cut off in peripheral portion. Evoked EMGs were recorded at the anterior belly of the digastric, mylohyoid, and masseter muscle. Reflex discharges were recorded from the mylohyoid branch of the trigeminal nerve. Furthermore, afferent responses of the facial nerve were recorded by mechanical stimulation to the facial muscles. The main findings were summarized as follows. 1. When an electrical stimulation was applied to the buccal and marginal mandibular branch of the facial nerve respectively, evoked EMG was recorded from the anterior belly of the digastric muscle. In this case, the evoked EMG elicited by a stimulation of the buccal branch was greater and generated by a lower strength of stimulation than that in the marginal mandibular branch. In this evoked EMG, two types of reflex discharges, fast and slow reflex discharges were observed. Fast reflex discharges had latencies of 16.8-20.0 msec and disappeared in a short time. Slow reflex discharges had a latency of about 300 msec and lasted for a long time. Both reflex discharges increased in frequency and amplitude to maximum with an increase in the stimulus strength. No discharge was elicited by an electrical stimulation to the temporal and zygomatic branch. 2. These reflex discharges disappeared after pinching a point at the central side of the stimulating point in the buccal and marginal mandibular branch with a pincette. 3. Evoked EMG was generated in the mylohyoid muscle by an electrical stimulation to the buccal branch of the facial nerve. In this case, two reflex discharges, fast and slow reflex discharges similar to those observed at the anterior belly of the digastric muscle were recognized. 4. Reflex discharges were generated in the mylohyoid branch of the trigeminal nerve by an electrical stimulation to the buccal branch of the facial nerve. In these reflex discharges, fast and slow reflex discharges were observed also. 5. No reflex discharge was generated in the masseter muscle by an electrical stimulation to the buccal branch in most preparations. In only 2 cases out of 19 cases, small reflex discharges were recognized. 6. When tactile and pressure stimulation were applied to the surface of the facial muscle in the buccal region, afferent impulses were elicited in the buccal and marginal mandibular branch. In these afferent impulses, two or three types of units : fast, slow and intermediate adapting units were observed to exist in these branches. 7. The receptive fields caused to these afferent discharges were a narrow area on the surface of the facial muscles in the perioral and buccal region.
九州歯科学会の論文

ラット顔面筋支配の顔面神経求心性信号と反射

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