嚥下運動時の口蓋帆挙筋の収縮様式を解明する目的で, 内枝に電気刺激を与えることにより, 反射性嚥下動作を誘発し, その時の口蓋帆挙筋の等尺性収縮を記録, 分析するとともに, 筋電図活動と対比観察した.
1)内枝に単0電気刺激を与えることにより誘発された口蓋帆挙筋の等尺性収縮の収縮開始時点から最大張力の得られるまでの時間は45±3.1msec, 最大張力を示す時点から張力が半減するまでの時間は32±1.8msecであり, 刺激時点から反射性誘発筋放電および張力波形発現までの潜時は, それぞれ20±1.2msec, 27±1.9msecであった.
2)刺激頻度10Hz以上の反復電気刺激によって反射性嚥下運動が惹起され, 嚥下回数は, 30Hzの刺激頻度で最も多く認められた.
3)反射性嚥下運動時の口蓋帆挙筋からの筋放電は, 397±50msecの間観察され, 筋放電の発現は, 顎二腹筋前腹および顎舌骨筋よりも早期に認められた.
4)反射性嚥下運動時に認められた口蓋帆挙筋の張力曲線は, 0峰性で, 収縮力は張力発生後187±19msecで急激に減弱した.

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咽頭・喉頭領域の感覚神経（舌咽神経咽頭枝や）は，舌領域を支配する味覚神経（鼓索神経や舌咽神経舌枝）と異なる生理学的特徴をもっている．咽頭・喉頭領域の感覚神経は舌領域の味覚神経に比べ，味刺激（4基本味）に対して神経応答性は低いが，水やアルコール刺激に高い興奮性を示す．また，長鎖脂肪酸やうま味も咽頭・喉頭領域の感覚神経を興奮させる．このような舌の味覚神経とは異なる咽頭・喉頭領域の感覚応答特性が，食べ物や飲み物の「おいしさ」に重要な要素である「のどごし」や「こく」の感覚形成に関与している可能性が考えられる．様々な機能を有するtransient receptor potential（TRP）チャネルファミリーに注目すると，カプサイシンによって活性化するTRPV1が属するTRPVファミリーは，機械刺激，熱刺激，pHの変化，浸透圧の変化で活性化する．また，細胞の代謝，分化，増殖などに関係しているTRPMファミリーには，冷刺激やメントール刺激で活性化するチャネルがある．したがって，咽頭・喉頭領域に発現しているTRPチャネルが，飲食物を飲み込むときの味，温度，触，圧などの刺激を受容し，「のどごし」や「こく」の感覚形成に寄与していると考えられる．近年，嚥下中枢において，CB1受容体が興奮性シナプス群より抑制性シナプス群に多数存在することが明らかにされた．これらシナプス前終末のCB1受容体に内因性カンナビノイド（2-AG）が結合すると，神経伝達物質の放出が抑圧される．その結果，興奮性シナプスの作用が優位になり，嚥下誘発が促進する可能性が示唆された．このように咽頭・喉頭領域からの求心性情報は「おいしさ」の感覚に貢献し，さらに，生命活動に重要な摂食機能である嚥下反射の誘発にも深く関与している．


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近年，デバイスを用いて神経を刺激することで疾患の治療に役立てる「ニューロモデュレーション治療」が注目されている．最近，麻酔下ラットにおける

（SLN）への微弱な電流での電気刺激は，甲状腺からのカルシトニン分泌を促進することが示された．カルシトニンは破骨細胞に作用し骨吸収を抑制するホルモンである．この発見を骨粗鬆症に対する新しいニューロモデュレーション治療へつなげるためには，意識下動物におけるSLN刺激の安全性やカルシトニン分泌への作用，さらには，慢性的刺激が骨粗鬆症モデルラットの骨密度に及ぼす効果を確かめる必要がある．本稿ではこれらに関する我々の研究成果を紹介する．

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咽頭・喉頭領域の機械刺激および喉頭領域を神経支配しているの電気刺激は, 嚥下誘発に有効である.しかしながら咽頭領域を神経支配している舌咽神経の電気刺激は, に比べ嚥下誘発が困難であるといわれている.このことは嚥下に関するパラドックスと呼ばれており, 未だに解決していない.今回の研究の目的は, このパラドックスを解明することである.
咽頭・喉頭領域の嚥下誘発部位および神経支配を調べたところ, 機械刺激による嚥下誘発の高感受性部位は, 口蓋咽頭弓, 軟口蓋の後縁, 喉頭蓋の咽頭側外縁, 披裂喉頭蓋ヒダなどであり, これらの部位のうち, 口蓋咽頭弓, 軟口蓋の後縁は, 舌咽神経咽頭枝の切断の後, 嚥下誘発がなくなることから, 舌咽神経咽頭枝支配であることが判った.電気生理学的実験の結果は, 舌咽神経咽頭枝の電気刺激は, の電気刺激と同程度の嚥下誘発効果であったが, 舌咽神経舌枝の電気刺激は嚥下誘発に効果がなかった.また, 舌咽神経咽頭枝との同時刺激は嚥下誘発の促通を生じ, 舌咽神経舌枝との同時電気刺激は嚥下誘発を抑制した.これらの結果より, 舌咽神経のうち咽頭枝が嚥下誘発に重要な役割を果たしており, 舌枝は嚥下誘発に重要でないことが判った.パラドックスが生じた理由として, 過去の研究では舌咽神経舌枝のみ, あるいは舌咽神経舌枝と咽頭枝を同時に刺激していたのではないかと考えられる.

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After denervation of the recurrent laryngeal nerve (RLN), the innervated laryngeal muscles are atrophied. We have reported that functional electrical stimulation (FES) delivered to the thyroarytenoid (TA) muscle prevents muscle atrophy after denervation. The reason why FES prevents atrophy of the muscle is not yet clear.
In this study, we tried investigating a hypothesis that the superior laryngeal nerve (SLN) might have a role in preventing muscle atrophy by FES. We used 23 adult rats in this study. Resections of the left SLN with the left RLN, or bilateral SLNs with the left RLN were performed. A pair of thin wire stimulation electrodes (50 u m) was placed in the left TA muscle. The animals were divided into two groups : a stimulated group and a non-stimulated group. In the stimulated group, FES, with 2 mA rectangular pulses of 0.2 ms duration at 2 Hz lasting for 1 hour, was delivered to the TA muscle once every 2 days. After the stimulation periods of 2 or 4 weeks, frontal sections of the larynx 8 pm in thickness were prepared. The differences in the area of the TA muscle, the area of the TA muscle fiber and the density of the TA muscle fiber were compared between the denervated (left) side and the non-denervated (right) side.
Atrophy of the TA muscle was observed in spite of the ipsilateral and/or bilateral denervation of the SLN. The effect of FES to prevent muscle atrophy was also observed regardless of SLN resection. The results obtained from this study suggested that the information to the central nervous system through the SLN was not indispensable for preventing muscle atrophy after denervation of RLN.

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Recently, various effects of low power laser have been reported. Clinical application of Gallium Alminium Arsenide (Ga-Al-As) diode laser was developed and applied on several diseases.
On the other hand, quite frequently the otolaryngologist sees patients with abnormal sensations of the larynx. However, treatment for such disease still remain because this disease is eviked by complex local and general etiology. We paled attention to that disorders of sensory function and autonomic regulation in the larynx might result in such abnormal sensations of the larynx. In this study, we applied the low power Ga-Al-As diode laser irradiation for this disease. Therefore, we suggested that this laser irradiation technique was effective for this disease.
We previously reported on evoked potentials elicited by electrical stimulation of the superior laryngeal nerve as a reflection of activities in the brain stem and cortex in anesthetized cats. This evoked potential was named LSEP (Laryngeal Sensory Evoked Potential). We observed the influence of laser irradiation to superior laryngeal nerve using the LSEP technique, and suggested that this laser irradiation had some effects on the laryngeal sensory system.

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Sensory stimuli to the larynx evoke a laryngeal adductor reflex mediated by the brain stem via superior and recurrent laryngeal nerve. There are some reports that abnormal laryngeal reflex results in disorders of phonation and respiration. The clinical use of Larynx-evoked Brain Stem Response (LBR) as a research tool to study polysynaptic reflex pathway is considered to have a great advantage. The purpose of this report is to review the literature concerning LBR and to speculate the clinical application of LBR. In present time, there are detailed reports of LBR about validity of response, latencies, generator sources, on cat. However, there are a few reports of adaptation for use in humans.

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A pair of stainless steel electrodes were directly attached to the right internal branch of the superior laryngeal nerve (SLN) of a patient, on an occasion of total laryngectomy under general anesthesia. Square-wave electric stimuli were applied to the SLN, and the evoked electro-myographic signal (EMG) was picked up from the left cricothyroid muscle with a hooked-wire electrode. The larynx-evoked brain stem response (LBR) was also recorded via surface electrodes attached the skin of the head.
These evoked signals were averaged with a signal averaging computer. A two-phasic evoked EMG waveform was obtained with a latency of about 18 msec. An LBR wave with 3 positive peaks and 4 negative peaks was invariably derived corresponding to the stimuli, with a latency of about 3.5 msec. These data apparently demonstrated the existence of LBR in man.
Based on these findings, a clinically applicable method of obtaining LBR signal was devised. A hooked-wire electrode for stimulation was placed percutaneously in the vicinity of the SLN in 9 normal subjects. The cricothyroid EMG was recorded with another hooked-wire electrode. The position of the stimulating electrode was adjusted by monitoring the evoked EMG waveform on the CRT screen. The LBR signal was recorded via the surface electrodes. A similar LBR waveform as stated above was obtained. The clinical importance of recording LBR was emphasized.

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The glottis closes during not only cough reflex but also sneezing. It indicates that the activity of laryngeal motor neurons within the nucleus ambiguus is influenced by both the superior laryngeal and the trigeminal afferents. In this study, the convergence of inputs originated from the superior laryngeal and the anterior ethmoidal nerves is examined in decerebrate cats. Thirty two neurons are activated orthodromically by ipsilateral stimulation to the superior laryngeal nerve. Fifty eight neurons are activated orthodromically by ipsilateral stimulation to the anterior ethmoidal nerve. These two neuronal groups are overlapped each other in the nucleus reticularis parvicellularis of medulla. However, the neurons receiving afferents from the superior laryngeal nerve tend to exist in the dorso-lateral portion of the nucleus, while the neurons receiving afferents from the ethmoidal nerve tend to exist in the medio-ventral portion. Seven neurons receive afferents from both nerves. Most of these neurons are located in the overlapped area of two neuronal groups, which is apart from the nucleus ambiguus. The projectional pattern that different inputs converge into the reticular neurons outside of the nucleus ambiguus can be useful for evoking the adequate airway reflex related to the larynx.

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Eleven adult cats were anesthetized with intramuscular injection of Ketamine hydrochloride. Electrically induced vocalization was performed after Kanai's methode. (stimulating location APO, L4.5-5.5, H-3.5-6.0) The internal branch of the superior laryngeal nerve was cut and the peripheral stump was placed on a pair of silver recording electrodes. Then afferent discharges from laryngeal sensory receptors during electrically induced vocalization were recoded.
In this study, 16 single afferent discharges were obtained. They were classified into four groups. Discharge rate of the first group corresponded to the fundamental frequency change during evoked vocalization. Discharge rate of the second group showed augmentation during evoked vocalization but was not correlated with the fundamental frequency change. Discharge rate of the third group decreased during evoked vocalization. Receptors of the fouth group showed activities only at the initiation time of the evoked vocalization.
In 3 out of 7 successfully investigated cases, we observed that the pitch of evoked vocalization decreased after section of the internal branch of the superior laryngeal nerve. In the other cases, we observed hoarseness and an increase of the induced vocalization cycle.
These results suggest that central nerve system receives real time informations from the larynx during evoked vocalizatios and laryngeal sensory receptors play some role in the control mechanism of phonation.

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We reported previously that when the internal branch of the superior laryngeal nerve (ISLN) of generally anesthetized cats was electrically stimulated, short latency response (early response, ER) and long latency response (late response, LR) emerged in the thyroarytenoid muscle (TA). Vibratory stimulation, applied to the contralateral subglottic mucosa as a conditioning stimulation, enhanced LR, particularly in phase I (the transitional phase from inspiration to expiration). When the vibratory frequency was elevated from 100 Hz to 350 Hz at 50 Hz interval in phase I, vibration effect was observed in all frequencies investigated. Maximum effect was obtained at 300 Hz. Following denervation of ISLN, the vibration effect was minimized, and it did not depend on the vibratory frequency.
In the present study, the data processing technique was partly modified : the sampling time of integrated EMG of LR was shortened. As a result, LR was occasionally divided into two responses L₁R and L₂R. The effect of vibratory stimulation on the subglottic mucosa differed for L₁R and L₂R.
The effect of subglottic vibration upon LR as a function of vibratory frequency may reflect frequency characteristics of the mechanoreceptors to vibration in the subglottic mucosa. If this is the case, the aforementioned results indicate that there are two groups of mechanoreceptors having different frequency characteristics against vibration. The mechanoreceptors in the laryngeal mucosa play an important part in auto monitoring systems of vibration.

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「のど越し」という言葉はしばしば使われるがその実体はかなり複雑な感覚である。のど越しスッキリとかキレがいいと言う時とそうではない時とでは咽頭・喉頭からの神経情報にどのような違いがあるのであろうか。咽喉頭の味覚情報を担うと舌咽神経咽頭枝は水の刺激に対して高い応答性を示すという特徴がある。この両神経が顕著なのど越しの感覚を誘起するビール、炭酸水、吟醸酒などに対して特徴的な応答パターンを示すという最近の知見を紹介し、「のど越し」との対応について述べた。

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