貓延腦吻端腹外側與疑核間神經徑路之電生理研究

Electrophysiological study of the neural projection from the rostral ventrolateral medulla to the nucleus ambiguus in cats

顧文欣(Wen-hsin Ku)

指導教授 ： 黃基礎

國立臺灣師範大學/理學院/生物學系/碩士(1999年)

摘要

本研究的目的是以逆向傳導鑑定（antidromic identification）來驗證延腦吻端腹外側（rostral ventrolateral medulla; rVLM）是否有神經纖維直接投射至疑核（nucleus ambiguus; NA）。以麻醉成貓為實驗材料，切斷兩側迷走神經，用肌肉麻痺劑麻痺後，以人工呼吸器維持其生命。在延腦吻端腹外側進行細胞外記錄（extracellular recording），當記錄到單一神經元神經訊號時，即在疑核給予電刺激，進行逆向傳導鑑定。
本研究記錄到的70個神經元中，49個是呼吸相關神經元，其中吸氣神經元（I）佔10%，呼氣神經元（E）佔27%，吸氣—呼氣神經元（IE）佔12%，呼氣—吸氣神經元（EI）佔12%，連續放電神經元（T）的比例最高，佔39%。在延腦吻端腹外側49個位置進行逆向傳導鑑定，有一個神經元可在疑核進行電刺激時激起逆向動作電位。其證據包括，以50 Hz電刺激能引發逆向動作電位，又能與正向動作電位相撞。有一個神經元在刺激後記錄到正向動作電位，另外還有15個記錄點能記錄到刺激後的誘發電位。此外，在對7個呼吸相關神經元進行提高呼氣末二氧化碳濃度的測試時，有6個有放電頻率增加的現象。
本研究結果顯示，貓延腦吻端腹外側可能有神經纖維投射至疑核，並藉此調控疑核中神經元的呼吸相關活動，進而影響自疑核起源的周邊神經呼吸活動。

關鍵字

延腦吻端腹外側 ； 疑核 ； 逆向傳導鑑定 ； 貓 ； 細胞外記錄

並列摘要

The purpose of the present study was to examine the existence of the neural pathway projecting from the rostral ventrolateral medulla (rVLM) to the nucleus ambiguus (NA) by a technique of antidromic identification. Adult cats were anesthetized with pentobarbital sodium (30 mg/kg, i.p.). Bilateral vagotomy, paralyzation, and artificial ventilation were performed. Animals were maintained at normocapnia or hypercapnia in hyperoxia. Single unit activity in the rVLM was explored extracellularly. Electrical current (0.3 ms pulse duration, 1 Hz, and a variety of current intensity) was delivered to the NA once a single rVLM unit was verified by displaying the same amplitude and shape of the action potential on the oscilloscope. Of the 70 neurons examined, 49 neurons showed respiratory-related discharge pattern (10% inspiratory, 27% expiratory, 12% inspiratory-expiratory, 12% expiratory-inspiratory, and 39% tonic). Of the 49 recording sites tested, 1 unit could be activated antidromically by the delivery of current to the NA. This antidromic spike followed a 50 Hz repetition rate and could be collided with an orthodromic spike. Another unit could be activated orthodromically from the NA. In addition, there were evoked potentials in 15 recording sites. Moreover, 6 of the 7 respiratory-related neurons examined showed a tendency to increase their discharge rate in response to hypercapnia in hyperoxia.
The present results demonstrate that the neurons in the rVLM may send axonal projections to the NA. These neural pathways may modulate the respiratory-related neuron activities in the NA which, in turn, influence the respiratory-related activities of the peripheral nerves originating from the NA.

並列關鍵字

rostral ventrolateral medulla ； nucleus ambiguus ； antidromic identification ； cats ； extracellular recording

參考文獻

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