Responses of Neurons in Paramedian Reticular Nucleus to Chemical Stimulations and Alteration of Blood Pressure in Rats

大白鼠旁中網狀核神經元對化學刺激及血壓改變之反應

林滿玉(A. M. Y. Lin) ； 王昀(Y. Wang) ； 蘇俊魁(C. K. Su) ； 李小媛(E. H. Y. Lee) ； 郭重雄(J. S. Kuo) ； 蔡作雍(C. Y. Chai)

《The Chinese Journal of Physiology》 34卷2期 (1991/06) Pp. 187-200

摘要

根據以往研究的結果，已知延腦旁中網狀核具有抑制交感神經和副交感神經活動的作用。本實驗以大白鼠為材料，主要利用兩種方法以證實旁中網狀核含有調節心臟血管功能的神經元。方法之一是利用化學刺激，即在旁中網狀核微量注射DL-homocysteic acid、乙醯膽鹼(acetyl-choline)及單胺類擬神經傳導素(monoamines)以激發心臟血管功能的反應；另一是利用單電極記錄旁中網狀核神經元的細胞外電位，並由靜脈注射乙醯膽鹼或正腎上腺素(norepinephrine)引發血壓改變，以觀察旁中網狀核神經元放電頻率改變的型式。結果發現，用電刺激旁中網狀核所引起的降血壓和輕微心跳變慢作用，與在旁中網狀核微量注射DL-homocysteic acid所引起的反應類似。進一步在旁中網狀核微量注射乙醯膽鹼、正腎上腺素或色胺酸(serotonin)，亦能激發類似的降血壓作用。從這項結果可以看出，上述的擬神經傳導素與旁中網狀核對心臟血管的調節功能可能有關。旁中網狀核神經元對血壓升降所引起放電頻率的變化可被區分為三類型：第一類型，25/69個神經元中，其放電頻率改變的方向與血壓改變的方向相同；第二類型，17/69個神經元中，其放電頻率改變的方向與血壓改變的方向相反；第三類型，27/69個神經元中，其放電頻率改變的方向與血壓改變的方向並無固定的關係。這三種類型的神經元都能被微量注射DL-homocsteic acod所興奮，而且其未瀘彼(unfilter)動作電位之持續期(duration)均大於0.5秒。這項結果顯示，上述三種類型的神經元均非聯絡性神經元(interneuron)，而且大部份的旁中網狀核神經元(42/69)都接受感壓反射的傳入訊息。

並列摘要

Lin, A.M.Y., Y. Wang, C.K. Su, E.H.Y. Lee, J.S. Kuo, and C.Y. Chai. Responses of neurons in paramedian reticular nucleus to chemical stimulations and alteration of blood pressure in rats Chinese J. Physiol. 34(2): 187-200, 1991. Previous studies have shown that paramedian reticular nucleus (PRN) possessed sympathetic and parasympathetic inhibitions on autonomic nervous system. In the present study, the cardiovascular reactions of PRN by locally-applied DL-homocysteic acid (DLH), acetyicholine (ACh), monoamines and electrophysiological properties of PRN neurons responding to intravenous injection of ACh and NE were studied in adult Sprague-Dawly rats. In PRN, electrical stimulation caused hypotension and mild bradycardia while micro- injection of DLH, which excites only cell body of the neurons but not passing fibers, evoked similar responses. Furthermore, direct application of ACh, norepinephrine (NE) or serotonin (5-HT) in PRN also produced hypotension, suggesting that these putative neurotransmitters may be involved in the cardiovascular responses in PRN. The electrophysiological properties of PRN neurons were studied: Neurons in PRN could be categorized into three types according to their neuronal activities in response to the changes of systemic arterial blood pressure (SAP) by ACh or NE given intravenously. Type Ⅰ neurons (25/69) were activated in the same direction of SAP changes. Type Ⅱ neurons (17/69) responded opposite to the direction of SAP changes. Type Ⅲ neurons (27/69) responded inconsistently to the changes of SAP. All the three types of neurons were excited by locally-applied DLH and possessed a similar unfiltered action potential duration of greater than 0.5 msec.

並列關鍵字

paramedian reticular nucleus ； raphe nucleus ； sympathetic inhibition ； baroreceptor reflex ； splanchnic nerve activities