• 作者： 蘇銘嘉; 張傳?
• 作者服務機構： 國立臺灣醫學院藥理學研究所
• 中文摘要： Notexin係由Notechis scutatus分離之單?鏈鍵前神經毒素，本實驗研究鍶離子及其它兩價陽離子對Notexin之磷
  脂?甲活性以及其神經－肌傳導阻斷作用之影響，同時與其它多?鏈鍵前神經毒素作比較。在鎂離子或鈣離子存在下
  Notexin之磷脂?甲活性受到完全活化，但鍶離子則會抑制Notexin之磷脂?甲活性以及其神經－肌傳導阻斷作用，此種
  鍶離子對Notexin之對抗作用比其對β-Bungarotoxin及Crotoxin之對抗作用不明顯。在小白鼠中，Notexin對年幼之小
  白鼠之作用比其對年長之小白鼠之作用強。與Taipoxin及Crotoxin一樣，大花鼠對Notexin之敏感度較差。在小雞雖然其
  對β-Bungarotoxin與Crotoxin特別敏感，但其對Notexin之敏感度與小白鼠相似。在離體小白鼠膈神經-肌標本，在浸浴
  於含鍶或鎂-Tyrode液下時，則Notexin對神經刺激所引起之收縮反應以及終板電位之量子數會立刻引起明顯之抑制作用
  ，但在此初期抑制作用後並沒有加強作用產生。但是在青蛙或大花鼠之神經-肌標本中則Notexin對神經傳遞物質釋放之
  量子數在初期抑制作用後立刻有加強作用產生。高鈣、高鎂或低鈣溶液均會對抗Notexin在小白鼠之神經-肌傳導之阻斷
  作用。與其他鍵前神經毒素一樣神經刺激頻率之增加會加強Notexin對神經-肌傳導之阻斷作用，此加強作用在含鍶溶液中
  比在含鈣溶液中較不明顯。由以上結果可知Notexin可能與其它蛇毒分出之鍵前神經毒素一樣對神經末梢可能有很高之親
  和力，在其與神經末梢結合後可能會經由其磷脂?活性而分解神經軸膜上之磷脂類而阻斷神經-肌傳導。但初期之抑制作用
  可能是因毒素分子與神經結合所產生之結果。
  以
• 英文摘要： The presynaptic effects of notexin, a single unit toxin isolated from the venom of Notechis scutatus,were compared with those of other presynaptic toxins which are composed of two or more units or chains.The effects of (方程式無法摘錄) and other bivalent cations on the immediate and delayed presynaptic effects and phos-pholipase A activity were also compared. The phosuholipase A activity of notexin was fully activated by (方程式無法摘錄) and (方程式無法摘錄) . (方程式無法摘錄) inmbiten the enzymatic as well as the neuromuscular blocking activity or riotexinthough to a lesser extent than did β-bungarotoxin and crotoxin. Young mice were more sensitive to notexinthan older ones. Like taipoxin and crotoxin, notexin was much less potent in blocking rat muscle, but un-like β-bungarotoxin and crotoxin, was not particularly effective on chick muscle, In the isolated mousephrenic-nerve diaphragm preparation immersed in (方程式無法摘錄) or high (方程式無法摘錄) -Tyrode, notexin caused immediatedepression of the twitch response and the quantal contents of e.p.p.s without appreciable subsequent faci-Illation. By contrast, in the isolated frog sartorius and the rat and mouse diaphragm muscles, notexin causedan immediate reduction of quantal contents followed by a facilitation of the transmitter-release. High con-centration of (方程式無法摘錄) , high concentration of (方程式無法摘錄) , or low concentration of Cat＋were all antagonistic to theprogress of presynaptic inhibitory action of notexin in the mouse preparation. Like all other presynaptictoxins, the acceleration of presynaptic block by an increase of nerve stimulation was less prominent in themedium in which (方程式無法摘錄) was replaced wit (方程式無法摘錄) . Notexin, like other presynaptic neurotoxins of snake venomorigin, caused presynaptic failure by its high affinity for the nerve terminal and subsequent hydrolysis ofphospholipids in the axolemma. The immediate presynaptic depression, however, appears to be due to thebinding of the toxin molecule per se.
• 中文關鍵字： Notexin-Phospholipase A2-Neurotoxins-Snake venoms-Presynaptic effect.
• 英文關鍵字： --