• 作者： 李鎮源；蔡明正
• 作者服務機構： 國立臺灣大學醫學院藥理學研究所
• 中文摘要： 本文詳細分析比較由印度雨傘節蛇(Bungarus caeruleus)分離、精製之二種神經毒素（I-B-2及III-Α)之藥理作用。在大老鼠橫隔膜神經肌標本，I-B-2抑制神經肌傳導作用之速率與其劑量有關，但與刺激神經之電流頻率無關。III-A.之作用，縱使 使用大量，必須超過100分鐘才能產生抑制神經肌傳導之作用，而其作用與刺激神經之電流頻率有關。箭毒(d-tubocurarine) 可以抑制I-B-2與乙醯膽酯感受體之結合反應，但它無法對抗III-A對神經肌傳導之作用。 III-A先增加了微小終板電位之頻率，後則抑制微小終板電位之?生。將III-A注射入小白鼠之腹腔經60?90分鐘時 其膈神經末端之軸膜上有Ω型胞囊。小白鼠呼吸停止時，其膈神經末端內之胞囊幾乎完全消失，粒腺體也有膨脹產生空 泡之現象。若將I-B-2注射入小白鼠之腹腔，至其呼吸停止時，其膈神經末端之型態與正常比較，則無顯著之變化。 這些現象顯示III-A係一種鍵前毒素，與臺灣雨傘節蛇毒內之β-bungarotoxin之作用相似，而I-B-2則屬於鍵後毒素 與台灣雨傘節蛇毒內之α-bungarotoxin作用相似。
• 英文摘要： Pharmacological properties of two neurotoxins (I-B-2 and III-A) isolated from the venom of Bungarus caeruleus are compared. In the rat phrenic nerve-diaphragm preparation, the neuromuscular (N-M) blocking action of I-B-2 is dose dependent, whereas a period of more than 100 min is required for n-M block by III-A even at high concentrations. The time for n-M block is dependent on the rate of nerve stimulation for III-A but not for I-B-2. The interaction of I-B-2 with the acetylcholine receptor in the motor endplate is prevented by D-tubocurarine, whereas no prevention is found against the action of III-A. The spontaneous miniature endplate potential (MEPP) is at first increased in frequency, then gradually decreased and finally abolished by III-A. Sixty to 90 min after i. p. injection of III-A (0.2 μg/g) into mice, numerous omega-snaped fusing vesicles are observed along the axolemma of the phrenic nerve terminal. At the time of respiratory arrest, the synaptic vesicles in many axon terminals are almost completely depleted, and swelling and vacuolization of mitochondria are observed. No such ultrastructural changes are found with I-B-2. These findings indicate that III-A is a presynaptic toxin similar to β-bungarotoxin, whereas I-B-2 is a postsynaptic toxin similar to a-bungarotoxin.
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