乙型雨傘節蛇毒毒素（beta-bungarotoxin, beta-BuTx），由兩個次單元（subunit）所組成，分別是具有磷脂脢甲活性的A chain與B chain，現已證實

beta-Bungarotoxin (beta-BuTx), the presynaptic neurotoxin purified from the venom of Bungarus multicinctus, consists of two dissimilar polypeptide subunits. A phospholipase A2 subunit named A chain, and a non-phospholipase A2 subunits named B chain. The A chain and B chain are covalently linked by one disulfide bridge. Although it has been widely accepted that the toxic effect of beta-BuTx is attributed to the disturbance of presynaptic transmitter release, however the inhibition of transmitter release by beta-BuTx is still obscure. Here we investigate the mechanism that mediates facilitation of transmitter release at the neuromuscular junction induced by beta-BuTx, using Xenopus nerve-muscle coculture.
Application of beta-BuTx and isotoxins BM12, BM13 led to a marked increase in the frequency of spontaneous synaptic currents (SSCs) after a short period (12~18 min) of latency. The synaptic potentiation induced by these toxins was abolished when Ca2+ in the medium is substituted by Ba2+ (a potent phospholipase A2 inhibitor). Application of PLP-BM12 and PLP-BM13, which have been chemical-modification to lose their PLA2 activity from BM12 and BM13, failed to potentiate the transmitter release.

縮 寫 表 ……………………………………………… 1
中文摘要 ……………………………………………… 2
英文摘要 ……………………………………………… 5
緒 論 ……………………………………………… 7
實驗材料 ……………………………………………… 20
1. 爪蟾的神經、肌細胞共同培養…………… 20
2. 小雞二頸肌………………………………… 22
實驗方法 ……………………………………………… 24
1. 電生理記錄方法…………………………… 24
2. GDP-beta-S presynaptic nerve loading.25
3. 小雞二頸肌實驗……………………………26
4. 實驗數據之統計分析………………………27
5. 實驗用試劑及供應者……………………… 27
實驗結果 ……………………………………………… 29
討 論 ……………………………………………… 39
參考文獻 ……………………………………………… 45
圖 表 ……………………………………………… 56

Abe, T., Alema, S., and Miledi, R. (1977a) Phospholipase activity in