L-甲状腺素钠对蟾蜍神经-肌肉传递的突触前影响

PRESYNAPTIC EFFFCT OF L-THYROXINE SODIUM ON NEUROMUSCULAR TRANSMISSION IN THE TOAD

在中华亚型大蟾蜍离体坐骨神经－缝匠肌制备的肌纤维终板，应用细胞内记录技术，研究了甲状腺素对神经－肌肉接头胆碱能传递的影响。结果表明：Ｌ－甲状腺素钠（５０μｍｏｌ／Ｌ）加入制备的浸浴液中，引起ｄ－筒箭毒处理标本的终极电位增高，但对高镁（１０ｍｍｏｌ／ＬＭｇＣｌ２）处理标本的终板电位无影响；也使小终报电位频率显著增加而振幅无明显改变，静息膜电位也不变。结果提示，Ｌ－甲状腺素钠能增强神经－肌肉传递，其起源可能是突触前的。

The effect of thyroxine on cholinergic transmission was studied in vitro with intracellular recording in the muscle fibers of sciatic nervesartorius muscle preparations of the toad (Bufo bufo gargarizans).The results showed that L-thyroxine sodium (50 μmol/ L), added to bath medium, caused an increase in endplate potentials (EPP) in preparations treated with d-tubocurarine but elicited no obvious effect on EPP in preparations treated with 10 mmol/ L MgCl2, and it also caused significant increase in frquency of miniature endplate potentials (MEPP) but not in amplitude of MEPP while the resting membrane potentials showed no changes. These results suggest that L-thyroxine sodium could increase neuromuscular transmission, and the effect seems to be presynaptic in nature.