Dekhuijzen A J, Iezzi N, Hurlbut W P
Department of Functional Anatomy, Free University, Amsterdam, The Netherlands.
Pflugers Arch. 1989 Sep;414(6):683-9. doi: 10.1007/BF00582136.
Lanthanum (La3+, 0.1-2mM) was applied to frog cutaneous pectoris muscles at 20-25 degrees C, or at 3-5 degrees C, and the mean amplitude and rate of occurrence, mean value of r, of the miniature endplate potentials (mepps) were measured as functions of time at single neuromuscular junctions. Some muscles were fixed at 3-5 degrees C and their nerve terminals examined in the electron microscope. When 1 or 2 mM La3+ was applied at room temperature, mean value of r rose to peak values of 0.8-3.4 x 10(3) and then declined to less than 100/s after 30-60 min. When the results are corrected for the dispersion in mepp amplitudes, we estimate that approximately 1.8 x 10(6) mepps occurred in this time. If 0.1 mM La3+ was applied, or if 1 mM La3+ was removed when mean value of r was near its peak, then mean value of r remained high for at least 1 h and approximately 4 x 10(6) mepps occurred. All these mepp counts exceed the 0.7 x 10(6) quanta stored in resting nerve terminals. When 1 or 2 mM La3+ was applied at 3-5 degrees C, mean value of r rose to peak values of 50-700/s and then fell to 20-200/s after 20-30 min. If the La3+ was then removed, mean value of r declined approximately 50% over the next hour; approximately 0.7 x 10(6) mepps occurred at the junctions treated with 1 mM La3+, and their terminals still contained about 69% of their vesicles. Thus, vesicles can be recycled at 3-5 degrees C. Millimolar concentrations of La3+ reduced the mepp amplitude by 70-80% at both temperatures and abolished almost completely the depolarization produced by bath applied acetylcholine or carbachol. These effects were reversible.
在20 - 25摄氏度或3 - 5摄氏度下，将镧（La3 +，0.1 - 2mM）施加于青蛙胸皮肌，在单个神经肌肉接头处，测量微小终板电位（mepps）的平均振幅、发生率以及r的平均值随时间的变化。一些肌肉在3 - 5摄氏度下固定，其神经末梢用电子显微镜检查。当在室温下施加1或2 mM La3 +时，r的平均值上升至峰值0.8 - 3.4×10³，然后在30 - 60分钟后降至低于100/s。当对mepp振幅的离散度进行校正后，我们估计在此期间大约发生了1.8×10⁶个mepps。如果施加0.1 mM La3 +，或者当r的平均值接近峰值时去除1 mM La3 +，则r的平均值至少1小时保持高位，并且大约发生4×10⁶个mepps。所有这些mepp计数都超过了静息神经末梢中储存的0.7×10⁶个量子。当在3 - 5摄氏度下施加1或2 mM La3 +时，r的平均值上升至峰值50 - 700/s，然后在20 - 30分钟后降至20 - 200/s。如果随后去除La3 +，r的平均值在接下来的一小时内下降约50%；在用1 mM La3 +处理的接头处大约发生了0.7×10⁶个mepps，并且其末梢仍含有约69%的囊泡。因此，囊泡在3 - 5摄氏度下可以循环利用。在两个温度下，毫摩尔浓度的La3 +使mepp振幅降低70 - 80%，并几乎完全消除了浴加乙酰胆碱或卡巴胆碱产生的去极化。这些作用是可逆的。
