微小终板电流的上升时间表明乙酰胆碱可能在一段时间内释放。
The rise times of miniature endplate currents suggest that acetylcholine may be released over a period of time.
作者信息
Van der Kloot W
机构信息
Department of Physiology and Biophysics, State University of New York, Stony Brook 11794, USA.
出版信息
Biophys J. 1995 Jul;69(1):148-54. doi: 10.1016/S0006-3495(95)79884-8.
Models of miniature endplate currents predict 20-80% rise times of 100 microseconds or less. These predictions are substantially less than most of the rise times recorded in the literature. New measurements were made of rise times at the frog neuromuscular junction using extracellular recording. The mean 20-80% rise time was 250 microseconds. Rise times were variable; at 20 degrees C, 95% of them fell in a range from 140 to 460 microseconds. The most questionable assumption in the models is that the acetylcholine (ACh) is released instantaneously. Modifying the model, so that ACh diffuses from the vesicle through a pore, lengthens the rise time to observed levels. It has been proposed that ACh is released from the vesicle in exchange for Na+. However, the rise times of miniature endplate currents recorded in solutions in which the Na+ is replaced by sucrose are in the normal range. The Q10 for the rise of miniature endplate currents is approximately 2, which is consistent with the models and with temperature effects on pore formation in mast cells.
微型终板电流模型预测20 - 80%的上升时间为100微秒或更短。这些预测结果远低于文献中记录的大多数上升时间。利用细胞外记录对青蛙神经肌肉接头处的上升时间进行了新的测量。20 - 80%的平均上升时间为250微秒。上升时间是可变的；在20摄氏度时，95%的上升时间在140至460微秒范围内。模型中最值得怀疑的假设是乙酰胆碱（ACh）是瞬间释放的。对模型进行修改，使ACh从囊泡通过一个孔扩散，可将上升时间延长至观察到的水平。有人提出ACh从囊泡中释放以交换Na+。然而，在Na+被蔗糖取代的溶液中记录的微型终板电流的上升时间处于正常范围内。微型终板电流上升的Q10约为2，这与模型以及温度对肥大细胞中孔形成的影响是一致的。
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