Taylor R E, Bezanilla F, Rojas E
Biophys J. 1980 Jan;29(1):95-117. doi: 10.1016/S0006-3495(80)85120-4.
The Schwann cell, basement membrane, and connective tissue layers that surround the squid giant axon and constitute barriers to diffusion, were modeled in a number of ways to analyze various experimental results. The experiments considered are (a) the time-course of the potassium concentration in the space between the Schwann cell and the axon membrane (from now on referred to as the F-H space) after an initial loading, (b) the time-course of sodium concentration in the F-H space after a sudden change in the sodium concentration in the external fluid; (c) the time-course of the concentration of tetrodotoxin (TTX) or saxitoxin (STX) in the F-H space after a sudden change in external concentration, including (or not) the effects of specific binding of TTX or STX to sites on the axon membrane and nonsaturable binding to sites in the F-H space or in the spaces (clefts) between Schwann cells; (d) the effects of the F-H space, clefts, and diffusion into the clefts from the outside (from now on referred to as convergence into the clefts) on the measured series resistance.The analysis shows that (1) in no case is it necessary to include the effects of the convergence into the clefts from the outside; (2) in case a, the basement membrane, connective tissue layers, and the unstirred layer may be neglected, i.e., the clefts are rate limiting; (3) in case b the clefts may be neglected, i.e., the unstirred layer is rate limiting; (4) in most cases the clefts may be replaced by an equivalent thin diffusion barrier.
围绕鱿鱼巨大轴突并构成扩散屏障的施万细胞、基底膜和结缔组织层，通过多种方式进行建模，以分析各种实验结果。所考虑的实验包括：（a）初始加载后施万细胞与轴突膜之间空间（以下简称F-H空间）中钾离子浓度的时间进程；（b）外部液体中钠离子浓度突然变化后F-H空间中钠离子浓度的时间进程；（c）外部浓度突然变化后F-H空间中河豚毒素（TTX）或石房蛤毒素（STX）浓度的时间进程，包括（或不包括）TTX或STX与轴突膜上位点的特异性结合以及与F-H空间或施万细胞之间缝隙（裂沟）中位点的非饱和结合的影响；（d）F-H空间、裂沟以及从外部扩散到裂沟（以下简称汇聚到裂沟）对测量的串联电阻的影响。分析表明：（1）在任何情况下都无需考虑从外部汇聚到裂沟的影响；（2）在情况a中，基底膜、结缔组织层和未搅动层可忽略不计，即裂沟是限速因素；（3）在情况b中，裂沟可忽略不计，即未搅动层是限速因素；（4）在大多数情况下，裂沟可用等效的薄扩散屏障代替。
