Inactivation of sodium channels: second order kinetics in myelinated nerve

摘要: 1. Kinetics of inactivation sodium channels in myelinated nerve from Rana pipiens were studied at 4·5 °C using the voltage clamp technique Dodge & Frankenhaeuser (1958). 2. Potassium currents blocked by cutting internodes 20 m M-TEA-Cl + 100 M-KCl and adding 12 to external Ringer. Leakage capacitative subtracted electronically. 3. recovery inactivating with a large depolarizing prepulse allowing recover different potentials; extent was measured applying test pulse various times after prepulse. 4. development two methods. The first measure decay current under maintained depolarization. second method peak as function time onset These methods yielded similar results for kinetics development. 5. Contrary expectations Hodgkin—Huxley formalism, course is not strictly exponential. Rather, complete shows an initial delay which depends on potentials. Development fixed potential exhibits least exponentials. 6. steady-state curve h∞(E) asymmetrical fitted better 1/[1+exp (A1E+B1) +exp (A2E+B2)] than (AE+B)]. 7. Most above kinetic observation can be following modification h system formalism: [Formula: see text] 8. In analysis it necessary modify concept separate processes, activation inactivation, governing opening closing channels.