Yelhekar Tushar D, Druzin Michael, Karlsson Urban, Blomqvist Erii, Johansson Staffan
Section for Physiology, Department of Integrative Medical Biology, Umeå University Umeå, Sweden.
Front Cell Neurosci. 2016 Feb 2;10:10. doi: 10.3389/fncel.2016.00010. eCollection 2016.
The relation between current and voltage, I-V relation, is central to functional analysis of membrane ion channels. A commonly used method, since the introduction of the voltage-clamp technique, to establish the I-V relation depends on the interpolation of current amplitudes recorded at different steady voltages. By a theoretical computational approach as well as by experimental recordings from GABAA-receptor mediated currents in mammalian central neurons, we here show that this interpolation method may give reversal potentials and conductances that do not reflect the properties of the channels studied under conditions when ion flux may give rise to concentration changes. Therefore, changes in ion concentrations may remain undetected and conclusions on changes in conductance, such as during desensitization, may be mistaken. In contrast, an alternative experimental approach, using rapid voltage ramps, enable I-V relations that much better reflect the properties of the studied ion channels.
电流与电压的关系，即I-V关系，是膜离子通道功能分析的核心。自电压钳技术问世以来，一种常用的建立I-V关系的方法依赖于对在不同稳定电压下记录的电流幅度进行插值。通过理论计算方法以及对哺乳动物中枢神经元中GABAA受体介导电流的实验记录，我们在此表明，这种插值方法可能给出的反转电位和电导率并不能反映在离子通量可能导致浓度变化的条件下所研究通道的特性。因此，离子浓度的变化可能未被检测到，并且关于电导率变化（例如在脱敏过程中）的结论可能是错误的。相比之下，另一种使用快速电压斜坡的实验方法能够得到能更好反映所研究离子通道特性的I-V关系。
