Rabbah Pascale, Golowasch Jorge, Nadim Farzan
Department of Biological Sciences, Rutgers University, Newark, New Jersey, USA.
J Neurophysiol. 2005 Jul;94(1):519-30. doi: 10.1152/jn.00043.2005. Epub 2005 Feb 23.
Recent studies have found electrical coupling to be more ubiquitous than previously thought, and coupling through gap junctions is known to play a crucial role in neuronal function and network output. In particular, current spread through gap junctions may affect the activation of voltage-dependent conductances as well as chemical synaptic release. Using voltage-clamp recordings of two strongly electrically coupled neurons of the lobster stomatogastric ganglion and conductance-based models of these neurons, we identified effects of electrical coupling on the measurement of leak and voltage-gated outward currents, as well as synaptic potentials. Experimental measurements showed that both leak and voltage-gated outward currents are recruited by gap junctions from neurons coupled to the clamped cell. Nevertheless, in spite of the strong coupling between these neurons, the errors made in estimating voltage-gated conductance parameters were relatively minor (<10%). Thus in many cases isolation of coupled neurons may not be required if a small degree of measurement error of the voltage-gated currents or the synaptic potentials is acceptable. Modeling results show, however, that such errors may be as high as 20% if the gap-junction position is near the recording site or as high as 90% when measuring smaller voltage-gated ionic currents. Paradoxically, improved space clamp increases the errors arising from electrical coupling because voltage control across gap junctions is poor for even the highest realistic coupling conductances. Furthermore, the common procedure of leak subtraction can add an extra error to the conductance measurement, the sign of which depends on the maximal conductance.
最近的研究发现，电耦合比之前认为的更为普遍，并且已知通过缝隙连接的耦合在神经元功能和网络输出中起着关键作用。特别是，通过缝隙连接的电流传播可能会影响电压依赖性电导的激活以及化学突触释放。利用龙虾口胃神经节中两个强电耦合神经元的电压钳记录以及这些神经元的基于电导的模型，我们确定了电耦合对泄漏电流和电压门控外向电流测量以及突触电位的影响。实验测量表明，泄漏电流和电压门控外向电流均由与钳制细胞耦合的神经元通过缝隙连接募集。然而，尽管这些神经元之间存在强耦合，但在估计电压门控电导参数时产生的误差相对较小（<10%）。因此，在许多情况下，如果电压门控电流或突触电位的测量误差在可接受范围内，则可能不需要分离耦合神经元。然而，建模结果表明，如果缝隙连接位置靠近记录位点，此类误差可能高达20%；而在测量较小的电压门控离子电流时，误差可能高达90%。矛盾的是，改进的空间钳制会增加由电耦合引起的误差，因为即使对于最高的实际耦合电导，缝隙连接上的电压控制也很差。此外，常见的泄漏电流减法程序会给电导测量增加额外的误差，其符号取决于最大电导。
