Analysis of sodium channel tail currents.

Publisher Summary This chapter focuses on whole-cell patch clamp experiments in clonal pituitary GH 3 cells and illustrates how the analysis of tail currents has helped to explore the properties of Na + channels, including the kinetics of channel inactivation and the interaction of divalent and trivalent cations with the channels. Divalent and trivalent cations have strong effects on Na + channel function. They shift the gating behavior of the channel along the voltage axis and Ca 2+ causes voltage-dependent block of the channels. The chapter proposes that both actions—blocking and shifting—are related to Ca 2+ entry into the Na + channels. This proposal is based on the finding of a close correlation between Ca 2+ block and the effects of Ca 2+ on gating. Ca 2+ entry into Na + channels, thus, seems to play a part in the opening and dosing of these channels; this suggests that the channel activation gates close stably, when the channel is occupied by Ca 2+ .