Characterizing Human Ion Channels in Induced Pluripotent Stem Cell-Derived Neurons

Neurons derived from human-induced pluripotent stem cells were characterized using manual and automated patch-clamp recordings. These cells expressed voltage-gated Na+ (Na-v), Ca2+ (Ca-v), and K+ (K-v) channels as expected from excitable cells. The Na-v current was TTX sensitive, IC50 = 12 +/- 6 nM (n = 5). About 50% of the Ca-v current was blocked by 10 mu M of the L-type channel blocker nifedipine. Two populations of the K-v channel were present in different proportions: an inactivating (A-type) and a noninactivating type. The A-type current was sensitive to 4-AP and TEA (IC50 = 163 +/- 93 mu M; n = 3). Application of gamma-aminobutyric acid (GABA) activated a current sensitive to the GABA(A) receptor antagonist bicuculline, IC50 = 632 +/- 149 nM (n = 5). In both devices, comparable action potentials were generated in the current clamp. With unbiased, automated patch clamp, about 40% of the cells expressed Na-v currents, whereas visual guidance in manual patch clamp provided almost a 100% success rate of patching excitable cells. These results show high potential for pluripotent stem cell-derived neurons as a useful model for drug discovery, in combination with automated patch-clamp recordings for high-throughput and high-quality drug assessments at human neuronal ion channels in their correct cellular background.