Fig. 1

Experimental setup and data analysis. (a) Experiment setup – a phase contrast image of a patch pipette (on the right) attached to the membrane of an iPSC-derived cortical neuron with the single-cell perfusion tube for extracellular buffer exchange on the left. (b) Example of \(\:I-V\) data for one experiment (\(\:n=1\)) analyzed with Eq. (1): \(\:{V}_{\text{r}\text{e}\text{v}}\) and \(\:{V}_{\text{h}\text{a}\text{l}\text{f}}\) are shown on the Figure, \(\:{G}_{\text{m}\text{a}\text{x}}=0.01\pm\:0.00\) µ S, \(\:z=-0.22\pm\:0.03\). (c) Top: Representative traces with colored currents at selected voltage steps to show signal evolution. Bottom: Stimulating protocol used: consecutive sixteen voltage steps from − 100 mV to + 50 mV with + 10 mV increments. (d) Representative traces of current recordings for one sequence of timeline-ordered perfusions, from left to right: NaCl, ⁶LiCl ⁷LiCl; ^natLiCl; KCl; CsCl; NaCl. For all ionic solutions shown, the time-dependence of the current traces resulting from the consecutive sixteen + 10 mV voltage steps is shown. The dashed line indicates the maximum current achieved during the first NaCl perfusion. (e) Representative current traces for recording in NaCl buffer over 7 minutes to represent rundown in the same buffer. The dashed line indicates the maximum current achieved during the first NaCl perfusion. All examples in this figure are shown for iPSC-derived cortical neurons.