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. 2019 Jul 5;118(4):813–825. doi: 10.1016/j.bpj.2019.06.033

Figure 6.

Figure 6

Residuals measured from HEK293 cells stably expressing SERT cells challenged with cocaine or 5-HT can be decomposed into a battery and a capacitive residual. (A) The upper panel shows a residual obtained from recordings of a HEK293 cell stably expressing SERT, which was superfused with cocaine binding (gray trace). The measured residual was fitted to the simple circuit shown in the lower panel. The inset shows the magnified rising phase of the residual. The fit (in green) did not adequately account for the initial phase of the residual. The lower panel depicts the simple model. (B) The upper panel shows the same residual as in (A) fitted to the analytical solution of a more complex circuit displayed in the lower panel of (B). The fit (in orange) allowed for decomposing the measured residual into a battery (in red) and a capacitive residual (in blue). The lower panel depicts the complex model (C). Shown is a comparison of the fitted residuals of the simple model (in green) and the complex model (in orange). The inset shows the magnified initial phase of the fit. In the initial phase, the more complex model better accounted for the data. (D) Shown is the contribution of the battery component in percentage to the total change in CM induced by cocaine. Shown is the summery of six independent experiments. In average, the contribution of the battery component was 60 ± 20%. (E) Change in ΔΔVS over time as a result of cocaine binding is plotted along with the simultaneous change in CM. (F) Shown is the measured residual of a HEK293 cell stably expressing SERT, which was challenged with 30 μM serotonin (5-HT) in the absence of extracellular Cl− (in gray). The residual was fitted to the complex model. The fit (orange trace) decomposed the measured residual into a battery (in red) and a capacitive residual (in blue). (G) Shown is a summary of four independent experiments in which 5-HT was applied. Plotted in percentage is the contribution of the battery residual to the total change in capacitance (67.0 ± 11.9%). To see this figure in color, go online.