An electrophysiological and kinematic model of Paramecium, the “swimming neuron”
Fig 5
Passive properties and inward rectifier current.
A, Top: voltage responses of one cell to negative current pulses (I = 0 to -4 nA in 300 pA increments; dashed lines: start and end of pulses), in the standard extracellular solution (4 mM KCl and 1 mM CaCl2). The arrow points at an inflexion due to the inward rectifier current IKir. Bottom: model responses fitted to the data, showing the inferred reversal potential of K+ (EK) and the half-activation voltage VKir of the inward rectifier current. B, Current-voltage relationship over all cells (mean ± standard deviation, measured at pulse end) in 4 mM KCl (grey) and 0 mM KCl (blue). Removing K+ from the extracellular solution largely suppresses the inward current. C, Activation curve of the inward rectifier current in the fitted models. The current activates below EK (EL is leak reversal potential). The solid curve is the activation function with median parameters, the dashed curve is the activation function of the cell shown in A. D, Fitted parameters over n = 28 cells, grouped in passive parameters and inward rectifier parameters.