Fig. 7
From: The retinal pigment epithelium displays electrical excitability and lateral signal spreading
Stochasticity of spike onset. A Spikes can occur apparently spontaneously when the cell is hyperpolarized by current injection; asterisks denote two particularly sharp depolarizing transients and the double asterisk the region of spontaneous hyperpolarization preceding the actual spike (arrow). B Magnified spike-containing segment from (A). C I–V and SSI relations for another cell characterized by a large INa with a comparatively negative INa activation threshold. D Parts of three voltage traces from a current-clamp recording, with a spike at 360 ms on the black trace. E Variability in spike properties in the INa activation threshold region. F Distribution of minimal resting potentials, its Gaussian fit, and the INa availability curve obtained by fitting the SSI data from Fig. 2D; the Vrest histogram data were divided by the maximum value. G, H Ionic currents (G) evoked from a holding potential of −70 mV in an RPE cell with a very negative Vrest and the associated current-clamp recording (H)