Poor voltage clamp quality in astrocyte recording. (a) DIC and SR101 fluorescent images of a dual patch recorded astrocyte in the hippocampal CA1 stratum radiatum region; electrode 1 (E1) and electrode 2 (E2) were in voltage clamp and current clamp modes, respectively. (b) Whole-cell current profiles of an astrocyte and an NG2 glia are shown as indicated; the cells were held at resting (-80 mV), then stepped to command voltages from -180 mV to +20 mV with 20 mV increments (inset). (c, d) Comparison of command voltages (VC) applied through E1 and the resultant potentials across the membrane (VM) measured from E2 for the recorded astrocyte and NG2 glia, respectively. (e, f) The I-VC and I-VM were plotted in the same chart for voltage clamp quality comparison. (g) The Rt was plotted against VM/ΔVC (n = 44) and fitted with ΔVM/ΔVC = aRtb; the VM/ΔVC decreases with increasing Rt, which yields RM and exponent values of 5.73 MΩ and -0.995, respectively. (h) Comparison of I-VM relationships in the presence and absence of Ra compensation, showing a good voltage clamp quality after Ra compensation.