Figure 5. pH-gating of R348H channels expressed in astrocyte-like cells.

Sample current traces for WT (a) and R348H (b) channel expressed in U251 cells, and recorded in the whole-cell configuration by applying voltage ramps from −140 to +30 mV (holding potential of −80 mV), immediately after the establishment of the whole-cell configuration (pHi7.2), after 10 min (pHi6.1), and following external BaCl₂ application (pHi6.1 + 100 μM Ba²⁺). Both cells were recorded using an intracellular pipette solution having a pH of 6.1. (c,d) Representative time courses of WT (c) and R348H (d) currents recorded at −100 mV (normalized to the current recorded immediately after the establishment of the whole-cell configuration), using a pipette solution with pH of either 7.2 (black circles) or 6.1 (grey circles). (e) Plot of the mean fractional WT and R348H current inhibition by an intracellular pH of either 7.2 or 6.1. The fractional current reduction was estimated at −100 mV and calculated as 1− (I_{10 min}/I_{0 min}), in experiments similar to those shown in panels a–d. (f) Plot of the mean WT and R348H current density at −100 mV of applied potential.