FIGURE 3.

Analysis of syncytial isopotentiality. (A) In a single freshly dissociated astrocyte, the K⁺ free/Na⁺ containing electrode solution ([Na⁺]_p) progressively substituted the endogenous K⁺ content in whole-cell recording, leading to a V_M depolarization toward 0 mV as predicated by Nernstian equation. (B) The V_M recorded from an astrocyte in situ with the [Na⁺]_p disobeys the Nernstian prediction. Instead, the steady-state V_M (V_M,SS) maintained at a quasi-physiological level as a result of voltage compensation by the physiological V_M of the coupled neighbors. (C) The relationship between V_M,SS and coupling strength (S) predicted by computational modeling. (D) According to this modeling shown in (C), the V_M,SS can be shifted toward a more hyperpolarizing V_M of neighboring astrocytes due to a stronger syncytial coupling (S) or due to a weaker coupling strength (S), the V_M,SS toward the GHK predication for the V_M of [Na⁺]_p at 0 mV. V_M,I stands for initial V_M recorded immediately after break-in of cell membrane, reflecting the resting V_M of the recorded astrocyte. Figure modified from Kiyoshi et al. (2018).