Functional characterization of differentiated astrocytes.

(A) Representative traces of ionic currents evoked by ramp protocol (left) and voltage-step protocol (right) in cultured WT, HD, and shHD astrocytes. The holding potentials for all the cells were -60mV. (B) Plots of resting membrane potential values for the three types of cells recorded before the current membrane activation. There is no statistical significance among three groups. (C) Percentage of ramp current decrease measured at +100 mV by application of 4-AP (500 uM) in the superfusion medium during recordings on all three types of astrocytes. (D) Significant decreases in the amplitude of peak ramp currents were observed in WT astrocytes following 20 min application of TBOA at the concentration of 500 uM (n = 6). (E, F, G) I/V plots show that all three types of astrocytes share the similarity with variably rectifying astrocyte reported in the literature. However, the reversal potential of (F) HD astrocytes was significantly shifted compared with those in both (E) WT and (G) shHD cells. At least four biological replicates were included for each cell line, and n represents each individual reading.