Fig. 7

Neonatal astrocytes exhibit a deficient K⁺ uptake capacity. a, b The V _M responses from a neonatal and mature astrocyte as indicated. To test K⁺ uptake capacity, the K⁺ ions in the electrode were replaced fully by Na⁺ ions, whereas the bath K⁺ remained at the physiological 3.5 mM. A negative holding current (I _holding) was applied at incremental duration from 1 to 5 s to shift the V _M downward to −75 mV. In between the I _holding pulses, the cell was maintained at I _holding = 0 for V _M recovery back to the resting levels. The longer the duration of the I _holding pulses, the larger the induced maximal V _M hyperpolarization. Also, the longer the duration of I _holding pulse, the more negative of the V _rev s, indicating more accumulation of K⁺ inside astrocytes (see c and d in expanded scale). The V _rev deviated much less from the resting V _M in neonatal astrocytes compared to mature astrocytes. e According to GHK equation, the estimated intracellular K⁺ concentrations, corresponding to the V _rev values, are plotted against the I _holding pulse durations for neonatal and mature astrocytes as indicated by color codes. Overall, the capacity of K⁺ uptake in neonatal astrocytes is ~50 % less than mature astrocytes