Fig. 4

Complex expression of rectifying K⁺ conductances in neonatal astrocytes. a To maximally induce outward IK_a, and potential inward INa, a −110 mV/300 ms prepulse was followed by a series of 50 ms steps from −180 to +40 mV with 10 mV increments. Absence of any depolarization-induced inward INa was shown in the inset below (a) after symmetric subtraction of leak and capacitive currents. b To eliminate IK_a, a prepulse at −40 mV/300 ms was followed by test steps from −180 to +40 mV with 10 mV increments and 50 ms duration. c, d The isolated IK_a and its corresponding I-V plot with a V _rev at −40 mV. The IK_a was isolated by off-line subtraction of recording (a and b). e, f Isolated IK_d and its corresponding I-V plot. The IK_d was isolated by symmetric leak and capacitive current subtraction from recording (b). g Inward K⁺ conductance (IK_in) in a P1 astrocyte induced after inhibition of gap junction coupling by incubation of slice with 100 μM MFA. For IK_in activation, a 500 ms pre-pulse at 0 mV was followed by a set of steps from −180 to 0 mV, 50 ms duration and 10 mV increments. h Addition of 100 μM Ba²⁺ for 15 min substantially reduced the initial IK_in. i Subtracted Ba²⁺-sensitive currents. j I-V plots illustrate the total IK_in, Ba²⁺-sensitive IK_in and the remaining outward Ba²⁺-insensitive currents as indicated by color codes. The Ba²⁺ -sensitive and insensitive conductances were reversed at −79.7 mV and 79.7 mV, respectively