Voltage-dependent sodium and potassium currents in cultured trout astrocytes.

TY - JOUR

T1 - Voltage-dependent sodium and potassium currents in cultured trout astrocytes.

AU - Glassmeier, Günter

AU - Jeserich, G

AU - Krüppel, T

PY - 1994

Y1 - 1994

N2 - Voltage-gated ionic currents were recorded from cultured trout astrocytes with the whole-cell variation of the patch-clamp technique. In a subpopulation of astrocytes depolarizations above -40 mV activated a fast transient inward current that was identified as a sodium current by ion substitution experiments, its current reversal potential, and its TTX-sensitivity. Regarding threshold of activation, peak current voltage, and amplitude this current closely resembled those previously described for mammalian astrocytes. Voltage-dependence of inactivation and kinetics, however, markedly differed from the "glial-like" sodium current occurring in mammalian hippocampal or optic nerve astrocytes, since the sodium current of trout astrocytes exhibited a faster time course of activation and decay and a more depolarized steady-state inactivation curve with midpoints close to -60 mV. During a period of 2 weeks in culture the biophysical properties of the sodium current did not change significantly, albeit a continuous decrease in current density was observed. At depolarizing voltage steps positive to -40 mV, additionally voltage-gated potassium outward currents were evoked, which could be separated into a steady-state current with delayed rectifier properties and an inactivating component resembling the A-type current. Moreover, in a subpopulation of astrocytes an inward potassium current was elicited at hyperpolarizing potentials, which exhibited biophysical features consistent with the potassium inward rectifier of mammalian astrocytes.

AB - Voltage-gated ionic currents were recorded from cultured trout astrocytes with the whole-cell variation of the patch-clamp technique. In a subpopulation of astrocytes depolarizations above -40 mV activated a fast transient inward current that was identified as a sodium current by ion substitution experiments, its current reversal potential, and its TTX-sensitivity. Regarding threshold of activation, peak current voltage, and amplitude this current closely resembled those previously described for mammalian astrocytes. Voltage-dependence of inactivation and kinetics, however, markedly differed from the "glial-like" sodium current occurring in mammalian hippocampal or optic nerve astrocytes, since the sodium current of trout astrocytes exhibited a faster time course of activation and decay and a more depolarized steady-state inactivation curve with midpoints close to -60 mV. During a period of 2 weeks in culture the biophysical properties of the sodium current did not change significantly, albeit a continuous decrease in current density was observed. At depolarizing voltage steps positive to -40 mV, additionally voltage-gated potassium outward currents were evoked, which could be separated into a steady-state current with delayed rectifier properties and an inactivating component resembling the A-type current. Moreover, in a subpopulation of astrocytes an inward potassium current was elicited at hyperpolarizing potentials, which exhibited biophysical features consistent with the potassium inward rectifier of mammalian astrocytes.

M3 - SCORING: Zeitschriftenaufsatz

VL - 11

SP - 245

EP - 254

JO - GLIA

JF - GLIA

SN - 0894-1491

IS - 3

M1 - 3

ER -