Fast inactivating potassium current in cultured hippocampal neurons |
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Authors: | S A Fedulova |
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Institution: | (1) International Center for Molecular Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine |
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Abstract: | Using a voltage-clamp whole-cell technique, we studied transmembrane currents in hippocampal neurons after their long-lasting
cultivation. Based on the activational characteristics and data on pharmacological sensitivity, we isolated and described
an A-type voltage-activated fast inactivating potassium current (FIPC). This transient FIPC was activated at −50… −40 mV and
was rather sensitive to 4-aminopyridine (4-AP). Extracellular application of 5 mM 4-AP decreased the FIPC amplitude by 75%,
while application of 10 mM tetraethylammonium evoked no significant changes in it. Kinetics of FIPC activation could be described
by one exponent in the fourth degree. With variations of the membrane potential from −40 to 30 mV, the activation time constant
varied from 2.8 to 1.5 msec. Inactivation kinetics was described by one exponent with the time constant varying from 37 msec
at −45 mV to 18 msec at 40 mV. Stationary activation and inactivation curves could be described by Boltzmann's equation; a
half value of the level of stationary inactivation was reached at −80 mV, while stationary activation was attained at −25
mV. Kinetics of deinactivation (from stationary inactivation) was monoexponential with the time constant of 41 msec. It is
supposed that FIPC through the membrane of hippocampal neurons is provided by the type Kv4.2 potassium channels. |
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