[Voltage-activated potassium channels of the inhibitory interneurons of the hippocampus in culture].

Potassium channels make up the largest family of voltage-activated channels and play a key role in maintenance of cell excitability and in transmission of information within the nervous system. The aim of this work was to find out the specific subtypes of voltage-activated potassium channels peculiar to GABAergic interneurons of rat hippocampal culture. It was shown that total depolarization-evoked outward potassium current in any interneuron studied had the activation threshold about -50 mV. The specific Kv1 channels' blocker a-DTX influenced neither amplitude nor kinetics of total current, thus we excluded the participation of these channels in its forming. The transient A-current made up 9.4+/-1.3% of the amplitude of total current and had low sensitivity to 4-AP that was an evidence of the presence of Kv4 channels in hippocampal interneurons. The slow inactivating component of integral potassium current was relatively small and had the time constant of inactivation 3 +/- 0.15 s that is typical for delayed rectifier potassium channels of Kv2 and Kv3 subfamilies. The main contribution (83 +/- 1.7 % of total amplitude) to the integral current belonged to the non-inactivating current. Prolonged depolarization of any interneuron tested to -20 mV evoked a steady non-inactivating outward current with amplitude 100-400 pA and activation threshold about -60 mV. Retigabine shifted its I-V plot to more negative values and increased the amplitude at -20 mV by 66+/-14%. These facts can be evidence of the participation of KCNQ channels subfamily in the forming of non-inactivating current. But selective blockers of KCNQ channels linopirdine and XE991 had very small influence on steady-state outward current that means the current appears owing to activity of linopirdine-insensitive forms of KCNQ channels or channels of a different, unknown family.