Voltage-activated potassiumchannels of the inhibitory interneurons of hippocampal culture
O.O.Grygorov, A.O.Moskalyuk, S.A.Fedulova, N.S.Veselovsky
O.O. Bogomoletz Institute of Physiology, National Academyof Sciences of Ukraine, Kyiv, Ukraine;International Centre for Molecular Physiology, Kyiv
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Abstract
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 po-
tassium 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 hip-
pocampal 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 sub-
families. The main contribution (83 ± 1.7 % of total ampli-
tude) 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 sub-
family 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.
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