Voltage-dependent calcium channels in cultivated neurons of the rat hippocampus |
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Authors: | E V Isaeva S A Fedulova N S Veselovskii |
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Institution: | (1) Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine |
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Abstract: | Calcium currents through the somatic membrane of cultivated (a low-density culture) hippocampal neurons of rats were studied
with the use of a patch-clamp technique in the whole-cell configuration. Low- and high-threshold components of calcium currents
were found in the somata of all studied cells. Low-threshold currents were activated at a membrane potential of about−75 mV
and reached the maximum amplitude at −45±4 mV, while the maximum amplitude of high-threshold currents was observed at 17±6
mV. Low-threshold calcium currents differed from high-threshold current in weak suppression by low Cd2+ concentration (10–20 μM), while Ni2+ inhibited both types of calcium currents to an equal extent. Experiments with organic channel blockers showed that in most
neurons at least four channel types were expressed: these were L, N, P, and channels insensitive to the used blockers (presumably,
R-type). A blocker of L-type calcium channels, nifedipine (10 μM), blocked, on the average, 22.7±5.2%; a blocker of N-type
channels, ω-CTx-GVIA (1.0 μM), blocked 30.0±5.0% and a blocker of P/Q channels, ω-Aga-IVA (200 nM), blocked 37.2±13.3% of
the integral high-threshold current. A resistive component equalled 15.7±5.1% of the latter current. It is concluded that
hippocampal neurons cultivated with a low density express a pharmacologically heterogeneous population of calcium channels,
and the relative proportions of different type channels are close to the earlier described channel type composition in rat
hippocampal slices. Our study shows that the low-density culture can be used as an adequate model for studying calcium channels
in the somatic membrane of hippocampal neurons. |
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