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Calcium current activated by potassium ions in voltage‐clamped rat hippocampal pyramidal neurones
Author(s) -
Deák Ferenc,
Nagy Gábor,
Várnai Péter,
Madarász Emília,
Spät András
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.735bp.x
Subject(s) - chemistry , patch clamp , extracellular , hippocampal formation , biophysics , hyperpolarization (physics) , membrane potential , reversal potential , inward rectifier potassium ion channel , calcium , potassium channel , ion channel , neuroscience , biochemistry , biology , stereochemistry , organic chemistry , receptor , nuclear magnetic resonance spectroscopy
1 Neuronal activity results in local elevation of extracellular K + concentration ([K + ] o ). 2 Using the patch‐clamp technique in the whole‐cell configuration, we investigated whether extracellular K + activates non‐voltage‐operated Ca 2+ channels in pyramidal cells cultured from rat embryonic hippocampi. 3 K + (12 mM) reversibly activated a sustained inward current at a holding potential of ‐100 mV. Membrane conductance and variance of noise were significantly increased by K + . This current could be observed at membrane potentials negative to +60 mV. 4 Inhibitors of inward rectifier K + channels and hyperpolarization‐induced cation current reduced the current only at potentials negative to ‐50 mV. 5 The K + ‐induced current was activated in Na + ‐free but not in Ca 2+ ‐free medium, did not depend on cytosolic [Cl − ], and was blocked by Cd 2+ but not by organic channel inhibitors. 6 Half‐maximal activation of the current (at ‐100 mV) was attained at [K + ] o ≈ 20 mM. 7 The current is similar to I gl , a K + ‐induced Ca 2+ current described in glomerulosa cells. It was also present in pyramidal cells from prefrontal cortex but not in hippocampal bipolar and glial cells. 8 Activation of K + ‐induced Ca 2+ current may elevate cytoplasmic [Ca 2+ ] at [K + ] o levels which are insufficent to activate voltage‐dependent Ca 2+ channels.