A novel voltage-dependent cation current in rat neocortical neurones.
1. Using the whole-cell configuration of the patch-clamp technique, an unexpected voltage-dependent cation current (Icat) was recorded from acutely isolated rat neocortical neurones, the Na+, K+ and Ca2+ currents of which were pharmacologically suppressed. 2. Icat was activated at potentials more positive than -45 mV, displayed outward rectification, and deactivated with a slow voltage-dependent time course causing prominent inward tail currents. 3. Activation of Icat was not dependent on Ca2+ influx or increases in cytosolic Ca2+, since it was not abolished by inorganic Ca2+ channel blockers or by internal Ca2+ chelators. 4. Icat was reduced by tetraethylammonium at high concentrations, but not by 4-amino-pyridine, and proved to be insensitive to cation channel blockers such as Cs+, amiloride or gadolinium. 5. Ion substitution experiments revealed that the channel producing Icat was permeable to a number of monovalent cations, including K+, Cs+, Na+ and choline+, but not to the Cl-anion. 6. The features of Icat suggest that, in electrically active neurones, it should play a role in both the initial repolarization of membrane potential after strong depolarization and the generation of depolarizing after-potential.
Alzheimer
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Department of Physiology, University of Munich, Germany.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002412:Cations / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002463:Cell Membrane Permeability; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008564:Membrane Potentials; D009044:Motor Cortex / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D002412:Cations; D007473:Ion Channels; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D002118:Calcium