Excessive repolarization-dependent calcium currents induced by strong depolarizations in rat skeletal myoballs

The Journal of Physiology
A Fleig, R Penner

Abstract

1. Whole-cell patch-clamp recordings were used to study voltage-dependent Ca2+ currents in skeletal myoballs cultured from newborn rats. 2. Depolarizing voltage pulses evoked classical L-type Ca2+ currents, whereas repolarization induced tail currents, whose properties deviated from the expected behaviour of the preceding Ca2+ currents in both voltage dependence and kinetics. 3. Depolarizations of up to +10 mV primarily recruited tail currents that correspond to the Ca2+ channels activated and conducting during the depolarizing pulse, but stronger depolarizations yielded an additional tail current component that exceeded the 'normal' tail current amplitude by several-fold. 4. Activation kinetics of the tail currents were biexponential, with a fast time constant matching the activation time course of the pulse currents (tau approximately 40 ms) and an additional slower component with a voltage-dependent time course that had no kinetic counterpart in the pulse currents (tau approximately 150-600 ms). 5. Both pulse and tail currents were blocked by the dihydropyridine, PN200-110, suggesting that they represent Ca2+ channels of the L-type. 6. We suggest the presence of at least two subsets of dihydropyridine-sensitive Ca2+ channels...Continue Reading

Citations

Sep 3, 2013·Cell Calcium·Roman V Frolov, Satpal Singh
Sep 25, 1999·The Journal of General Physiology·S Gera, L Byerly
Aug 4, 1998·Current Opinion in Neurobiology·P C GrayW A Catterall
Mar 29, 2005·Proceedings of the National Academy of Sciences of the United States of America·Joanne T HulmeWilliam A Catterall
Sep 17, 1998·The Journal of Biological Chemistry·C MathesR Penner
Feb 21, 1998·Journal of Neurophysiology·P J Kammermeier, S W Jones

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