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Updated: Aug 18, 2026

Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels
Published on: December 13, 2024
Role of extracellular Ca2+ in gating of CaV1.2 channels
Olga Babich1, Dmytro Isaev, Roman Shirokov
1Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103, USA.
Abstract:
We examined changes in ionic and gating currents in Ca(V)1.2 channels when extracellular Ca(2+) was reduced from 10 mm to 0.1 microm. Saturating gating currents decreased by two-thirds (K(D) approximately 40 microm) and ionic currents increased 5-fold (K(D) approximately 0.5 microm) due to increasing Na(+) conductance. A biphasic time dependence for the activation of ionic currents was observed at low [Ca(2+)], which appeared to reflect the rapid activation of channels that were not blocked by Ca(2+) and a slower reversal of Ca(2+) blockade of the remaining channels. Removal of Ca(2+) following inactivation of Ca(2+) currents showed that Na(+) currents were not affected by Ca(2+)-dependent inactivation. Ca(2+)-dependent inactivation also induced a negative shift of the reversal potential for ionic currents suggesting that inactivation alters channel selectivity. Our findings suggest that activation of Ca(2+) conductance and Ca(2+)-dependent inactivation depend on extracellular Ca(2+) and are linked to changes in selectivity.
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