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Role of extracellular Ca 2+ in gating of Ca V 1.2 channels
Author(s) -
Babich Olga,
Isaev Dmytro,
Shirokov Roman
Publication year - 2005
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 - 10.1113/jphysiol.2005.086561
Subject(s) - extracellular , gating , chemistry , conductance , biophysics , reversal potential , calcium , ionic bonding , patch clamp , ion , biochemistry , biology , receptor , physics , condensed matter physics , organic chemistry
We examined changes in ionic and gating currents in Ca V 1.2 channels when extracellular Ca 2+ was reduced from 10 m m to 0.1 μ m . Saturating gating currents decreased by two‐thirds ( K D ≈ 40 μ m ) and ionic currents increased 5‐fold ( K D ≈ 0.5 μ m ) 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.