Tracking presynaptic Ca2+ dynamics during neurotransmitter release with Ca2+-activated K+ channels.
Neurotransmitter release during action potentials is thought to require transient, localized [Ca2+]i as high as hundreds of micromolar near presynaptic release sites. Most experimental attempts to characterize the magnitude and time course of these Ca2+ domains involve optical methods that sample large volumes, require washout of endogenous buffers and often affect Ca2+ kinetics and transmitter release. Endogenous calcium-activated potassium (KCa) channels colocalize with presynaptic Ca2+ channels in Xenopus nerve-muscle cultures. We used these channels to quantify the rapid, dynamic changes in [Ca2+]i at active zones during synaptic activity. Confirming Ca2+-domain predictions, these KCa channels revealed [Ca2+]i over 100 microM during synaptic activity and much faster buildup and decay of Ca2+ domains than shown using other techniques.
Yazejian
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Department of Physiology and Jerry Lewis Neuromuscular Research Center, UCLA School of Medicine, Los Angeles, California 90095, USA.
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Grinnell
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D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D051036:Large-Conductance Calcium-Activated Potassium Channels; D009132:Muscles / Q000166:cytology; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D017729:Presynaptic Terminals / Q000378:metabolism*; D011930:Reaction Time / Q000502:physiology; D014981:Xenopus; D020866:omega-Conotoxin GVIA / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D018377:Neurotransmitter Agents; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; C064719:iberiotoxin; D020866:omega-Conotoxin GVIA; D002118:Calcium