Calcium stores in hippocampal synaptic boutons mediate short-term plasticity, store-operated Ca2+ entry, and spontaneous transmitter release.
Evoked transmitter release depends upon calcium influx into synaptic boutons, but mechanisms regulating bouton calcium levels and spontaneous transmitter release are obscure. To understand these processes better, we monitored calcium transients in axons and presynaptic terminals of pyramidal neurons in hippocampal slice cultures. Action potentials reliably evoke calcium transients in axons and boutons. Calcium-induced calcium release (CICR) from internal stores contributes to the transients in boutons and to paired-pulse facilitation of EPSPs. Store depletion activates store-operated calcium channels, influencing the frequency of spontaneous transmitter release. Boutons display spontaneous Ca2+ transients; blocking CICR reduces the frequency of these transients and of spontaneous miniature synaptic events. Thus, spontaneous transmitter release is largely calcium mediated, driven by Ca2+ release from internal stores. Bouton store release is important for short-term synaptic plasticity and may also contribute to long-term plasticity.
Emptage
N J
NJ
Division of Neurophysiology, National Institute for Medical Research, NW7 1AA, London, United Kingdom.
Reid
C A
CA
Fine
A
A
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001369:Axons / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008239:Lysine / Q000031:analogs & derivatives; D008297:Male; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012433:Ryanodine / Q000494:pharmacology; D016708:Synaptophysin / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
D015220:Calcium Channels; D018377:Neurotransmitter Agents; D016708:Synaptophysin; D012433:Ryanodine; D013779:Tetrodotoxin; C013411:biocytin; D008239:Lysine; D002118:Calcium