Synaptically activated increases in Ca2+ concentration in hippocampal CA1 pyramidal cells are primarily due to voltage-gated Ca2+ channels.
Changes in intracellular Ca2+ concentration ([Ca2+]i) in the soma and dendrites of hippocampal CA1 pyramidal neurons were measured using intracellularly injected fura-2. A large component of the [Ca2+]i elevation caused by high frequency stimulation of the Schaffer collaterals was correlated with the Na+ spikes triggered by the excitatory postsynaptic potentials (EPSPs). These spikes were generated in the soma and proximal dendrites and stimulated Ca2+ entry through voltage-gated Ca2+ channels. Suppressing spikes by hyperpolarizing the soma or by injecting QX-314 revealed a smaller nonspike component of Ca2+ entry. A substantial fraction of this component was mediated by the action of the EPSPs on voltage-gated Ca2+ channels, because it persisted in 2-amino-5-phosphonovaleric acid and because it was usually reduced when Ca2+ channel activity was suppressed by hyperpolarization. Ca2+ entry through the N-methyl-D-aspartate receptor channel could not be detected with certainty, perhaps because it was highly localized.
Department of Physiology, Yamagata University School of Medicine, Japan.
H
H
Miyakawa
W N
WN
Ross
D
D
Jaffe
J C
JC
Callaway
N
N
Lasser-Ross
J E
JE
Lisman
D
D
Johnston
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D003712:Dendrites / Q000502:physiology; D004558:Electric Stimulation; D005071:Evoked Potentials; D016257:Fura-2; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007700:Kinetics; D008012:Lidocaine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013050:Spectrometry, Fluorescence; D013569:Synapses / Q000187:drug effects / Q000502:physiology*
D000779:Anesthetics, Local; D015220:Calcium Channels; C012647:QX-314; D015763:2-Amino-5-phosphonovalerate; D008012:Lidocaine; D002118:Calcium; D016257:Fura-2