An IP3-assisted form of Ca2+-induced Ca2+ release in neocortical neurons.
Calcium increases induced by single action potentials in rat visual cortex layer II/III pyramidal neurons were shown to be augmented by muscarinic acetylcholine receptor (mAchR) stimulation. This augmentation was drastically reduced by intracellular injection of heparin but not ruthenium red, therefore involving inositol-1,4,5-trisphosphate (IP3)-sensitive rather than ryanodine-sensitive calcium stores. Only the calcium increase induced by the second or later spike of a spike train, but not that induced by the first spike, was augmented, indicating the requirement of both spike-induced calcium increase and mAchR activation. The calcium store depletor thapsigargin abolished this augmentation use-dependently. These findings suggest a neocortical occurrence of calcium-induced calcium release from IP3-sensitive calcium stores that have been sensitized beforehand by IP3 through mAchR-mediated mechanisms.
Yamamoto
K
K
Department of Integrative Brain Science, Kyoto University Graduate School of Medicine, Japan.
Hashimoto
K
K
Isomura
Y
Y
Shimohama
S
S
Kato
N
N
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018721:Muscarinic Agonists / Q000494:pharmacology; D019579:Neocortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects; D012430:Ruthenium Red / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018721:Muscarinic Agonists; D018160:Receptors, Cytoplasmic and Nuclear; D012430:Ruthenium Red; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D006493:Heparin; D002118:Calcium