Activity-dependent calcium sequestration in dendrites of hippocampal neurons in brain slices.
Synaptic activity-dependent changes in the spatio-temporal distribution of calcium ions regulate important neuronal functions such as dendritic integration and synaptic plasticity, but the processes that terminate the free Ca2+ transients associated with these changes remain unclear. We have characterized at the electron microscopic level the intracellular compartments involved in buffering free Ca2+ transients in dendritic cytoplasm of CA3 neurons by measuring the larger changes in the concentrations of total Ca that persist for several minutes after neuronal activity. Quantitative energy-dispersive x-ray microanalysis of cryosections from hippocampal slice cultures rapidly frozen 3 min after afferent synaptic activity identified a subset of dendritic endoplasmic reticulum (ER) as a high-capacity Ca2+ buffer. Calcium sequestration by cisterns of this subset of ER was graded, reversible, and dependent on a thapsigargin-sensitive Ca2+-ATPase. Sequestration was so robust that after repetitive high-frequency stimulation the Ca content of responsive ER cisterns increased as much as 20-fold. These results demonstrate that a subpopulation of ER is the major dendritic Ca sequestration compartment in the minutes after neuronal activity.
Pozzo-Miller
L D
LD
Laboratory of Neurobiology, National Institute of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
Pivovarova
N B
NB
Leapman
R D
RD
Buchanan
R A
RA
Reese
T S
TS
Andrews
S B
SB
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology; D003712:Dendrites / Q000201:enzymology* / Q000648:ultrastructure; D004577:Electron Probe Microanalysis; D004721:Endoplasmic Reticulum / Q000378:metabolism; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005456:Fluorescent Dyes; D006624:Hippocampus / Q000166:cytology* / Q000378:metabolism; D009474:Neurons / Q000201:enzymology / Q000648:ultrastructure; D009924:Organ Culture Techniques; D051381:Rats; D013569:Synapses / Q000737:chemistry / Q000502:physiology
D005456:Fluorescent Dyes; D000252:Calcium-Transporting ATPases; D002118:Calcium