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Medientyp:
E-Artikel
Titel:
Origin Sites of Calcium Release and Calcium Oscillations in Frog Sympathetic Neurons
Beteiligte:
McDonough, Stefan I.;
Cseresnyés, Zoltán;
Schneider, Martin F.
Erschienen:
Society for Neuroscience, 2000
Erschienen in:
The Journal of Neuroscience, 20 (2000) 24, Seite 9059-9070
Sprache:
Englisch
DOI:
10.1523/jneurosci.20-24-09059.2000
ISSN:
0270-6474;
1529-2401
Entstehung:
Anmerkungen:
Beschreibung:
In many neurons, Ca2+signaling depends on efflux of Ca2+from intracellular stores into the cytoplasm via caffeine-sensitive ryanodine receptors (RyRs) of the endoplasmic reticulum. We have used high-speed confocal microscopy to image depolarization- and caffeine-evoked increases in cytoplasmic Ca2+levels in individual cultured frog sympathetic neurons. Although caffeine-evoked Ca2+wave fronts propagated throughout the cell, in most cells the initial Ca2+release was from one or more discrete sites that were several micrometers wide and located at the cell edge, even in Ca2+-free external solution. During cell-wide cytoplasmic [Ca2+] oscillations triggered by continual caffeine application, the initial Ca2+release that began each Ca2+peak was from the same subcellular site or sites. The Ca2+wave fronts propagated with constant amplitude; the spread was mostly via calcium-induced calcium release. Propagation was faster around the cell periphery than radially inward. Local Ca2+levels within the cell body could increase or decrease independently of neighboring regions, suggesting independent action of spatially separate Ca2+stores. Confocal imaging of fluorescent analogs of ryanodine and thapsigargin, and of MitoTracker, showed potential structural correlates to the patterns of Ca2+release and propagation. High densities of RyRs were found in a ring around the cell periphery, mitochondria in a broader ring just inside the RyRs, and sarco-endoplasmic reticulum Ca2+ATPase pumps in hot spots at the cell edge. Discrete sites at the cell edge primed to release Ca2+from intracellular stores might preferentially convert Ca2+influx through a local area of plasma membrane into a cell-wide Ca2+increase.