The entry and clearance of Ca super(2+) at individual presynaptic active zones of hair cells from the bullfrog's sacculus

Neurotransmitter is released when Ca super(2+) triggers the fusion of synaptic vesicles with the plasmalemma. To study factors that regulate Ca super(2+) concentration at the presynaptic active zones of hair cells, we used laser-scanning confocal microscopy with the fluorescent Ca super(2+) indicato...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1996-01, Vol.93 (18), p.9527-9532
Main Authors: Issa, N P, Hudspeth, A J
Format: Article
Language:English
Subjects:
Freshwater
Rana catesbeiana
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Summary:Neurotransmitter is released when Ca super(2+) triggers the fusion of synaptic vesicles with the plasmalemma. To study factors that regulate Ca super(2+) concentration at the presynaptic active zones of hair cells, we used laser-scanning confocal microscopy with the fluorescent Ca super(2+) indicator fluo-3. The experimental results were compared with the predictions of a model of presynaptic Ca super(2+) concentration in which Ca super(2+) enters a cell through a point source, diffuses from the entry site, and binds to fixed or mobile Ca super(2+) buffers. The observed time course and magnitude of fluorescence changes under a variety of conditions were well fit when the model included mobile molecules as the only Ca super(2+) buffer. The results confirm the localized entry of Ca super(2)+ underlying neurotransmitter release and suggest that Ca super(2+) is cleared from an active zone almost exclusively by mobile buffer.
ISSN:0027-8424