The Entry and Clearance of Ca2+ at Individual Presynaptic Active Zones of Hair Cells from the Bullfrog's Sacculus

Neurotransmitter is released when Ca2+ triggers the fusion of synaptic vesicles with the plasmalemma. To study factors that regulate Ca2+ concentration at the presynaptic active zones of hair cells, we used laser-scanning confocal microscopy with the fluorescent Ca2+ indicator fluo-3. The experiment...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1996-09, Vol.93 (18), p.9527-9532
Main Authors: Issa, Naoum P., Hudspeth, A. J.
Format: Article
Language:English
Subjects:
Aniline Compounds - metabolism
Animals
Calcium - metabolism
Cell membranes
Depolarization
Egtazic Acid - analogs & derivatives
Egtazic Acid - pharmacology
Fluorescence
Hair cells
Hair Cells, Vestibular - metabolism
Membrane potential
Membrane Potentials
Neurons
Neuroscience
Neurotransmitters
Presynaptic Terminals - metabolism
Rana catesbeiana
Saccule and Utricle - cytology
Saccule and Utricle - metabolism
Sensors
Space life sciences
Synapses
Time Factors
Xanthenes - metabolism
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Summary:Neurotransmitter is released when Ca2+ triggers the fusion of synaptic vesicles with the plasmalemma. To study factors that regulate Ca2+ concentration at the presynaptic active zones of hair cells, we used laser-scanning confocal microscopy with the fluorescent Ca2+ indicator fluo-3. The experimental results were compared with the predictions of a model of presynaptic Ca2+ concentration in which Ca2+ enters a cell through a point source, diffuses from the entry site, and binds to fixed or mobile Ca2+ 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 Ca2+ buffer. The results confirm the localized entry of Ca2+ underlying neurotransmitter release and suggest that Ca2+ is cleared from an active zone almost exclusively by mobile buffer.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.93.18.9527