Subcellular calcium transients visualized by confocal microscopy in a voltage-clamped vertebrate neuron.
Confocal laser-scanned microscopy and long-wavelength calcium (Ca2+) indicators were combined to monitor both sustained and rapidly dissipating Ca2+ gradients in voltage-clamped sympathetic neurons isolated from the bullfrog. After a brief activation of voltage-dependent Ca2+ channels, Ca2+ spreads inwardly, and reaches the center of these spherical cells in about 300 milliseconds. Although the Ca2+ redistribution in the bulk of the cytosol could be accounted for with a radial diffusion model, local nonlinearities, suggesting either nonuniform Ca2+ entry or spatial buffering, could be seen. After electrical stimulation, Ca2+ signals in the nucleus were consistently larger and decayed more slowly than those in the cytosol. A similar behavior was observed when release of intracellular Ca2+ was induced by caffeine, suggesting that in both cases large responses originate from Ca2+ release sites near or within the nucleus. These results are consistent with an amplification mechanism involving Ca2(+)-induced Ca2+ release, which could be relevant to activity-dependent, Ca2(+)-regulated nuclear events.
Hernández-Cruz
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Howard Hughes Medical Institute, Department of Neurobiology and Behavior, State University of New York, Stony Brook 11794.
Sala
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F
Adams
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PR
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism; D005456:Fluorescent Dyes; D005728:Ganglia, Sympathetic / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence / Q000379:methods; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D011892:Rana catesbeiana
D015220:Calcium Channels; D005456:Fluorescent Dyes; D002110:Caffeine; D002118:Calcium