Low mobility of the Ca2+ buffers in axons of cultured Aplysia neurons.
Cellular Ca2+ buffers determine amplitude and diffusional spread of neuronal Ca2+ signals. Fixed Ca2+ buffers tend to retard the signal and to lower the apparent diffusion coefficient (D(app)) of Ca2+, whereas mobile buffers contribute to Ca2+ redistribution. To estimate the impact of the expression of specific Ca2+-binding proteins or the errors in Ca2+ measurement introduced by indicator dyes, the diffusion coefficient De and the Ca2+-binding ratio kappa(e) of endogenous Ca2+ buffers must be known. In this study, we obtain upper bounds to these quantities (De < 16 microm2/s; kappa(e) < 60) for axoplasm of metacerebral cells of Aplysia california. Due to these very low values, even minute concentrations of indicator dyes will interfere with the spatiotemporal pattern of Ca2+ signals and will conceal changes in the expression of specific Ca2+-binding proteins, which in the native neuron are expected to have significant effects on Ca2+ signals.
Gabso
M
M
Department of Neurobiology, Life Sciences Institute, The Hebrew University of Jerusalem, Israel.
Neher
E
E
Spira
M E
ME
D000818:Animals; D001048:Aplysia / Q000166:cytology; D001370:Axonal Transport; D001369:Axons / Q000378:metabolism*; D002021:Buffers; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000378:metabolism; D004058:Diffusion; D005456:Fluorescent Dyes / Q000032:analysis* / Q000494:pharmacology; D016257:Fura-2 / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism*; D008845:Microinjections; D009419:Nerve Tissue Proteins / Q000378:metabolism*
D002021:Buffers; D002135:Calcium-Binding Proteins; D002614:Chelating Agents; D005456:Fluorescent Dyes; D009419:Nerve Tissue Proteins; D002118:Calcium; D016257:Fura-2