Digital Imaging of Ca2+ Levels in CNS Neurons under Conditions That Induce Facilitating Increases in Ca2+ Levels and Sustained Ca2+ Elevation
It is generally recognized that intracellular calcium ions (Ca2+) are important in the events that underlie cellular forms of neuronal conditioning. The experimental evidence supporting this view is clearest where there are correlations between electrophysiological and direct optical measurements of calcium fluxes, for example, in invertebrate neurons (Connor and Alkon, 1984; Boyle et al., 1984; Connor et al., 1986). The much smaller size and poor accessibility of vertebrate central nervous system (CNS) neurons have made a cellular analysis of conditioning mechanisms in these systems more difficult. The evidence suggesting that Ca’ ions are involved in changes underlying vertebrate learning has been primarily circumstantial (see, e.g., Lynch and Baudry, 1984). Recently, the development of membrane-permeable Ca2+-sensitive dyes (Tsien, 1980; Grynkiewicz et al.,1985) and high-resolution digital imaging technology have made it possible to measure spatially-resolved free Ca2+ changes in mammalian neurons (Connor, 1986; Connor et al., 1987). At the present time the measurements are optimized using tissue-cultured neurons, where experimental difficulties such as cell inaccessibility, nonspecific optical absorbance, and scattering artifacts can be minimized. However, in the future it should be possible to extend this technology to other preparations, e.g., brain slices.
KeywordsPurkinje Cell Granule Cell Cerebellar Cortex Cerebellar Granule Cell Postnatal Development
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