ISSN:
1432-2013
Keywords:
Intracellular calcium concentration
;
Spatial inhomogeneity
;
Ca2+ load and recovery
;
Internal Ca2+ stores
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Digital imaging of fura-2 fluorescence and the voltage-clamp technique were combined to study cytoplasmic free Ca2+ concentration, [Ca]i, in neurons cultured from chick dorsal root ganglia. Depolarizing pulses raised [Ca]i to a new steady-state level which was achieved earlier in neurites than in the soma. The rise in [Ca]i during stimulated bursting or rhythmic activity was also faster in neurites. After stimulation [Ca]i recovered monoexponentially in the soma and biexponentially in neurites. Application of 50 mM KCl produced membrane depolarization and a concomitant increase of [Ca]i. During wash-out [Ca]i often declined to an intermediate steady-state level at which it stayed for several minutes. Thereafter the resting level of [Ca]i was quickly restored. [Ca]i recovery was delayed after treating the cell with 2 μM thapsigargin, an inhibitor of the Ca2+ pump of internal Ca2+ stores. Caffeine (10 mM) transiently increased [Ca]i. A second caffeine application produced smaller [Ca]i changes due to the prior depletion of Ca2+ stores, which could be replenished by brief exposure to KCl. Thapsigargin (2 μM) transiently increased [Ca]i both in the standard and Ca2+-free solution. [Ca]i transients due to caffeine and thapsigargin started in the cell interior, in contrast to [Ca]i changes evoked by membrane depolarization, which were noticed first at the cell edge. Caffeine and thapsigargin induced a transient inward current which persisted in the presence of 1 mM La3+ and in Ca2+-free solutions, but which was greatly diminished in Na+-free solutions. The effects of caffeine and thapsigargin were mutually exclusive both in the generation of [Ca]i transients and in the inward current induction.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374610
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