Spatial and temporal control of intracellular free Ca2+ in chick sensory neurons

Pflugers Arch. 1993 Jul;424(2):183-91. doi: 10.1007/BF00374610.


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 microM 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 microM) transiently increased [Ca]i both in the standard and Ca(2+)-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 Ca(2+)-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.

MeSH terms

  • Animals
  • Caffeine / pharmacology
  • Calcium / metabolism*
  • Calcium Channels / drug effects
  • Calcium Channels / metabolism
  • Calcium-Transporting ATPases / antagonists & inhibitors
  • Cells, Cultured
  • Chick Embryo
  • Electrophysiology
  • Ganglia, Spinal / cytology
  • Ganglia, Spinal / drug effects
  • Ganglia, Spinal / metabolism
  • Neurites / drug effects
  • Neurites / metabolism
  • Neurons, Afferent / drug effects
  • Neurons, Afferent / metabolism*
  • Potassium Chloride / pharmacology
  • Spectrometry, Fluorescence
  • Terpenes / pharmacology
  • Thapsigargin


  • Calcium Channels
  • Terpenes
  • Caffeine
  • Potassium Chloride
  • Thapsigargin
  • Calcium-Transporting ATPases
  • Calcium