Short-term changes in the Ca2+-exocytosis relationship during repetitive pulse protocols in bovine adrenal chromaffin cells

Kathrin L. Engisch, Natalya I. Chernevskaya, Martha C. Nowycky

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Stimulus-secretion coupling was monitored with capacitance detection in bovine chromaffin cells recorded in perforated patch mode and stimulated with trains of depolarizing pulses. A subset of stimulus trains evoked a response with a Ca2+-exocytosis relationship identical to that obtained for single depolarizing pulses (Engisch and Nowycky, 1996). Other trains evoked responses with enhanced or diminished Ca2+ efficacy relative to this input- output function. The probability of obtaining a particular Ca2+-exocytosis relationship was correlated with the amount of Ca2+ entry per pulse, such that shorter pulses or smaller currents were associated with the greatest efficacy, and longer pulses and larger currents with the lowest efficacy. Apparent enhancements in Ca2+ efficacy were not caused by residual Ca2+ summing between pulses, because decreasing the interval between pulses usually reduced efficacy in the same cell; conversely, increasing the interval between pulses did not prevent an enhanced Ca2+-exocytosis relationship. Apparent decreases in Ca2+ efficacy were not caused by depletion of an available pool of release-ready vesicles, because an equivalent amount of total Ca2+ entry during a single long depolarizing pulse usually evoked a much larger secretory response in the same cell. Finally, there were no striking differences in global Ca2+ levels monitored with the fluorescent indicator Fura Red that could account for apparent changes in Ca2+ efficacy during repetitive stimulus protocols. It appears that in chromaffin cells, the Ca2+-exocytosis relationship is subject to activity-dependent changes during a stimulus train and can be modulated up or down from a basal state accessed by single pulse stimulations.

Original languageEnglish (US)
Pages (from-to)9010-9025
Number of pages16
JournalJournal of Neuroscience
Volume17
Issue number23
DOIs
StatePublished - 1997
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)

Keywords

  • Amperometry
  • Ca measurements
  • Capacitance detection
  • Catecholamines
  • Depression
  • Facilitation
  • Large dense-cored vesicles
  • Residual calcium
  • Stimulus-secretion coupling
  • Synaptic plasticity
  • Vesicle pools

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