Ca2+ dynamics at the frog motor nerve terminal

Shin ichi Suzuki, Makoto Osanai, Masaki Murase, Naoya Suzuki, Koumin Ito, Tetsuya Shirasaki, Kazuhiko Narita, Kiyoshi Ohnuma, Kenji Kuba, Hiromasa Kijima

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)

Abstract

Rises in free [Ca2+](i) in response to various tetanic stimuli (Ca2+ transient) in frog motor nerve terminals were measured by recording fluorescence changes of Ca2+ indicators and analyzed in relation to short- term synaptic plasticity. Ca2+ transients reached a plateau after 10-20 impulses at 100 Hz and decayed in a three-exponential manner, in which the fast component was predominant. The plateau and fast component of the Ca2+ transient were elevated infralinearly with an increase in tetanus frequency. Computer simulation showed that the Ca2+ transients estimated from fluorescence changes faithfully reflect the true changes in [Ca2+](i) except for the initial 20 ms. A slow Ca2+ chelator, EGTA, loaded into the nerve terminal, decreased the magnitude of both the fast and slow components of facilitation of transmitter release and the time constant of the former. A fast Ca2+ chelator, BAPTA, decreased the magnitude of fast facilitation but slightly increased its time constant. These results suggest that Ca2+ transients in the frog motor nerve terminals are primarily caused by Ca2+ entry and are dissipated by three components, in which the rate of the fast component is equivalent to that of free Ca2+ diffusion. The residual Ca2+ in the nerve terminals after stimulation accounts for the fast component of facilitation.

Original languageEnglish
Pages (from-to)351-365
Number of pages15
JournalPflugers Archiv European Journal of Physiology
Volume440
Issue number3
DOIs
Publication statusPublished - 2000

Keywords

  • BAPTA
  • Ca transient
  • Facilitation
  • Fluorescent Ca indicator
  • Presynaptic terminal
  • Residual calcium
  • Short-term plasticity
  • Transmitter release

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Physiology (medical)

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