ISSN:
1432-2013
Keywords:
BAPTA Ca2+ transient Facilitation Fluorescent Ca2+ indicator Presynaptic terminal Residual calcium Short-term plasticity Transmitter release
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240000278
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