Rapid kinetics of depolarization-induced changes in intrasynaptosomal calcium concentrations.
The rapid kinetics of depolarization-evoked calcium influxes in isolated nerve terminals from rat cortex were monitored by stopped-flow spectrofluorimetry using specific indicators (Fluo-3, Indo-1). A very rapid increase in the intrasynaptosomal Ca(2+)-level was detected within the subsecond time range after depolarizing synaptosomes by mixing with physiological saline containing elevated K(+)-concentrations. About 15 mM [K+]o was determined as threshold concentration for inducing Ca(2+)-influx, which increased with higher concentration and saturated at [K+]o-concentrations of about 40 mM [K+]o.
Tareilus
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University of Stuttgart-Hohenheim, Institute of Zoophysiology, Fed. Rep. Germany.
Breer
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H
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism*; D005456:Fluorescent Dyes; D007211:Indoles; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009411:Nerve Endings / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D014966:Xanthenes
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D007211:Indoles; D014966:Xanthenes; C059587:Indo-1 pentaacetoxymethyl ester; C059715:Fluo-3; D011188:Potassium; D002118:Calcium