Ca(2+) dynamics in the lumen of the endoplasmic reticulum in sensory neurons: direct visualization of Ca(2+)-induced Ca(2+) release triggered by physiological Ca(2+) entry.
In cultured rat dorsal root ganglia neurons, we measured membrane currents, using the patch-clamp whole-cell technique, and the concentrations of free Ca(2+) in the cytosol ([Ca(2+)](i)) and in the lumen of the endoplasmic reticulum (ER) ([Ca(2+)](L)), using high- (Fluo-3) and low- (Mag-Fura-2) affinity Ca(2+)-sensitive fluorescent probes and video imaging. Resting [Ca(2+)](L) concentration varied between 60 and 270 microM. Activation of ryanodine receptors by caffeine triggered a rapid fall in [Ca(2+)](L) levels, which amounted to only 40--50% of the resting [Ca(2+)](L) value. Using electrophysiological depolarization, we directly demonstrate the process of Ca(2+)-induced Ca(2+) release triggered by Ca(2+) entry through voltage-gated Ca(2+) channels. The amplitude of Ca(2+) release from the ER lumen was linearly dependent on I(Ca).
Solovyova
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N
The University of Manchester, School of Biological Sciences, 1.124 Stopford Building, Oxford Road, Manchester M13 9PT, UK.
Veselovsky
N
N
Toescu
E C
EC
Verkhratsky
A
A
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000502:physiology; D020013:Calcium Signaling; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism
D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine; D002118:Calcium