Ca2+ dynamics in the lumen of the endoplasmic reticulum in sensory neurons: direct visualization of Ca2+-induced Ca2+ release triggered by physiological Ca2+ entry

AUTOR(ES)

Solovyova, N.

FONTE

Oxford University Press

RESUMO

In cultured rat dorsal root ganglia neurons, we measured membrane currents, using the patch–clamp whole-cell technique, and the concentrations of free Ca2+ in the cytosol ([Ca2+]i) and in the lumen of the endoplasmic reticulum (ER) ([Ca2+]L), using high- (Fluo-3) and low- (Mag-Fura-2) affinity Ca2+-sensitive fluorescent probes and video imaging. Resting [Ca2+]L concentration varied between 60 and 270 µM. Activation of ryanodine receptors by caffeine triggered a rapid fall in [Ca2+]L levels, which amounted to only 40–50% of the resting [Ca2+]L value. Using electrophysiological depolarization, we directly demonstrate the process of Ca2+-induced Ca2+ release triggered by Ca2+ entry through voltage-gated Ca2+ channels. The amplitude of Ca2+ release from the ER lumen was linearly dependent on ICa.

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