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Biological Research

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VERGARA, JULIO L  and  DIFRANCO, MARINO. Modulation by caffeine of calcium-release microdomains in frog skeletal muscle fibers. Biol. Res. [online]. 2006, vol.39, n.3, pp.567-581. ISSN 0716-9760.

The effects of caffeine on the process of excitation-contraction coupling in amphibian skeletal muscle fibers were investigated using the confocal spot detection technique. This method permits to carefully discriminate between caffeine effects on the primary sources of Ca2+ release at the Z-lines where the triads are located and secondary actions on other potential Ca Release sources. Our results demonstrate that 0.5 mM caffeine potentiates and prolongs localized action-potential evoked Ca2+ transients recorded at the level of the Z-lines, but that 1mM only prolongs them. The effects at both doses are reversible. At the level of the M-line, localized Ca2+ transients displayed more variability in the presence of 1 mM caffeine than in control conditions. At this dose of caffeine, extra-junctional sources of Ca2+ release also were observed occasionally.

Keywords : excitation-contraction coupling; caffeine; confocal spot detection; calcium transients; frog skeletal muscle; calcium microdomains.

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