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. 1996 Dec 15;497(Pt 3):581–588. doi: 10.1113/jphysiol.1996.sp021791

Repriming and activation alter the frequency of stereotyped discrete Ca2+ release events in frog skeletal muscle.

A Lacampagne 1, W J Lederer 1, M F Schneider 1, M G Klein 1
PMCID: PMC1160956  PMID: 9003545

Abstract

1. Brief localized elevations in myoplasmic [Ca2+] (Ca2+ sparks) in individual sarcomeres of voltage-clamped frog skeletal muscle fibres were examined by laser scanning confocal microscopy. 2. Fibres held at 0 mV were briefly repolarized to -90 mV (repriming pulse) to restore only a small fraction of sarcoplasmic reticulum (SR) calcium release. Subsequent depolarization to 0 mV (test pulse) caused the appearance of small numbers of Ca2+ sparks at different sarcomeres from pulse to pulse. Increasing the repriming time resulted in an increase in the frequency of occurrence of the Ca2+ sparks. 3. The amplitude and spatio-temporal extent of the Ca2+ sparks were independent of the repriming time and test pulse voltage. Ca2+ sparks recorded during small depolarizations of fibres held at -90 mV had a similar amplitude and spatio-temporal extent as those recorded after brief repriming of the same fibre held at 0 mV. 4. We conclude that stereotyped Ca2+ sparks underlie calcium release at all voltages and all extents of repriming. The amplitude of Ca2+ release is thus graded by the frequency but not by the amplitude or spatio-temporal extent of the individual SR Ca2+ release events.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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