Modulation by caffeine of calcium-release microdomains in frog skeletal muscle fibers.
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.
Vergara
Julio L
JL
Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles (UCLA), Los Angeles, CA 90095-1751, USA. jvergara@mednet.ucla.edu
Difranco
Marino
M
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D004594:Electrophysiology; D021962:Membrane Microdomains; D008564:Membrane Potentials; D008856:Microscopy, Fluorescence; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011892:Rana catesbeiana; D013997:Time Factors
D000697:Central Nervous System Stimulants; D002110:Caffeine; D002118:Calcium