Modal gating in neuronal and skeletal muscle ryanodine-sensitive Ca2+ release channels
Armisén, R.; Sierralta, J.; Vélez, P.; Naranjo, D.; Suárez-Isla, B.A.
American Journal of Physiology 271(1 Pt 1): C144-C153
1996
ISSN/ISBN: 0002-9513 PMID: 8760040 Document Number: 459984
The bursting behavior of ryanodine-sensitive single Ca-2+ release channels present in chicken cerebellum endoplasmic reticulum (ER), rat hippocampus ER, and frog and rabbit skeletal muscle sarcoplasmic reticulum was established. Unconditional dwell time distributions fitted by the maximum likelihood method reveal at least three open and closed exponential components. Trains of low open probability (P.) bursts were interspersed with trains of high P-o bursts ( gtoreq 0.8) in all the ryanodine receptor isotypes tested. The gating kinetics of the Ca-2+ release channels were defined in long recordings by analyzing burst sequences and gamma distributions of average intraburst open (T-o) and closed times (T-c). The gamma distributions of T-o had two gamma components, suggesting the existence of two distinct burst types. In contrast, the gamma distributions of T-o had only one component. The correlation between consecutive burst pairs was defined in terms of T-o and then statistically tested by 2 times 2 matrix contingency analysis. The probability that the ubiquitous sequential burst pattern was generated by random occurrence was lt 0.01 (two-tailed Fisher's exact test). Temporal correlations were observed in all ryanodine receptor isotypes under a variety of experimental conditions. These data strongly suggest that single Ca-2+ release channels switch slowly between modes of gating. We propose that the effects of agonists of Ca-2+ release channels such as Ca-2+ itself can be explained as concentration-dependent changes in the availability of each mode.