%0 Journal Article %1 Coll_1999_117 %A Collier, M. L. %A Thomas, A. P. %A Berlin, J. R. %D 1999 %J J. Physiol. %K 10066927 Algorithms, Aniline Animal, Blockers, Cadmium, Calcium Calcium, Channel Channels, Compounds, Confocal, Dyes, Fluorescent Gov't, Heart In L-Type, Male, Membrane Microscopy, Myocardium, Nifedipine, Non-U.S. P.H.S., Patch-Clamp Potentials, Rats, Research Reticulum, Sarcoplasmic Signaling, Sprague-Dawley, Support, Techniques, U.S. Ventricles, Vitro, Xanthenes, s, %P 117--128 %T Relationship between L-type Ca$^2+$ current and unitary sarcoplasmic reticulum Ca$^2+$ release events in rat ventricular myocytes. %U http://jp.physoc.org/cgi/content/full/516/1/117 %V 516 ( Pt 1) %X 1. The time courses of Ca$^2+$ current and Ca$^2+$ spark occurrence were determined in single rat ventricular myocytes voltage clamped with patch pipettes containing 0.1 microM fluo-3. Acquisition of line-scan images on a laser scanning confocal microscope was synchronized with measurement of Cd2+-sensitive Ca$^2+$ currents. In most cells, individual Ca$^2+$ sparks were observed by reducing Ca$^2+$ current density with nifedipine (0.1-8 microM). 2. Ca$^2+$ sparks elicited by depolarizing voltage-clamp pulses had a peak Ca$^2+$ amplitude of 289 +/- 3 nM with a decay half-time of 20.8 +/- 0.2 ms and a full width at half-maximum of 1.40 +/- 0.03 microm (mean +/- s. e.m., n = 345), independent of the membrane potential. 3. The time between the beginning of a depolarization and the initiation of each Ca$^2+$ spark was calculated and data were pooled to construct waiting time histograms. Exponential functions were fitted to these histograms and to the decaying phase of the Ca$^2+$ current. This analysis showed that the time constants describing Ca$^2+$ current and Ca$^2+$ spark occurrence at membrane potentials between -30 mV and +30 mV were not significantly different. At +50 mV, in the absence of nifedipine, the time constant describing Ca$^2+$ spark occurrence was significantly larger than the time constant of the Ca$^2+$ current. 4. A simple model is developed using Poisson statistics to relate macroscopic Ca$^2+$ current to the opening of single L-type Ca$^2+$ channels at the dyad junction and to the time course of Ca$^2+$ spark occurrence. The model suggests that the time courses of macroscopic Ca$^2+$ current and Ca$^2+$ spark occurrence should be closely related when opening of a single L-type Ca$^2+$ channel initiates a Ca$^2+$ spark. By comparison with the data, the model suggests that Ca$^2+$ sparks are initiated by the opening of a single L-type Ca$^2+$ channel at all membrane potentials encountered during an action potential.

@article{Coll_1999_117, abstract = {1. The time courses of {C}a$^{2+}$ current and {C}a$^{2+}$ spark occurrence were determined in single rat ventricular myocytes voltage clamped with patch pipettes containing 0.1 microM fluo-3. Acquisition of line-scan images on a laser scanning confocal microscope was synchronized with measurement of Cd2+-sensitive {C}a$^{2+}$ currents. In most cells, individual {C}a$^{2+}$ sparks were observed by reducing {C}a$^{2+}$ current density with nifedipine (0.1-8 microM). 2. {C}a$^{2+}$ sparks elicited by depolarizing voltage-clamp pulses had a peak [{C}a$^{2+}$] amplitude of 289 +/- 3 nM with a decay half-time of 20.8 +/- 0.2 ms and a full width at half-maximum of 1.40 +/- 0.03 microm (mean +/- s. e.m., n = 345), independent of the membrane potential. 3. The time between the beginning of a depolarization and the initiation of each {C}a$^{2+}$ spark was calculated and data were pooled to construct waiting time histograms. Exponential functions were fitted to these histograms and to the decaying phase of the {C}a$^{2+}$ current. This analysis showed that the time constants describing {C}a$^{2+}$ current and {C}a$^{2+}$ spark occurrence at membrane potentials between -30 mV and +30 mV were not significantly different. At +50 mV, in the absence of nifedipine, the time constant describing {C}a$^{2+}$ spark occurrence was significantly larger than the time constant of the {C}a$^{2+}$ current. 4. A simple model is developed using Poisson statistics to relate macroscopic {C}a$^{2+}$ current to the opening of single L-type {C}a$^{2+}$ channels at the dyad junction and to the time course of {C}a$^{2+}$ spark occurrence. The model suggests that the time courses of macroscopic {C}a$^{2+}$ current and {C}a$^{2+}$ spark occurrence should be closely related when opening of a single L-type {C}a$^{2+}$ channel initiates a {C}a$^{2+}$ spark. By comparison with the data, the model suggests that {C}a$^{2+}$ sparks are initiated by the opening of a single L-type {C}a$^{2+}$ channel at all membrane potentials encountered during an action potential.}, added-at = {2009-06-03T11:20:58.000+0200}, author = {Collier, M. L. and Thomas, A. P. and Berlin, J. R.}, biburl = {https://www.bibsonomy.org/bibtex/2d2edb57630d13f2cf80e8f9dc697db00/hake}, description = {The whole bibliography file I use.}, file = {Coll_1999_117.pdf:Coll_1999_117.pdf:PDF}, interhash = {fc4f3b2367fdb3ab8064020d084cc170}, intrahash = {d2edb57630d13f2cf80e8f9dc697db00}, journal = {J. Physiol.}, keywords = {10066927 Algorithms, Aniline Animal, Blockers, Cadmium, Calcium Calcium, Channel Channels, Compounds, Confocal, Dyes, Fluorescent Gov't, Heart In L-Type, Male, Membrane Microscopy, Myocardium, Nifedipine, Non-U.S. P.H.S., Patch-Clamp Potentials, Rats, Research Reticulum, Sarcoplasmic Signaling, Sprague-Dawley, Support, Techniques, U.S. Ventricles, Vitro, Xanthenes, s,}, month = Apr, pages = {117--128}, pmid = {10066927}, timestamp = {2009-06-03T11:21:08.000+0200}, title = {Relationship between L-type {C}a$^{2+}$ current and unitary sarcoplasmic reticulum {C}a$^{2+}$ release events in rat ventricular myocytes.}, url = {http://jp.physoc.org/cgi/content/full/516/1/117}, volume = {516 ( Pt 1)}, year = 1999 }