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.
%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
}