Abstract
Calcium ions are an important second messenger in living cells. Indeed
calcium signals in the form of waves have been the subject of much
recent experimental interest. It is now well established that these
waves are composed of elementary stochastic release events (calcium
puffs or sparks) from spatially localised calcium stores. The aim
of this paper is to analyse how the stochastic nature of individual
receptors within these stores combines to create stochastic behaviour
on long time-scales that may ultimately lead to waves of activity
in a spatially extended cell model. Techniques from asymptotic analysis
and stochastic phase-plane analysis are used to show that a large
cluster of receptor channels leads to a release probability with
a sigmoidal dependence on calcium density. This release probability
is incorporated into a computationally inexpensive model of calcium
release based upon a stochastic generalisation of the fire-diffuse-fire
(FDF) threshold model. Numerical simulations of the model in one
and two dimensions (with stores arranged on both regular and disordered
lattices) illustrate that stochastic calcium release leads to the
spontaneous production of calcium sparks that may merge to form saltatory
waves. Illustrations of spreading circular waves, spirals and more
irregular waves are presented. Furthermore, receptor noise is shown
to generate a form of array enhanced coherence resonance whereby
all calcium stores release periodically and simultaneously.
- 15142744
- action
- animals,
- atpase,
- biological,
- calcium
- calcium,
- cardiac,
- cardiovascular,
- cell
- cells,
- channel
- channel,
- channels,
- comparative
- computer
- computing,
- conduction,
- contraction,
- cultured,
- electrophysiology,
- enzyme
- gating,
- gov't,
- heart
- heart,
- humans,
- inhibitors,
- ion
- l-type,
- magnetics,
- mathematical
- membrane
- membrane,
- models,
- muscle
- myocardial
- myocytes,
- neural
- neurological,
- neurons,
- non-u.s.
- p.h.s.,
- potentials,
- processes,
- rate,
- rats,
- receptor
- release
- research
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