Theory of Frequency‐Dependent Ion Concentration Changes in Oscillating Electric Fields

1987 ◽  
Vol 134 (5) ◽  
pp. 1112-1117 ◽  
Author(s):  
Martin Blank
Keyword(s):  
Electric Fields ◽  
Ion Concentration ◽  
Frequency Dependent ◽  
Concentration Changes

scholarly journals Electrodiffusion model of synaptic potentials in dendritic spines

2018 ◽  
Author(s):  
Thibault Lagache ◽  
Krishna Jayant ◽  
Rafael Yuste
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Dendritic Spines ◽  
Ionic Currents ◽  
Ion Concentration ◽  
Excitable Cells ◽  
Main Site ◽  
Synaptic Potentials ◽  
Concentration Changes ◽  
Kinetics Of

ABSTRACTWhen modeling electric current flow in neurons and excitable cells, traditional cable theory ignores electrodiffusion (i.e. the interaction between electric fields and ionic diffusion) as it assumes that concentration changes associated with ionic currents are negligible. This assumption, while true for large neuronal compartments, fails when applied to femto-liter size compartments such as dendritic spines - small protrusions that form the main site of synaptic inputs in the brain. Here, we use the Poisson (P) and Nernst-Planck (NP) equations, which relate electric field to charge and couple Fick’s law of diffusion to the electric field, to model ion concentration dynamics in dendritic spines. We use experimentally measured voltage transients from spines with nanoelectrodes to explore these dynamics with realistic parameters. We find that (i) passive diffusion and electrodiffusion jointly affect the kinetics of spine excitatory post-synaptic potentials (EPSPs); (ii) spine geometry plays a key role in shaping EPSPs; and, (iii) the spine-neck resistance dynamically decreases during EPSPs, leading to short-term synaptic facilitation. Our formulation can be easily adopted to model ionic biophysics in a variety of nanoscale bio-compartments.

Ion concentration changes observed in drizzling rains

1997 ◽  
Vol 45 (3) ◽  
pp. 165-182 ◽  
Author(s):  
Hiroaki Minoura ◽  
Yasunobu Iwasaka
Keyword(s):  
Ion Concentration ◽  
Concentration Changes

scholarly journals Relationships between resting conductances, excitability, and t-system ionic homeostasis in skeletal muscle

2011 ◽  
Vol 138 (1) ◽  
pp. 95-116 ◽  
Author(s):  
James A. Fraser ◽  
Christopher L.-H. Huang ◽  
Thomas H. Pedersen
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Conduction Velocity ◽  
Electrical Response ◽  
Quantitative Description ◽  
Ion Concentration ◽  
Ionic Homeostasis ◽  
Voltage Gated ◽  
Concentration Changes ◽  
T System

Activation of skeletal muscle fibers requires rapid sarcolemmal action potential (AP) conduction to ensure uniform excitation along the fiber length, as well as successful tubular excitation to initiate excitation–contraction coupling. In our companion paper in this issue, Pedersen et al. (2011. J. Gen. Physiol. doi:10.1085/jgp.201010510) quantify, for subthreshold stimuli, the influence upon both surface conduction velocity and tubular (t)-system excitation of the large changes in resting membrane conductance (GM) that occur during repetitive AP firing. The present work extends the analysis by developing a multi-compartment modification of the charge–difference model of Fraser and Huang to provide a quantitative description of the conduction velocity of actively propagated APs; the influence of voltage-gated ion channels within the t-system; the influence of t-system APs on ionic homeostasis within the t-system; the influence of t-system ion concentration changes on membrane potentials; and the influence of Phase I and Phase II GM changes on these relationships. Passive conduction properties of the novel model agreed with established linear circuit analysis and previous experimental results, while key simulations of AP firing were tested against focused experimental microelectrode measurements of membrane potential. This study thereby first quantified the effects of the t-system luminal resistance and voltage-gated Na+ channel density on surface AP propagation and the resultant electrical response of the t-system. Second, it demonstrated the influence of GM changes during repetitive AP firing upon surface and t-system excitability. Third, it showed that significant K+ accumulation occurs within the t-system during repetitive AP firing and produces a baseline depolarization of the surface membrane potential. Finally, it indicated that GM changes during repetitive AP firing significantly influence both t-system K+ accumulation and its influence on the resting membrane potential. Thus, the present study emerges with a quantitative description of the changes in membrane potential, excitability, and t-system ionic homeostasis that occur during repetitive AP firing in skeletal muscle.

Local mechanisms of phase-dependent postsynaptic modifications of NMDA-induced oscillations in the abducens motoneurons: a simulation study

1996 ◽  
Vol 76 (2) ◽  
pp. 1015-1024 ◽  
Author(s):  
I. L. Kopysova ◽  
S. M. Korogod ◽  
J. Durand ◽  
S. Tyc-Dumont
Keyword(s):  
Synaptic Input ◽  
Pattern Generation ◽  
Ion Concentration ◽  
Extracellular Potassium ◽  
Pump System ◽  
Voltage Gated ◽  
Ion Concentrations ◽  
Concentration Changes ◽  
Transmembrane Currents

1. In vivo experiments have shown that extracellular microelectrophoretic application of N-methyl-D-aspartate (NMDA) induced oscillatory plateau potentials with bursts of action potentials in rat abducens motoneurons. The period of these slow NMDA oscillations could be altered by single trigeminal non-NMDA excitatory input delivered at low frequency during the NMDA oscillations. 2. A resetting of the oscillations was observed depending on the phase of slow oscillatory cycle during which the trigeminal excitation occurred. 3. We investigated local mechanisms responsible for the phase-dependent modifications of NMDA oscillations, including contributions of voltage and concentration transients, in the mathematical model of the isopotential membrane compartment equipped with voltage-gated Na+, K+, and Ca2+ channels, with Ca2+-dependent K+ channels, and with ligand-gated NMDA and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor channels. The faithful model was constructed with the use of models described earlier, which were modified by increasing time constants of kinetic variables of all voltage-gated conductances and by including coupled dynamics of voltages and ion concentrations. The changes in ion concentrations were produced near the membrane by transmembrane currents and removal mechanisms (pumps, diffusion). 4. This work focuses on local arrangement of voltage- and ligand-gated conductances and on local ion concentration changes in two separate pools: the postsynaptic pool of AMPA receptors and the extrasynaptic pool. In terms of the electrotonic and diffusional length constants, these pools were electrotonically close but diffusionally remote. 5. It was found that the effect of resetting can be produced by a local interaction between plateau and spike-generating conductances and glutamate receptors. 6. In vivo phase-dependent interactions between NMDA oscillations and AMPA synaptic input were reproduced by the local model only when changes in intracellular sodium and extracellular potassium concentrations were taken into account and the mechanisms of ion removal from postsynaptic pools had slower kinetics than the fast pump system operating in the extracellular pool. 7. Postsynaptic changes in ion concentrations of Na+ and K+ in intra- and extracellular layers near the membrane shift of Nernst equilibrium potentials for these ions depending on the phase of activation of synaptic input. Thus Na+ and k+ components of all transmembrane currents involved in the pattern generation are differently affected by synaptic action during the oscillations. We conclude that slow postsynaptic changes in ion concentrations near the membrane play a key role in the resetting of the NMDA oscillations.

Cold-induced cytosolic free calcium ion concentration changes in wheat

2009 ◽  
Vol 166 (17) ◽  
pp. 1955-1960 ◽  
Author(s):  
J. Nagel-Volkmann ◽  
C. Plieth ◽  
D. Becker ◽  
H. Lüthen ◽  
K. Dörffling
Keyword(s):  
Calcium Ion ◽  
Ion Concentration ◽  
Free Calcium ◽  
Cytosolic Free Calcium ◽  
Concentration Changes ◽  
Calcium Ion Concentration

scholarly journals Determination of the zeta potential for highly charged colloidal suspensions

2011 ◽  
Vol 369 (1945) ◽  
pp. 2546-2554 ◽  
Author(s):  
Giovanni Giupponi ◽  
Ignacio Pagonabarraga
Keyword(s):  
Steady State ◽  
Charged Particle ◽  
Zeta Potential ◽  
Electric Fields ◽  
Electrostatic Potential ◽  
Colloidal Suspension ◽  
Colloidal Suspensions ◽  
Ion Concentration ◽  
Lattice Resolution

We compute the electrostatic potential at the surface, or zeta potential ζ , of a charged particle embedded in a colloidal suspension using a hybrid mesoscopic model. We show that, for weakly perturbing electric fields, the value of ζ obtained at steady state during electrophoresis is statistically indistinguishable from ζ in thermodynamic equilibrium. We quantify the effect of counter-ion concentration on ζ . We also evaluate the relevance of the lattice resolution for the calculation of ζ and discuss how to identify the effective electrostatic radius.

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