A kinetic model unifying presynaptic short-term facilitation and depression (Lee et al. 2009)

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"... Here, we propose a unified theory of synaptic short-term plasticity based on realistic yet tractable and testable model descriptions of the underlying intracellular biochemical processes. Analysis of the model equations leads to a closed-form solution of the resonance frequency, a function of several critical biophysical parameters, as the single key indicator of the propensity for synaptic facilitation or depression under repetitive stimuli. This integrative model is supported by a broad range of transient and frequency response experimental data including those from facilitating, depressing or mixed-mode synapses. ... the model provides the reasons behind the switching behavior between facilitation and depression observed in experiments. ..."
1 . Lee CC, Anton M, Poon CS, McRae GJ (2009) A kinetic model unifying presynaptic short-term facilitation and depression. J Comput Neurosci 26:459-73 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Synapse;
Brain Region(s)/Organism:
Cell Type(s): Hippocampus CA1 pyramidal cell; Cerebellum Purkinje cell; Auditory nerve;
Channel(s): I Calcium;
Gap Junctions:
Receptor(s): AMPA;
Transmitter(s): Glutamate;
Simulation Environment: MATLAB; Simulink;
Model Concept(s): Synaptic Plasticity; Facilitation; Depression; Calcium dynamics;
Implementer(s): Lee, Chuang-Chung [chchlee at alum.mit.edu]; Anton, Mihai [mianton at mit.edu]; Poon, Chi-Sang [cpoon at mit.edu]; McRae, Gregory [mcrae at mit.edu];
Search NeuronDB for information about:  Hippocampus CA1 pyramidal cell; Cerebellum Purkinje cell; AMPA; I Calcium; Glutamate;
function [sys,x0] = depression_presyn(time,x,u,flag,xinit)

% ========================================================================
% This file is part of the Supplemental Codes of the manuscript 
% entitled "A Kinetic Model Unifying Presynaptic Short-Term Facilitation 
% and Depression" accepted by Journal of Compuational Neuroscience.  
% (Manucript No. #JCNS583R2).
% Authors: Chuang-Chung J. Lee, Mihai Anton, Chi-Sang Poon, Gregory McRae 
% Created by Chuang-Chung J. Lee 
% Created in July '07.
% Latest modified in Oct. '08.
% ========================================================================

% ------------------------------------------------------------------------
%  This function transforms calcium currents into the flux of glutamate
%  which later on gets converted into Excitatory Postsynaptic Current
%  (EPSC)
%  It be used in a Simulink model as the component of an S Function block
%  Set the S Function name to facilitation_presyn
% Equations used: Eq. (1) - (7)
%  The input vector is the calcium current (ICa)
%  The output vector consists of  
%  1  concentration of bound calcium (Ca)  as well as 
%  2  releasable vesicle ratio (Rrel) 
%  3  release probability (Prel)
%  4  the flux of neurotransmitter (dGlu/dt)
% ------------------------------------------------------------------------

% The number of state, output, and input variables, respectively
zstates = 2;
zoutput = 4;
zinput = 1;

% reaction parameters with fixed values
Ca0=0.02e2*4/1.5; % calcium dynamics
krecov0=1E-4; % recovery rate constants
Prelmax=0.57; % release probability

if (abs(flag) == 1),  %return state derivates
  sys = zeros(zstates, 1);
  Ca = x(1); % conc. of bound calcium
  Rrel = x(2); % releasable vesicle ratio
  %species equations
  sys(1) = (1/TauCa)*(-Ca+Ca0+KCa*u); % conc. of bound calcium
  Prel = Prelmax*Ca.^4./(Ca.^4+Krel.^4); % release probability
  krecov = krecov0+(krecovmax-krecov0)*Ca/(Ca+Krecov); % recovery rate
  sys(2) = krecov*(1-Rrel)- (Prel*Rrel*u); % releasable vesicle ratio

elseif flag == 3,	% return system outputs
  sys(1:2) = x;
  Ca = x(1); % conc. of bound calcium
  Rrel = x(2); % releasable vesicle ratio
  Prel = Prelmax*Ca^4/(Ca^4+Krel^4); % release probability
  sys(3)= Prel;
  sys(4) = (Rrel*Prel*u)*30e5;  %dGlu/dt
elseif flag == 0,	% initial conditions, etc
  sys = [zstates, 0, zoutput, zinput, 0, 1];
  if nargin < 5
    x0(1) = 0.02e2*4/1.5;
    x0(2) = 1;
    x0 = xinit;

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