Activity dependent conductances in a neuron model (Liu et al. 1998)

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"... We present a model of a stomatogastric ganglion (STG) neuron in which several Ca2+-dependent pathways are used to regulate the maximal conductances of membrane currents in an activity-dependent manner. Unlike previous models of this type, the regulation and modification of maximal conductances by electrical activity is unconstrained. The model has seven voltage-dependent membrane currents and uses three Ca2+ sensors acting on different time scales. ... The model suggests that neurons may regulate their conductances to maintain fixed patterns of electrical activity, rather than fixed maximal conductances, and that the regulation process requires feedback systems capable of reacting to changes of electrical activity on a number of different time scales."
1 . Liu Z, Golowasch J, Marder E, Abbott LF (1998) A model neuron with activity-dependent conductances regulated by multiple calcium sensors. J Neurosci 18:2309-20 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s):
Channel(s): I Na,t; I L high threshold; I T low threshold; I A; I K; I K,Ca; I Potassium;
Gap Junctions:
Simulation Environment: NEURON;
Model Concept(s): Bursting; Temporal Pattern Generation; Homeostasis;
Implementer(s): Morse, Tom [Tom.Morse at];
Search NeuronDB for information about:  I Na,t; I L high threshold; I T low threshold; I A; I K; I K,Ca; I Potassium;
// init.hoc
// Liu et al. 1998 (activity dependent conductances)
// implemented by Tom Morse 20070807

create soma
access soma

// see p.2318-2319 for parameters

// typicall stg cell morphology p2319:
L=400 // microns
diam=50 // diameter

// leak current not activity dependent p.
insert pas
g_pas =0.01 // (uS/nF) 
e_pas = -50

// Ca diffusion (decay of accumulated intracellular Ca)
// is not activity dependent
insert cad

// these seven conductances are activity dependent:

insert cas
insert cat
insert h
insert ka
insert kca
insert kd
insert na

// insert the mechanisms for activity dependent intrinsic conductances
// first the conductance equations (3)

insert gbara
insert gbarcas
insert gbarcat
insert gbarh
insert gbarkca
insert gbarkd
insert gbarna

// secondly the fast, slow and direct current Ca sensors they depend on

insert F
insert S
insert D

// Set the pointers that define the dynamical system of paper eqn's
// 3 through 7 and figure 10 table.  These pointers link the Ca
// sensors to the conductances and the conductances to the currents

// the first setpointer argument is the pointer, the second, what it
// points to:

setpointer soma.F_gbara(0.5), soma.F_F(0.5)
setpointer soma.S_gbara(0.5), soma.S_S(0.5)
setpointer soma.D_gbara(0.5), soma.D_D(0.5)

setpointer soma.F_gbarcas(0.5), soma.F_F(0.5)
setpointer soma.S_gbarcas(0.5), soma.S_S(0.5)
setpointer soma.D_gbarcas(0.5), soma.D_D(0.5)

setpointer soma.F_gbarcat(0.5), soma.F_F(0.5)
setpointer soma.S_gbarcat(0.5), soma.S_S(0.5)
setpointer soma.D_gbarcat(0.5), soma.D_D(0.5)

setpointer soma.F_gbarh(0.5), soma.F_F(0.5)
setpointer soma.S_gbarh(0.5), soma.S_S(0.5)
setpointer soma.D_gbarh(0.5), soma.D_D(0.5)

setpointer soma.F_gbarkca(0.5), soma.F_F(0.5)
setpointer soma.S_gbarkca(0.5), soma.S_S(0.5)
setpointer soma.D_gbarkca(0.5), soma.D_D(0.5)

setpointer soma.F_gbarkd(0.5), soma.F_F(0.5)
setpointer soma.S_gbarkd(0.5), soma.S_S(0.5)
setpointer soma.D_gbarkd(0.5), soma.D_D(0.5)

setpointer soma.F_gbarna(0.5), soma.F_F(0.5)
setpointer soma.S_gbarna(0.5), soma.S_S(0.5)
setpointer soma.D_gbarna(0.5), soma.D_D(0.5)

// now link the current conductances to the state conductances

setpointer soma.gbar_ka(0.5), soma.gbara_gbara(0.5)
setpointer soma.gbar_cas(0.5), soma.gbarcas_gbarcas(0.5)
setpointer soma.gbar_cat(0.5), soma.gbarcat_gbarcat(0.5)
setpointer soma.gbar_h(0.5), soma.gbarh_gbarh(0.5)
setpointer soma.gbar_kca(0.5), soma.gbarkca_gbarkca(0.5)
setpointer soma.gbar_kd(0.5), soma.gbarkd_gbarkd(0.5)
setpointer soma.gbar_na(0.5), soma.gbarna_gbarna(0.5)


// optional code to play with the effective size of the Ca shell in which the
// entering Ca current is initially placed (by changing the B coeff):
// xpanel("setB")
// xvalue("B","setB_cad",1)
// xpanel()

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