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

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Accession:93321
"... 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."
Reference:
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:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Bursting; Temporal Pattern Generation; Homeostasis;
Implementer(s): Morse, Tom [Tom.Morse at Yale.edu];
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;
notes.txt: some odds and ends:

To graph long time scale trajectory of the activity dependent
coefficients, follow these steps:

1) start the model.  

2) Close the voltage graph and hide the multipanel conductance graphs.
   (Graphing while running a simulation in NEURON takes longer than
   displaying the graph at the end.  The voltage trajectory will be
   made invalid by the low number of points plotted per millisecond on
   this run).  Change the Points plotted/ms to 1/60000 (one point
   every minute of simulation time) and the Scrn update interval to 1
   second.  Change tstop to 1e6

3) press Init & Run. Wait till it finishes.

4) click on Window -> nrniv on the NEURON Main Menu to redisplay the
   (previously hidden) conductances graph.

5) Near the bottom of the window titled "Figure 3 Liu, Golowash,
   Marder, Abbott 1998" click the button labeled "View = plot on fig3
   bottom graphs".  Click on the "fig 3 conductance labels" button
   above that.  View the long trajectories in the nrniv window.


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Misc. keywords:

activity patterns: tonic firing, bursting, slow wave Ca spikes

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Computation of the relative Ca shell size between Davison (Bhalla and
Bower) and Liu et al. 1998. From the way that Davison et al. calculate
with B:

cai'=B * ica - (cai-cainf)/tau

there is an implicit factor of tau e.g.

B= b_D/tau_D = -5.18e-2

In Davison tau = tau_D (to keep straight from Liu et al.)=10
In Liu et al. tau=tau_L=20 and B=b_L/tau_L=-.94/20=-4.7e-2

Therefore the b's are
b_D=-.518
b_L=-.94

since b=-(1e4)/(2*FARADAY*depth) i.e. inversely proportional to depth

b_L/b_D = -.94/-.518 = 1.8146718
depth_D/depth_L = 1.8147
depth_L/depth_D = .55

Davison sets depth to 1 um which implies the Liu et al. depth is 
0.55 um.

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