Model an inhibitory synapse

The basics of how to develop, test, and use models.
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mattions
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Joined: Tue Jul 15, 2008 11:21 am
Location: EMBL-EBI Cambridge UK

Model an inhibitory synapse

Post by mattions »

Hello,
I'm trying to figure out how to model an inhibitory synapse.

I've created an Alpha Synapse and tested with a negative e, but I don't see any hyperpolarization...
How can I achieve that?

And, yes hello (world\n), this is my first post :)
ted
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Re: Model an inhibitory synapse

Post by ted »

What are onset, tau, gmax, e, and v of your model? Too late, too fast, or too small a peak conductance, and you'll see nothing. If e > v you'll get depolarization, e < v and it's hyperpolarization.
mattions
Posts: 65
Joined: Tue Jul 15, 2008 11:21 am
Location: EMBL-EBI Cambridge UK

Re: Model an inhibitory synapse

Post by mattions »

Thanks ted!

I was thinking few millivolts under the the zero will do the trick instead it need to be less than the v.

Actually I've tried using the default parameters of the Alpha synapse so tau 0.1 and gmax 0.05...
Anyway I can see a small hyperpolarization of the membrane where is the synapse..
Usually how much is the e of a inhibitory synapse?
ted
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Re: Model an inhibitory synapse

Post by ted »

Good that you asked. As ACD wrote, "It is a capital mistake to theorize before one has data."

Depends on the permselectivity of the channels, which in turn is correlated with the neurotransmitter, which in turn depends on the nature of the pre- and postsynaptic cells. And even for a particular channel type, the equilibrium potential of the permeant species may depend on the age of the animal, and what part of the dendritic tree the synapse is located in. GABA-A synapses open chloride channels, with potentials within 5-10 mV of rest. GABA-B synapses open potassium channels, with equilibrium potentials 10 or more mV more negative than rest. Time courses also vary, the former being faster than the latter (but nowhere near as fast as the default time course of NEURON's AlphaSynapse). A good place to begin learnign more is chapter 13 of Johnston & Wu's book "Foundations of Cellular Neurophysiology."
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