SEClamp for cable model

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BVGH
Posts: 2
Joined: Fri Nov 03, 2017 4:12 pm

SEClamp for cable model

Hi,

I am not sure if it is a weird question or not. Does it make sense to apply the voltage clamp, using "SEClamp", to the first compartment and measure the current response of the last compartment (ic, capacitor current) instead of the current of SEClamp in the first compartment? By doing this, I want to get the I-V curve for voltage clamping.

Thanks.
ted
Posts: 5819
Joined: Wed May 18, 2005 4:50 pm
Location: Yale University School of Medicine
Contact:

Re: SEClamp for cable model

Usually voltage clamp is used to measure currents carried by ion channels. For measurements to be most useful, (1) the channels must close to the location of the clamp, where membrane potential is under best control, and (2) the recorded currents should be as free of capacitive current as possible. These requirements are best met in cells that are anatomically compact (and therefore electrotonically compact). If a cell has sufficient spatial extent that it must be represented by multiple compartments in order to get good spatial accuracy, then the clamp current is of questionable use as a means for studying the properties of the ion channels. Also, it is not useful to record membrane capacitive current, because the experimental question is not "how does membrane capacitive current depend on membrane potential and time"--the question is "how does a particular ionic current depend on membrane potential and time."
BVGH
Posts: 2
Joined: Fri Nov 03, 2017 4:12 pm

Re: SEClamp for cable model

Thank you, Ted.

One more question. For modeling in NEURON, If we have both voltage-clamp and current-clamp results from bouton, so that the clamping was done in bouton and the channels responsible for the action potential are located at 30um from bouton, is it better to use voltage-clamp results or current-clamp results? No channel was blocked but we know the types of ion channels in this neuron.

One more thing. Does it make sense to calculate Cm, Rm, and Ra for this model by using the sum of all areas (area_bouton+area_unmylinated part) or we have to only consider the area of bouton (where we applied voltage clamp in the experiment)?
ted