[Neuroscience] Series resistance and capacitance compensation in current clamp

Dr. Michael Ferber via neur-sci%40net.bio.net (by Michael.Ferber from gmx.de)
Thu Feb 22 15:16:34 EST 2007

> 1. Will this stuff up our membrane potential values during large current
> steps (<1nA)?  In what way?
In voltage clamp(!!!!) the problem is the ratio between RS and the membrane 
resistance. Here you have a voltage-divider. Therefore the membrane potential 
does not corespond to your settings and the mistake depends on the ratio of 
RM and RS. Due to the fact that the RM depends on the number of open channels 
the mistake is not linear and increases with increasing membrane current 
(=decreasing membrane resistance).  If RS is low and RM is high everything is 
fine, but if you have huge membrane currents the real membrane potential may 
be far away from the value you set. 
> 2. Is there any legitimate way we can adjust our data post-hoc?
I see no way.  
> 3. Will compensating make a difference in current clamp for our case?
In this case you apply a constant current and the potential is floating 
freely.... and if you compensate your electrode properly the very fast 
components (RS, pipette resistance ....) should be cancelled anyway.

Capacitance compensation makes your systen faster (simplyfied). This may be of 
interest if you are interested in the kinetics of processes (i.e activation 
of channels) .


Dr. Michael Ferber
Herchenbachstr. 13
D-34253 Lohfelden
Tel:(+49) 0561 8165785
mobil: (+49) 0160 96734843 
email: Michael.Ferber from gmx.de

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