[Neuroscience] Re: Help with series resistance and EPSP variations (Jeff II)

Dr. Michael Ferber via neur-sci%40net.bio.net (by Michael.Ferber from gmx.de)
Mon Nov 26 17:21:16 EST 2012

Hi Jeffrey,
> Yes, I am doing current clamp recordings from soma as you mentioned.
> Still I dont get the point how do you conclude that RS is equivalent
> to the resistance of the cytoplasm (Ri).
if I remember correct RS is the sum of all resistances between tip of 
electrode and membrane. This means it is mainly the resistance of the 
cytoplasm + the resistances between the membrane and the ground. (structures 
around the nerve cell, resistance of the bathing solutions and more) Under 
normal conditions these should be constant. In patch clamp experiments the 
cytoplasm may change its resistance due to exchange with the pipette solution.  
So this is the only value that may change. 
> On the other side, how would affect changes in RS the time constant or
> the slope of my EPSP?
In current clamp you record potential changes. If an EPSP is elicited distant 
from your electrode it spreads passively and is damped according to the values 
of membrane resitance membrane capacitance and resistance of the cytoplasm. 
This means the more distant the origin of your EPSP the smaller the amplitude 
and the lower the slope of your EPSP. If you reduce the cytoplasmatic 
resistance  without affecting RM Amplitude and slope of the EPSP  will 
increase compared to the initinal conditions.
> And how will solve the problem the use of a discontinuous mode amplifier?
I do not see any benefit. As far as I know switching modes mainly apply to 
voltage clamp recordings. 
> Thanks again, best wishes
There is also an old thread dealing with these things 
([Neuroscience] Series resistance and capacitance compensation in current 

Best wishes

Dr. Michael Ferber
Gottstreustr. 3
D-34127 Kassel
Tel:(+49) 0561 8165785
mobil: (+49) 01577 3965785
email: Michael.Ferber from gmx.de

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