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

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

Jeffrey Lopez-2
Hi Michael, thanks a lot for your comments and the link.
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).
On the other side, how would affect changes in RS the time constant or
the slope of my EPSP?
And how will solve the problem the use of a discontinuous mode amplifier?
Thanks again, best wishes



2012/11/25, [hidden email]
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>    1. Re: Help with series resistance and EPSP variations
>       (Dr. Michael Ferber)
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> Date: Sat, 24 Nov 2012 11:43:18 +0100
> From: "Dr. Michael Ferber" <[hidden email]>
> Subject: Re: [Neuroscience] Help with series resistance and EPSP
> variations
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> Hmm.... hwta type of experiment are you doing? I assume your patchj
> electrode
> is lovcated at the soma and you are in current clamp mode. Your EPSPs are
> eliceted somewhere distant in the dendrites of a neuron. Right? Uner these
> circumstances I would say that your RS is equivalent to the resistance if
> the
> cytoplasm. To solve your question you may have a look to the length constant
>
> of axons (or dendrites).
>
> See for example here: http://neuroscience.uth.tmc.edu/s1/chapter03.html
>
>
> Best wishes
> Michael
>
>> Hi everybody, there is a question I have since some time but still
>> dont have a convinvcing answer.
>> When your series resistance changes during a patch clamp experiment,
>> 1- which influence does it have on my EPSP slope and amplitude?
>> 2-why?
>> 3-how would it help or not to use a discontinuous (switching) amplifier?
>>  If anyone could help me to understand I will appreciate it, please
>> try to be explicit in answering. Thanks a lot in advance!
>>
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> Dr. Michael Ferber
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Re: Re: Help with series resistance and EPSP variations (Jeff II)

Dr. Michael Ferber
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
http://www.bio.net/bionet/mm/neur-sci/2007-February/thread.html#61664 
([Neuroscience] Series resistance and capacitance compensation in current
clamp)


Best wishes
Michael

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Dr. Michael Ferber
Gottstreustr. 3
D-34127 Kassel
Tel:(+49) 0561 8165785
mobil: (+49) 01577 3965785
email: [hidden email]

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