[Neuroscience] Measuring transmembrane voltages - Sources of error and perforated patching

Bill via neur-sci%40net.bio.net (by connelly.bill from gmail.com)
Fri Oct 3 18:07:40 EST 2008


Hi,

To get to the point I finally have got gramicidin perforated patching
working regularly (~30mOhms in 15 minutes) however all my cells appear
to be "resting" ~20mV more hypoerpolarized than they do when I do
whole-cell recording using either a K-gluconate or KCl based pipette
solution. Does this make sense to anyone?

I presume this is something to do with the fact that during whole-cell
recordings the cell interior eventually becomes the same as your
pipette solution and hence there is no liquid junction potential (so
the added voltage which was 'bucked' out of the system when the
electrode was zeroed and the LJP was in force, and is added to your
recorded membrane potential)? However in perforated patch mode, you
have a difference situation, where different ions have different
mobilities, not only based on their mobilities in solution, but their
conductivity through the gramicidin pores? Or am I over analysing
stuff here?



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