[Neuroscience] Re: Junction potential in whole-cell recording

tehgabriel at web.de tehgabriel at web.de
Sun Apr 2 06:43:07 EST 2006

Hi Anup!

You can be sure that there is definitively something wrong when you
obtain a liquid junction potential (LJP) of +56 mV. But I can hardly
imagine how to achieve such a high value. Either there is something
wrong with your solutions or you have an error within your estimation
procedure. But it is hard to pinpoint the source of error without
knowing the exact composition of your solutions and the method how you
measure/calculate the LJP.

An osmolarity of 255 mOsm is very low and you should expect problems in
obtaining proper patches. But osmolarity has no (or only a minor)
impact on the LJP sice this depends on the ionic composition of your
solutions within the pipette and the bath chamber respectively. So
compounds like e.g. glucose which may affect the osmolarity do not
alter the LJP. Certain software tools are freely available (o may be
part of your recording software -> pClamp)  that allow to calculate the
LJP of your system. Just try a google search or got to
[http://web.med.unsw.edu.au/phbsoft/LJP_Calculator.htm]. There you can
also find a brief introduction into the theory of LJPs which might be
helpful for you.

You can correct your data for the LJP but this is not mandatory as long
as you don't forget to state this. A correction simply shifts your data
along the y-axis and does not affect the slope of signals.


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