whole cell resistance

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zang
zang's picture
whole cell resistance

I am working with CHO cell line (hERG transfected). My internal (KCl based) and external (NaCl based) solutions are very standard.

1: I achieve G-seal. But mostly <1G Ohms. Several 100 M Ohms.
2: I rupture the patch membrane to the whole cell configuration. The membrane resistance>a few G ohms.

Thus, once the patch membrane is ruptured, the resistance value gets increased. Is this normal behavior? (I imagine opposite?). 

The FFM
The FFM's picture
If you are getting mostly <1

If you are getting mostly <1 GOhm then youare NOT acheiving a gigaseal in the first place!

100Mohms is not good enough before you go whole cell.

The phenomenon you describe when you try to go whole cell sounds like to are somehow pulling off a patch off from cell that is then blocking your tip and creating a clog that looks like a giga seal or making an excised patch of some sort.

OR 

you are not at gigseal to start with but then form one when trying to go whole cell by sucking more, even though you are trying to rupture the patch.  If you use the Zap function on your amplifier can you then go whole cell?

Can you try and upload images of you seal tests during and after Gigaseal formation  and during going whole cell and after whole cell.

The FFM
The FFM's picture
FYI

FYI

for hERG in CHO I always used Potassium Gluconate in my pipette. 

I got better seals, help the whole cell patch longer and if the hERG currents were large KCL in the pipette seemed to activate another strange Chloride current at some voltages.  Gluconate does not permeate the Cl channels so is much better for hERG in CHO

zang
zang's picture
Thanks for your advises.

Thanks for your advises.
I use Zap function and it works. I can record typical currents as been seen in the literatures. Also the leak current is small enough (about -30 to -60 pA).  So, anyway, I guess I am recording targeting currents.
I will try to use K-gluconate instead of KCl.