tomte <tehgabriel at web.de> wrote:
> I use pipettes with the same parameters (3MOhm, K-Gluc.) and they work
> perfectly. But sure it may be one point you can check. Usually
> increasing the pipette resistance (up to 5-6 MOhm, don't go higher)
> will result in getting better seals but your access resistance gets
Of course the pipette resitance alone is not necessarily a suffient
description of the pipettes. Remembering things which have been a
problem in my work I would recommend having a good look at the tips:
-are the surfaces where the glass tore smooth or do they appear rough
-what is the geometry of the pipettes? Just conical or are they formed
slightly more parabolic?
There is a good chapter on tip geometry in "Single Channel Recording"
Though, reading the rest of the OPs Post, I have the impression, that
the tips are not the issue here. The despcription he gives sounds more
like he's patching "gunk" instead of cells. I have very little
experience with blind patching (which is what he appears to be trying),
but believe to remember, that there should be a more drastic change in
the current response to the test-pulse when the pipette opening is close
to a cell.