Recently I started to work with hippocampal slices. I use Axopatch 200B, Clampex 9.2. After I reached gigaseal it becomes extremly unstable, baseline begins to shake finely (it's not a 50 Hz, it's a tiny random, unsystematic shaking with almost indistinguishable amplitude), and after a few seconds baseline drops down, I'm loosing the seal at all. It happens every time I've got a seal. Could please somebody explain why is seal unstable and what to do to get stable seal and whole-cell on hippocampal slices?
Another problem is that I cannot define the REAL resistance of my glass pipettes. If to take two pipettes made from one capillary, on my setup one of them has 11 MOhm but on the another rig (also with Axopatch 200B and Clampex 9.2) the second pipette from this pair shows only 6-7 MOhm. I used the same model of the cell on these both setups and it showed equal parameters on both. Where could be the problem?
Any suggestions concerning either of problems will be greatly appreciated.