Can someone provide me some general suggestions on how to solve the unstable baseline issue? I have unstable baseline before putting the pipette into the chamber and no suction at this time point. I grounded my rig, cleaned the chamber, no leakage from the chamber, bleach the electrode. I used one earth (ground) wire, maybe that is not enough for stabilizing the baseline, add one more?
Well, I do whole cell recorgins on brain slices, and to improve baseline stability, I just let the slices rest for at least half an hour (usually I let them rest on aCSF for 1h) before putting them on the rig and starting procedures.
You could also change some ions concentration on your solution, maybe decreasing calcium levels a little bit. However, the most important is to study your cell and your conditions to see what you can or cannot change in your experimental environment to get a good baseline.
Dear Chen Kang: Based on your statement, before electrode was put into the chamber, the electrical circuit must not be closed in loop. The baseline should consequently be unstable or even remain undetected. Once electrode was immersed into the bath, electrical circuit would be established.
What is the amplifier you are using and to what baseline are you referring (current or voltage)? Normally when the electrode is out of the bath you should have virtually infinite resistance between the electrode and ground and baseline (current) should be very stable and close to zero. Do you nave a model cell to check the circuit? And is this a standard patch config ? Have you checked that all your compensation controls are at zero.
Did you check if you have a stable baseline w/o perfusion? If so, you might need to change the position of your ground in the chamber and find a spot where with perfusion you have a stable baseline! I also recommend you to have pellet grounds, you can buy them or make them. They are much more stable.
How does the baseline look like when you have your pipette (with +ve pressure) in the bath with one ground electrode in the same bath? If the bath liquid level or temperature is not fluctuating rapidly, then any further instabilty should be due to in-appropriate chloriding of the electrodes (either or both pipette silver wire and ground). The general noise level, especially the line noise (60Hz in your case) even make it worse if the latter issue is not solved.
Good Luck!
Debanjan
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