Hi all, I am seeking for your help with the multiclamp 700B. I am using it for patch clamp in hippocampal neurons. And sometimes when I did pipette offset, the holding voltage just suddenly changed to a weird value (+40 mV). Yet this problem had not been too terrible since I just needed to either restart the program or did pipette offset again.
However, since yesterday this program seemed to behaved terribly. The holding voltage kept jumping anytime I did pipette offset to random values (0, 40, 51 mV) and when I unclicked the "holding" on the multiclamp window, it showed overloading values in the holding current. Restarting the program and the whole computer did not help.
Did any of you have a hint of what could cause the problem? And how should I fix it?
Thanks so much!
You could try to change your reference electrode or re-chloride it depending on the type you use. It could also be the slice chamber, that is making a short circuit - try to clean it or try with another chamber. These things would at least be fast to check.
Best
Anders
- If you haven't done so already, try debugging with the "dummy cell" that is provided with the MultiClamp. If the dummy cell does not show this problem, there's likely an issue with your reference electrode.
- Which digitizer and recording software do you use? Some 3rd party software along with some digitizers can produce offset potentials even after they have been closed because they don't properly set their outputs to 0. Disconnect all front panel inputs to your MultiClamp to make sure this is not the case.
I agree with both Anders and Christoph - first thing would be to check with a cell model and if that behaves normally, then most probably you need to re-chloride either reference electrode (if you use silver pelet, you shoud clean the surface by gently scratching it) or the electrode inside the pipette or both. They should be dark grey and matt, as soon as they start to be a bit shiny, they need chloriding. Short circuit may also be the issue - it arises when a drop of liquid gets under the chamber, or when a drop of solution got there, water evaporated and conductive salts remained.
Hi guys, I updated the multiclamp software and it seemed to keep the holding voltage values on multiclamp from jumping. The pipette offset values seem correct (~ 40 mV) I also cleaned chamber and replaced both the pellet and the silver wire with newly chlorided ones. My pipettes look super clean and I could see internal solution flow out of them. However, the membrane test did not show any resistance value of the pipette whatsoever even in bath mode (no holding voltage).
When I use the model cell, the phenomenon is quite similar. Accurate value of pipette offset (~ -2.0 mV) but membrane test cannot read the resistance.
So I guess the problem is somewhere in the membrane test of clampex? Do you have any idea of how to fix this?
You mean when you apply test pulse you see straight line instead of rectangular pulse? That would mean your circuit is not closed - e.g., reference pipette is not pluged properly into the headstage.
I work with HEKA, so some things may be different. HEKA headstage has two plugs, so one can connect reference electrode (I mean grounding electrode) into a wrong one. It may be that a connecting wire is broken, but then you should not see the same straight line with a model cell.
Oh, mine actually has only one port to plug the grounding electrode in, so there is no room to do the wrong thing on this. You are absolutely right that I should not see the same straight line with the model cell if it were the broken connecting wire causing the problem. :( So bizarre...
Very rarely I too have experienced similar problems (pipette offset takes on unreasonable values when auto'd). In my experience what helps is to close the MultiClamp Commander program, cycle the MultiClamp power, and then restart the MCC program.
I had exactly the same glitch with my Multiclamp 700B, a wooping 1000 mV unfixable offset, the only thing that fixed it was reinstalling the console, after going hopelesly through all troubleshooting and then redaing this thread... I would hope Molecular devices make this more widely known...
I moved to a new lab and I have the same issue here with another Multiclamp 700B (I will try fixes again) basically I get a huge offset when switching from voltage clamp to current clamp, if you reset the console it goes back to voltage clamp without offset but the offset is back when you switch to current clamp. I want to have this fixed before I do a real experiment.
Hi Adrian
I am having same issue of huge offset while moving from VC to IC in Multiclamp 700B. This issue persists with model cell as well. How did you solve this in your new lab.
Thanks,@
Anurag
Hi Adrian,
I could sort out this issue. Was a problem with multiclamp commander. Hope Axon instruments have a look at it.
Thanks,
Anurag
I struggled with this problem for a while before realizing that I had a tiny and very slow leak between the cover glass and the plastic stage. When the leaked liquid eventually touched metal it would break the circuit. I only realized this was the issue because I found that I could dry out the stage (for around two hours) and restart an experiment and it would take an hour or so before the problem returned. I replaced the plastic stage and I have had no issues since.
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