Current, voltage and bridge balance problems

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Dazed
Dazed's picture
Current, voltage and bridge balance problems

So I'm setting up my first rig for intracellular electrophysiology.

I'm using an Axoclamp 2B amplifier and pClamp 9 software, and I have calibrated the software to the Axoclamp. I haven't tried to impale anything yet. This problem starts when I simply place my electrode into the extracellular solution.

My problem is when I inject current down my electrode, the change in voltage occurs in the wrong direction. For example, if I inject a hyperpolarising step to remove series resistance the trace recording current moves in a negative direction but voltage appears to depolarise. Additionally, I cant use bridge balance to remove/calculate series resistance. Rather than reducing the step, it adds to it making it bigger!  Now I've checked my calibration for voltage, which I have done by changing the input offset. Voltage appears to have been calibrated properly as the values that appear on the axoclamp match those on the comptuer. When I use input offset to make the values more negative on the Axoclamp, they move in a negative direction on the trace too. Besides, the problems I'm having with bridge balance suggest it's something else.

I've remade my tip solution (1M KCl). I've used multiple tips. I don't have an oscilloscope or a model cell.

Any ideas please?

The FFM
The FFM's picture
Have you seen this help page?

Have you seen this help page?

http://mdc.custhelp.com/app/answers/detail/a_id/17410/~/how-to-use-the-axoclamp-2b-or-2a-for-whole-cell-patch-clamp-in-continuous

I would recommend obtaining a Patch1 U model cell.  It is essential to troubleshoot your setup.