Hi. Recently I've tried to record field potential in brain slice but failed. I use bipolar or monopolar stimulating electrode. Amp is Axopatch 1-D and headstage is CV-4. Recording was done at I-clamp mode. When the recording electrode containing normal ACSF touched the surface of brain slice, I started current injection but I could not see any responses but stimulus artifact. Would you please give me some advice?
As I had not recorded field potential before, I used brain stem slice (I have many experiences here). Age of mice is around P(postnatal day)3~P9. It is MNTB-LSO synapses at pons level.
Stimulating electrode(bipolar or unipolar) was located at MNTB and recording electrode (3~5 megaohm) was at LSO. The resistance of stimulating electrode was also in the same range of that of recording electrode (in case of unipolar electrode). I also tried bipolar electrode but failed.
LSO cells viewed with high magnification were alive and healthy. In voltage clamp mode, postsynaptic currents were elicited by stimulation at MNTB.
You need to tell us more. Where was your stimulating electrode? Where was your recording electrode? What was your stimulus parameters? How did you cut your brain slices? Are you certain your slices are alive? How did you confirm that? What was the resistance of your recording and stimulating electrode?
Hi Seungcheol Ahn,
Thanks for the update. That is a non-trivial slice, and one that I don't have personal experience with. My worry would be that you have cut the axons between the MNTB and the LSO.
If I were you, I would cut hippocampal slices. Pretty much any slice you cut that has a complete hippocampus in it will have a connection between CA3 and CA1. If you stimulate in stratum radiatum and put a recording electrode in the pyramidal cell layer you should see a large population spike (> 1mV). If you can not see this, then there is a problem with your stimulating or recording system.
However, if I had to make a guess, other than the worry that you have cut the MNTB LSO axons, it might be that the resistance of your stimulating electrode is too high. If we say that it has a resistance of 5MOhm, and you want to pass 100uA of stimulating current, then that would require 500 Volts, which is far more than any stimulating system that I know of has available. You'd be limited to less than 20 uA, which is starting to get pretty low (not that that amount can't work, it's just not what I would recommend for testing a system).
Try stimulating with a simple Tungsten wire (or something similar), with a resistance of 100kOhm or so.
Thanks a lot. I'll try and let you know. Today I
spent my time reducing the noise.
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