Multiclamp 700B in a current clamp mode is suitable for fEPSP recordings. You problem is probably related to the positioning of the electrodes or orientation of the blade during the slicing.

Thank you for this response. Next time I will make a figure to demonstrate my electrodes placement.

Include your voltage clamp data when you report back, including showing you can evoke an EPSC.

Anton is definitely correct, you can record beautiful LFPs with the 700B in current clamp I=0 mode. However, I have a suspicion. It sounds like you are used to doing whole cell recordings, presumably under DIC optics. This means you might have a nice full bath... covering the slice by 3mm or even more. Try reducing the height of the bath so that it is barely covering the surface of the slice.. just the thinest film over the slice. Remember, LFPs are generated by extracellular current flow, and the higher the resistance to extracellular current flow, the bigger the LFP. Big paths mean low resistance current paths. To be honest, I'm not completely convinced that is the true reason why LFPs are bigger in shallow baths, but I am certain that a shallower bath makes for better LFPs. Old school people liked working in interface chambers for a reason.

Thank you William, you are correct. I was doing a lot of whole cell experiments in the slices and cultures, but I had never done any extracellular field recordings. I will definetely try your advise and report here.

You definitely can! How thick are your slices? I found that 400 um coronal slices are better for fields. Also your perfusion system must be very stable. In my experience you don’t see fEPSP’s when the slice quality is poor! Try to perfuse your animal with chilled choline chloride solution before removing the brain and cut your slices in the same solution, then transfer them to the recover ACSF bath at 32-36 C for at least one hour. Then switch off the bath temperature and keep your slices at RT. You can then use them for many hours.I use normal patch pipettes (3-5 MOhms) filled with ACSF.

Dear all.This is an interesting question (and timely for me too) that I like to explore further if you don't mind. I want to get back to fEPSPs recordings in my old lab where we had a beautiful (& functional) setup using Axon 200B amplifier and 1440A digidata. I said we had because when I came back, that setup does no longer exist. I now have the Axon 700B amplifier and I am trying to do what Gleb is doing to no avail too. I happened to be told exacly like Gleb that we need to have a pre-Amp. (someting like the P55 A.C. Pre-Amp. from Grass). The signal output from the Pre-Amp. would then be used instead of the 700B signal output (this signal goes to one of the 1440A Analog input and then use pClamp as usual to monitor it).

Going to William's great (and really valuable! Thanks William) insight(s), one need to be able first to generate evoked-EPSCs (or EPSPs) in the CA1 region and I have to admit that I have a big problem evoking responses 100% of the time. I get beautiful patch seals, nice clean whole-cell breaking but get only about 1 in 5 evoked responses when I try to evoke EPSCs. Is it a stimulation positioning problem? or someting else?. I have done ePSCs (EPSPs) and fEPSPs in the past, I never experienced anything like this. I would love if someone could comment further on this question of how to position the stim or any other relevant tricks to improve the evoking responses. Many thanks in advance!

Thank you all for your inputs. I am glad to hear that I am not alone with such problem, and we can discuss different approaches/solutions to fix it. I will post future updates after I'll do experiments next week. Someone told me that I need to brake the tip of the patch pipette to be able to record fEPSPs. I did this, and no result. I could not evoke any responses, so I had used very high stimulus to elicit the response as demonstrated on the attached figures. The pipette was 300kOm and parallel stimulation electrode from WPI was 0.5 mOm for each wire. I understand that slice on the image looks bad. I demonstrate it to you to get an advise on electrode placement next week. Again, thank you in advance for your help.

I agree with Paula; optimization of the conditions (temperature, oxygenation, slicing) may be required. Use regular patch pipettes (3-5 MOhm) resistance. Try horizontal slices, they may work better for you. You are recording the stimulation artifact so the amplifier is OK. You can use any AC-coupled differential amplifier instead of Multiclamp 700 but it does not really matter. Grass P511, WPI DAM50 or even home-made amplifier will do. Multiclamp in current clamp mode is basically a DC amplifier and it is even better then these AC-coupled amplifiers since it will less distort the signal by the high pass filter. Many papers were written with Multiclamp 700; using it for the fEPSP recordings is somewhat overkill but it is an excellent measuring instrument.

Hi Gleb,

Sorry to hear you're having so much trouble with this. You DEFINITELY (and I very rarely say things with such certainty) do NOT need to break the tip of your electrode to record fEPSP. 1-3Meg electrode will let you record fEPSPs with no trouble.

We need to get you seeing a clear response before we work on perfecting things, but in the fullness of time, once you can see a nice EPSP when you're intracellular (to confirm that your slice anatomy is okay), and then get an fEPSP you really shouldn't need your recording and stimulating electrodes so close. Get that stimulating electrode at the CA1/CA3 boundary. But as I say, you need to get a better response first.

The thing I find curious is that there is no clear fiber volley. Perhaps it is hidden by the stimulus artifact, but even in basically dead slices I would expect that.

Hi Gleb,

I hope you've sorted out your problem,

I'm facing the exact same problem and while my research in the web I ran into your question,

I realize it has been a while since you did your experiments but I'll be very grateful if you can share with me your insights.

for me, it seems that although every technical parameter looks fine I can`t get any evoked response, but I do see the artifact as you mentioned.

I had the same problem and I resolved it. My problem was a simple confusion about where to stimulate and where to record. the 700B is suitable to record beautiful evoked-fPSPs (1 to 2 mV and sometimes more). I use mice hippocampi. I record a clear fiber volley followed by the fPSP. I use Platinum-Iridium electrodes (50 K) from Microprobes. They work beautifully and seem to last and resist better to everyday use than tungsten ones. My pipette is 4-5 MOhms filled with aCSF. Good luck Samma. If you need more info, contact me directly. Fouad

Fouad Lemtiri-Chlieh thank you for your input.

I`m contacting you directly for more clarification.