Hi Luca,

The problem with your fEPSPs might have several reasons:

What kind of microtome are you using? Is it a generally preferred one? To my experience, different brands make a considerable quality difference.

Make sure that the z vibration is as small as possible. Vertical pressure during the cutting is really bad for slices.

Cutting angel is related with the blade you are using. Make sure that the cutting angel is slightly greater than (or at least equal to) the half of the blade angel. The tip of the blade is V shaped in high magnification. Your cutting line should be the lowest line in the tissue (lower than the blade body).

Relating to the stimulation electrode:  Glass electrodes are used to induce LTP. But what is the resistance of your stimulation electrode. If it is too high (like same as patch electrode) it is possible that you may be stimulating a very small area and that stimulation is simply not enough to induce LTP. You can try to lower the resistance of your glass stimulation electrode (you can try 1 Mohm for start). Or you can use bipolar stimulation electrodes.

Good luck.

Hi Ismail,

thanks so much for your answer. i use a Leica VT1000S for my preparations and as blade i use commercial shave blades (wilkinson for istance), and i'm cutting with 15 degrees of blade inclination, i think that all the other things are ok. For this that concerne the stimulation electrode i tried to use electrodes with different resistance but with no good news. I'll try the bipolar electrode maybe.

Thanks so much and have a nice day

Luca

Hi, when you said you want to cut "coronal" hippocampal slices, I assumed you meant the  dorsal (the upper part)  hippocampus. Usually, a normal coronal cut will do (that means cutting is perpendicular to the mid-line). Since you are not getting good fEPSP responses, you may want to tilt 10 degrees along the perpendicular line.

As to the stimulating electrode, a glass pipette (similar to a mono-polar electrode) is not a good idea. I think it is not the resistance issue, but that a mono-polar stimulating electrode is affecting too many fibers bundles (work out   the source-sink  circuit for mono-polar electrode yourself). Most people use bipolar stimulating electrode, which will only stimulate smaller range of fibers. A better one is a concentric type, commercially available. But you can also make one yourself, by twisting two insulated wires together, and remove the insulator at the tips