Hippocampal slices for field recordings

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zazation's picture
Hippocampal slices for field recordings

I am trying to do some field recording in hippocampal slices but I have a problem.
I think that my slices for some reason are not healthy, because when I put the recording electrode in the stratum radiatum I first see a good fEPSP but it decreases until disappearing in a few minutes. I am using a vt1200 leica vibratome, and after decapitating the animal I put the brain in a becker with chilled modified acsf with sucrose. After doing the slices of 350uM thickness I put the slices in normal acsf at 30 degrees and I wait two hours of recovery before using it for the recordings.
Any suggestions for my problem???

c.hill's picture
How much stimulation are you

How much stimulation are you doing? Maybe you're stimulating too much and the cells around your stimulating location are getting fried.
Also, as you've not specifically stated this, are you perfusing your slices? If so, how fast/slow?

zazation's picture
 I'm using a  60usec

 I'm using a  60usec stimulation of 200uA to get the fEPSP and then I do an input output curve which starts from 0 to 1mA. I am perfusing the tissue at the rate of 1.5 ml/min.

Philly's picture

200 uA seems a little high (but not outrageous). you could try adjusting the location of your stimulation electrode to see if this can be reduced. 

it could be helpful if you describe the stim electrode, ie., bipolar, concentric, housed in glass pipette etc.

adjusting the speed and amplitude of the vt1200 can have a big influence on slice health. for me, less than 0.1mm/s and 1.5mm amplitude works well.

hrparra's picture
How frequent are you

How frequent are you stimulating, this can also a contribute to the running down of the response