Field potential recording from Hippocampal Slices

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sharmakaushikp's picture
Field potential recording from Hippocampal Slices

I am trying to record fEPSP's from rodent hippocampal slices (animals of 6-8 week of age). The slices are recovered in an interface-type recovery chamber for atleast 2 hours before being used for recording purposes. The flow rate of oxygenated solution into the chamber is maintained at 2-3 ml/min. A bipolar tungsten stimulation electrode and a 2.6-3.8 Mohm resistance 3M NaCl filled glass recording microelectrode is being used. I stimulate the Schaffer Collateral pathway and record from CA1 stratum radiatum. I am using a constant current stimulus isolator, and normally I require about 40-50 uA current to get an appropriate (40% of maximal fEPSP) response slope value.
With different tetanization protocols (single tetanic train, or 4 tetanic trains), the extent of the LTP that I get is as follows:
            Post-tetanic potentiation= about 60-70%
            LTP=20-25% atleast stable for 2 hours or more
However, the extent of LTP reported in papers is much higher than what I am getting now. The slices look healthy and give good results when used for any molecular/ pharmacological treatment.
Considering the above mentioned conditions, what are the different measures that can be taken to get a higher LTP induced in my experiments, or atleast something comparable to those reported in the literature.
Where are the possibilities of me missing out some important facts or errors that can lead to lower values of LTP induced in my system. Kidly suggest me the changes that  I can do, or errors that I can rectify. It seems to be a problem with LTP induction and not in LTP maintainance. If this is true, what can be the specific problem in this case?

sas418's picture
 I don't really do LTP

 I don't really do LTP studies, but I know that most slice studies are done in much younger animals (at least this is true of rats -- somewhere between P8-P20 is the norm).
From what I hear, you get much better results from younger animals, and the recordings are much easier to do ...

Penning's picture
Regarding with field

Regarding with field potential recording, do you use single-ended or differential amplifier? and how large your noise level is?
It seems that differential amplifier would eliminate the power-line noise,
but the signal I got is contrary to this popular belief. 
The power-line noise I got is around 100uV(peak to peak)by using a single-ended amplifier
but it increase to 200uV by using a differential amplifier.