I’ve been having numerous issues with achieving stable baselines recording from the TA-CA1 synapse from juvenile (P12-P24) rat hippocampus slices. In addition, when applying drugs such as antagonists/inhibitors which should not show any effect on baseline, I have been seeing gradual increases in synaptic transmission that differ from what other students have previously shown in my lab.

I cull my rats by cervical dislocation and slice in ice cold sucrose aCSF and allow the slices to rest for 1 h at RT in regular aCSF. I then stimulate and record from the TA-CA1 and my first slice usually takes 2-3 hours to stabilise. I oxygenate my aCSF for at least 40 minutes prior to putting a slice on the rig and I use a platinum harp to hold it down in the bath. My rig uses a gravity feed system and the flow rate is 2.5 mL/min. My recording electrode is filled with aCSF and I bleach the silver wire every few days.

When the slice eventually stabilises for 20 min, I add my drug which has been oxygenating for at least 10 min. I can often see strange increases caused by the drugs that have not previously been seen. I thought it might be down to changes in oxygenation but I’ve been keeping all of my solutions in similar sized cylinders and have increased my oxygen so that everything is saturated.

Can anyone advise me how I can improve this and shed some light onto why I am seeing such instability and increases when switching drug?

Any help would be much appreciated, as I feel as though I’ve exhausted all ideas at this point.

Thank you!