I've been trying to get mGluR-dependent LTD (field recording) in hippocampus of juvenile mice using S-3,5-DHPG. I have noticed that experiments always work best right after I make the stock solution for DHPG. I wonder if it is possible that due to the high purity, the drug is so sensitive to light and oxygen that its potency decreases drastically over even just 3-4 days.
For today, my LTD got back to baseline after DHPG application in a wildtype p16 animal. It worries me a lot. Upon drug application, the field got depressed acutely ( to around 50%), but even before I switched back to ringer, the field gradually grew back up. Could anyone think of any reasons why this could be happening? I think slices are probably healthy ( baseline was very stable and field looked nice) and ringer is made on the day of the experiment. I would really appreciate it if anyone could point out the possible mistakes that I've been making so that I can rectify it.