Dear Dinko,

You can try to obtain a decrease in the mEPSC amplitude by incubating you cultures with bicuculline for 48 hours.

Below you can find a fundamental paper talking about synaptic scaling:

Article Activity-dependent scaling of quantal amplitude in neocortical neurons

Thank you, that helped a lot!

I found a more recent one which doesn't use a pharmacological approach and focuses on single cell dynamics rather than whole network ones. Though it was very interesting

https://www.ncbi.nlm.nih.gov/pubmed/21040851

mEPSCs are chronically reduced in neuropsychological disorders, such as major depression. Please refer the following paper.