I am doing an extracellular recording from a mouse retina. I use
planer metal electrodes on glass. However, the tissue when placed on
glass and perfused, starts to float in the medium, whatever small the
perfusion rate I keep. This is a big problem for me because for my
recordings, I need to have tissue sticking properly on the glass..

I have tried using a filter paper carrier, it still floats

Can someone help me in this regard?