What hold and inject pressure to be used in microinjection?
It depends on volume that you want to inject and the width of your needle! Try to optimize the pressure by measuring the volume that you inject in mineral oil (I use grid in the objective to measure the drop size). You will decrease the volume by decreasing the injection pressure, of course. I work with zebrafish embryos so I am not sure if it is the same since it's in the water, but for DNA injection (1-2 nL) I normally use Hold Pressure 2 kPa and Injection Pressure 20-30 kPa.