I'm patching granule cells in the olfactory bulb, but it's some days that I'm having troubles in getting seals. As soon as I approach the cell (but before seeing the "dimple" on the cell surface) the resistance jumps from 6/9MΩ to 15/30MΩ or even more! If I try to release the pressure/apply negative pressure the resistance doesn't change significantly. I thought about a leak in the tube connected to the pipette holder but this doesn't seem to be the case, I also tried to use the model cell but even in this case everything seems to work properly.