I just started to learn how to do a patch clamp and had difficulties to obtain a gigaseal with ACSF 290 mmol/kg and Cs-based solution with osmolarity 310-317 mmol/kg.
When tried to do it after preparation of internal solution with the same recipe, just ~15 mOsm lower than ACSF, get gigaseal almost all the time without any problem. Although, I doubt that it's correct way to do it.
In some protocols people suggested to use osmolarity of external solution 300-310 with internal solution 285-290 mmol/kg, in some - with same osmolarity (not more than 5 mmol/kg difference).
While in Areles Molleman book there is information that it supposed to be easier to patch the cell with higher osmolarity of an internal solution.
Dear Nadezhda,
I fully endorse Max’s reply.
You can also check the morphology of your cells over time. If your cells are shrinking or swelling after obtaining a whole-cell configuration, I recommend to adjust your solutions to avoid this effect.
If your cells look healthy after 30 min or more, I would not worry too much about your osmolarity differences.
Good luck!
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