During one patch the membrane resistence should be over 1GO, and when open the cell to get the wholle cell, should this resistence decreased?
Once you rapture the patch membrane (whole cell), the circuit resisitance is the sum of series resistance and the membrane resistance. Thus, I believe the resistance will be smaller than that measued in on-cell mode (G seal).
Actually in my case,
in on-cell mode: a few or some G ohms
in whole cell mode: from several hundreds M ohms to a few G ohms.
...well, I patch neurons, and after open the cell, the resistence keep over one GOm, most of the time about three to four GOm, and the R-series decreased to about 20 to 40MO, and I get good currents. The point is that someone ask me why the membrane resistence keep so higt after open the cell, by the contrary it should decreased a lot, so I don´t know why and now I´m confused about that...
As my opinion, your value of R-series seems to be too big. After the suitable Rs compensation, the voltage error would be some to several mV (if you measure a current amplitude >1 nA). This might give an impact to the current shape.
If I were you, I would calibrate the machine first, make the new solution, use a bigger size of the electrode (2 - 3 MO), and chek if the same thing happens or not. If the same happened, then this can be the reality in your experimental condition.
How about your base line at your holding potential? Such a high value, it must be close to zero. Does your pipette solution have KCl or CsCl?
Finally, do you use hematclit tube for the electrode? I have used it and the similar experience.
...I don´t use hematclit tube; I think is becuse this experimental conditons. The zero line is ok, no so far from zero. The cell firing fine in Current clamp mode. Is only that I have not clear if there is normal that the membrane resistence keep over GOm even the cell is open and give good currents.