Continuous Monitoring Access Resistance

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yv86's picture
Continuous Monitoring Access Resistance

 Hi all,

Most if not all of the whole cell papers mention in their methods section that "access resistance was contiuously monitored" , whether the method used is  voltage clamp or current clamp. I do whole cell recordings using current clamp (using Clampex and Multi Clamp 700 B). Can someone please explain how Ra can be continuously monitored in current clamp? Is it by periodically checking the value of Bridge Balance?

Thanks very much.

azylbetal's picture
One of the methods is giving

One of the methods is giving a short current step at the beginning of each trial. The time course of the membrane potential change elicited by the current injection is the sum of two exponential functions: the charging of the membrane (with time constant Rm*Cm) and the charging of the electrode (with a time constant of (Ra*C-electrode). You can fit the data to this sum and get Ra (or rather, the difference between Ra and your bridge balance value, or 0 if your bridge balance is set correctly and there were no changes in Ra). In a way, that's like checking the value of the bridge balance (only automatically).