current at holding potential

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fai's picture
current at holding potential

when making giga seal (holding potential=0), the base line is at 0pA.
when Holding potential change from 0 to -80mV base line shift down. what type of this current? base line become so noisy. why? although there was no noise in the begning of giga seal at 0 holding potential
and when i cancle out offset current base line goes to 0 again.
I am also confusing about currrent at different holding potential, current is always 0 (base line at zero position) at any hoding potential.
For example when i hold membrane at 0mV and give the apply pulse form -60 to +60mV and 10mV steps, all the currents from -60 to -10mV gives inward while 10 to +60mV gives outward current. 0 mV gives 0 current.
In other case, when holding potential -40mV and apply same pulse all the currents from -60 to -50mV gives inward while -30 to +60mV gives outward current. -40mV gives 0 current.
what does it means and where the sodium and potassium current occur. if inward currrent is sodium and outward is potassium why it is change at different hoding potential while sodium current should be maximum near 0mV.