instabilityof access resistance

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braindrain
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instabilityof access resistance

Hi all,
I'm lately experiencing a frustrating problem when I do WC voltage clamp recording on midbrain dopaminergic cells. My access resitance is ok after rupture, but then it progressively increases over time, resulting in a dramatic voltage drop and in artifactual decay of the current I want to measure (Ih) with negative voltage steps. I have tried adding EGTA, (up to 1 mM ), KMetSulf, K gluc, no improvement.
This is driving me crazy, please help.