increased holding current after drug

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Philly's picture
increased holding current after drug

I am recording from neurons before and after peptide application.

I have found that peptide application makes my holding current increase (become more negative) by roughly 15%. The change does not occur in the receptor KO ruling out deterioation in recording conditions.

I am using intracellular solution with High-Chloride and Cesium.

What are the possible reasons for seeing the increase in holding current??

BigPharmBoy's picture
By holding current, I'm

By holding current, I'm assuming you mean the current corresponding to the holding potential. I'm also assuming that the holding potential you chose remained constant before and after peptide delivery. The fact that the holding current is becoming more negative subsequent to peptide delivery suggests that there is compensation for an influx of positive charges coming into the cell.

It seems like you don't want to reveal too much about what you're doing, which is a sound strategy considering that you have come across a positive hit. Unfortunately though, we can't really know for sure what's happening. However, you did mention that there is a receptor to this peptide, so that helps a little bit.

Here are some possibilities that I can think of off the top of my head:
-The peptide may be activating a ligand-gated ion channel. Is that what the receptor is?

-The peptide may be activating a metabotropic receptor, which may subsequently result in opening of ion channels or release of intracellular calcium?
*The temporal aspects of this current might address the ion-channel vs metabotropic receptor question.
*Using a calcium chelator may address the release of intracellular calcium question.

-I know you said that you don't see the effect in the receptor knockouts, but just to be sure that the peptide isn't degrading the cell membrane, measure the membrane resistance before and after application.

Philly's picture
thanks for your reply and

thanks for your reply and valuable insights!

i particularly like your idea of checking whether there is release of intracellular calcium! this had not occured to me!