[Neuroscience] Re: Ephys, Stimulation induces artifact but no response

jonesmat via neur-sci%40net.bio.net (by mathewjones from wisc.edu)
Fri Aug 5 13:49:05 EST 2011


On Jul 21, 11:30 am, Jun Wangxin <xinjunw... from gmail.com> wrote:
> Hi Guys,
>
> I have a prob and it'd be great if somebody could give me an idea how to
> solve it or just throw an idea!!
>
> So I've been doing voltage patch clamping, whole cell recording. I can
> record beautiful mIPSC/EPSC. Now I want to record evoked IPSC so I'm using a
> stimulator injecting current. I saw the artifact and it goes up and down to
> the intensity of my stimulation. I checked the connectivity of the system
> and it's all fine. I put the stimulator fairly close to my neuron and it
> should work. But I just can't see a response IPSC/EPSC. When I put only the
> stimulator, patch pipette and ground in the bath, I also only see the
> artifact, no current.  
>
> Anybody knows what's happening here possily, please?
>
> Thank you!
>
> Jun  
> --
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Another extremely naive question:
If you were recording mIPSC/mEPSCs, presumably you had TTX in your
extracellular solution. Did you make up a different solution for the
evoked responses that *doesn't* have TTX?

Besides that, this could be an electrical problem with your stimulator
connections. For example, if there was a broken connection to your
stimulating electrode, then it wouldn't pass any current at the tip of
the electrode, but you might still see an artifact because the
stimulator is still giving a big voltage pulse which could be picked
up at a distance by capacitively coupling to your recording electrode,
or even through the grounding connections on your rig. Try taking the
two wires off the stimulator box, and with the trode in the bath, use
a multimeter to check the resistance from one plug all the way to the
other plug (ie the resistance of the (+) wire to electrode tip to bath
to other electrode tip to (-) wire). Depending on the type of
electrode, this should be in the range of a few ohms to a few
kiliohms. If it's higher than that, there may be a broken or loose
connection.

Matt






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