Hi Thomas and Segundo!
I've only done extracellular recording for a couple of days in a sommer
course two years back, but I just grabbed my old notebook and found some
of the information you guys are looking for. Maybe it turns out to be a
of help for you:
> > 1. What properties should the electrode have (compared to a
> > conventional patch electrode e.g. resistance, shape, filling etc.)?
We used glass pipettes filled with 2M NaCl. With this solution the
pipettes we used averaged around 10MOhms.
> > 2. Do I have to use a different headstage?
>> I don't think so. There're headstages specific for extracellular
> recordings, but I think those used in patch-clamp could work.
As far as I remember we used the same headstage for patching and for
> > 3. Can I use my usual patch amplifier (Axoclamp 2B)?
We used an Axoclamp 2B. As far as I understand that's acutally an
overkill. I'm know of one lab that uses self-built amplifieres for
recording extracellular signals in cerebellar slices. For those of us
who are less inclined to build one, there are fairly simple
field-potential amps to be had for relatively little money (the EXT
module series from www.npielectronic.com for example).
> > 5. Where to place the electrode (deep in the tissue or superficial)?
THAT is the big question. It depends on what you want to see. The idea
of current sinks and current sources is very central to understanding
the whole concept of extracellular recording. There is a well written
and informative chapter on this stuff to be found in:
"Foundations of Cellular Neurophysiology" (Bradford Books (Hardcover))
by Daniel Johnston and Samuel Maio-Sin Wu
A personally believe that to be a very good starting point. Maybe some
of the more experienced electrophysiologists in this group have some
more to say on this.