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Microdialysis (was: Maesurement of Neurotransmitter

Ewan ecm5f at faraday.clas.Virginia.EDU
Fri Apr 19 07:48:09 EST 1996

rgazzara at nctr.fda.gov  writes:
> I wouldn't recommend constructing your own probes as this is difficult
> and time consuming at best.  You are much better off purchasing probes
> from commercial sources.  This is much more expensive, but you save
> time (and grief).  If you are careful and store the probes properly,
> you can reuse them 5 times or more.  I've reused CMA probes for up to
> 25 times. 

25? Wow.  Lab record so far is 18 :)  But I agree that buying
probes is the way to go - BAS have an interesting new line, but
last I looked they were more expensive than CMA.

> As for measurement, it depends on what you are interested in.  The
> monoamines (dopamine, norepinephrine and serotonin) and their
> metabolites can be quantified best by HPLC with electrochemical
> detection (HPLC-EC).  Acetylcholine can also be quantified by HPLC-EC,
> but the limit of detection is lower with GC-MS.  The amino acids are
> usually quantified by HPLC.  Other compounds are quantified by a
> variety of analytical tools, such as HPLC with UV detection, etc.

We use HPLC for both monoamines and ACh.  I would add, though,
that when I started using microdialysis for glucose
measurements I strove *hard* to avoid using the HPLC method for
assay; fluorometry, IMHO, gives good sensitivity down to the
nanomole range if there is a suitable enzymic assay available
while avoiding the *Major* hassles that can accumulate with
changing HPLC IMERs, analytical columns, pump rods, fixing
leaks... this may be an aberrant experience, but the HPLC for
small-volume neurochemical measurements is a sometimes
necessary evil in my eyes rather than a desirable method.

Have fun :)

Ewan McNay - ewan at virginia.edu / (804) 296-2089 or 982-4753 (lab)
Gamer/socialist/neuroscientist/cook (not necessarily in that order)
	"Outside of a dog, a book is a man's best friend.
	 Inside a dog, it's too dark to read."	- G. Marx

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