AJP - Regulatory, Integrative and Comparative Physiology, Vol 265, Issue 5 1205-R1211, Copyright © 1993 by American Physiological Society
Modified microdialysis probe for sampling extracellular fluid and administering drugs in vivo
G. Yadid, K. Pacak, I. J. Kopin and D. S. Goldstein
Clinical Neuroscience Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
In vivo microdialysis provides an important new tool for investigating
changes in extracellular fluid levels of endogenous compounds in vivo.
Delivery of drugs via the microdialysis probe can be used to study local
release and metabolism of neurotransmitters, but the dialysis membrane
limits diffusion of substances between the perfusate and the extracellular
fluid. Thus there may be considerable delay in responses, drug
concentrations at the effector sites are less than those in the probe, and
high-molecular-weight substances cannot traverse the membrane at all. This
report describes a simple modification of commercially available
microdialysis probes. A cannula is glued to the external surface of the
probe. When glycine was administered via the cannula into the striatum of
conscious rats, increments in microdialysate concentrations of dopamine
were at least 10 times greater than when glycine was administered via the
dialysis fluid in the probe. The threshold glycine dose for behavioral
(turning) effects was also decreased by approximately 60-fold, and the time
to the peak neurochemical and behavioral effects was markedly decreased.
The modified probe did not destroy local catecholaminergic cells, as
indicated by tyrosine hydroxylase immunofluorescence. Use of the modified
microdialysis probe should facilitate pharmacological and neuroendocrine
studies in behaving animals.
