Studying Enzymatic Activities in

2 Measuring the Entire Time Course In a Single Experiment To 

4 Testing Drugs That Do Not Penetrate the Blood-Brain Barrier 

Microdialysis allows direct intracerebral administration of the drugs that normally do not cross the blood-brain barrier (BBB) or are metabolized in the circulation. It was demonstrated earlier (Ozaki et al., 1988 Westerink et al., 1990) that MPP+, a toxic metabolite of 1-methyl-4-phenyl-l, 2,3,6-tetrahydropyridine (MPTP), has a biphasic effect on TH activity when infused via the microdialysis probe for 20 minutes. Since, however, this drug does not penetrate the BBB, it was difficult to investigate its effects in vivo. Microdialysis overcomes this problem and has enabled the testing of a range of other modulators that previously could be studied only on in vitro preparations. 

The microdialysis technique can be used for continuous in vivo sampling of any body fluid. The main application field of microdialysis is for monitoring the intercellular chemical signaling and transport of molecules in the extracellular fluid. The principle of sampling, based entirely on dialysis (diffusion), ensures that no fluid is removed from or delivered into the sampling area. This principle, together with a fine diameter of the microdialysis cannula, makes it 

Anderson C, Andersson T, Wardell K (1994) Changes in skin circulation after insertion of a microdialysis probe visualized by laser doppler perfusion imaging. J Invest Dermatol 102 807-811. 

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