In vivo on-line HPLC-microdialysis: simultaneous detection of monoamines and their metabolites in awake freely-moving rats

An on-line microbore high performance liquid chromatographic-electrochemica l (HPLC-EC) detection method has been developed for the simultaneous measur ement of dopamine (3,4-dihydroxyphenethylamine, DA), its metabolites 3,4-di hydroxyphenylacetic acid (DOPAC), and homovanillic acid (3-methoxy-4-hydrox yphenylacetic acid, HVA), as well as serotonin (5-hydroxytryptamine, 5-HT) and its metabolise 5-hydroxyindole-3-acetic acid (5-HIAA) in the striatum o f awake and freely moving rats. Our method was capable of detecting DOPAC, 5-HIAA, HVA, DA and 5-HT at retention time of 3, 5, 6.5, 9, and 24 min, res pectively, in repeated on-line microdialysis sampling. Analysis was perform ed using a 150 x 1 mm 5 mu m Cls microbore column attached directly to a th in-layer radial flow electrochemical cell (UniJet(R)) comprising a 6 mm gla ssy carbon working electrode. In order to accommodate signal outputs (due t o a varying level in the neurochemicals under investigation), an amperometr ic detector was equipped with a sensitivity programmable controlling softwa re for automatically switching sensitivity inattentively and repeatedly for each collection cycle. (C) 1999 Elsevier Science B.V. All rights reserved.