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Selected ion monitoring analysis of monoamine metabolites in cerebrospinal fluid. Application to the study of in vivo effects of α 2 ‐antagonists
Author(s) -
Dillen L.,
Duchateau A.,
De Potter W. P.,
Claeys M.
Publication year - 1987
Publication title -
biomedical and environmental mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0887-6134
DOI - 10.1002/bms.1200141119
Subject(s) - derivatization , chemistry , chromatography , acetic anhydride , extraction (chemistry) , homovanillic acid , biogenic amine , monoamine neurotransmitter , acetic acid , isotope dilution , amine gas treating , ethyl acetate , mass spectrometry , organic chemistry , serotonin , biochemistry , receptor , catalysis
The technique of isotope dilution mass spectrometry has been used for the measurement of biogenic amine metabolites in cerebrospinal fluid (CSF). CSF samples were collected from rabbits treated with α 2 ‐antagonists. The aim of our study was to determine the specificity of these drugs on the central nervous noradrenergic, dopaminergic and serotonergic activity as measured by the release of corresponding monoamine metabolites. 3‐Methoxy‐4‐hydroxyphenylethylene glycol (MHPG) and vanilmandelic acid (VMA) were used as parameters for the noradrenergic activity, whereas homovanillic acid (HVA) and 5‐hydroxyindole‐3‐acetic acid (5‐HIAA) were employed to follow the dopaminergic and serotonergic activity, respectively. For the measurement of the biogenic amine metabolites a published GCMS method has been adapted. Samples of 200 μl CSF were processed. Following addition of deuterated internal standards and acidification, extraction was carried out with ethyl acetate. Preliminary experiments with the analysis of MHPG using diethyl ether for extraction gave rise to emulsion formation and resulted in poor recoveries for MHPG and in irreproducibility problems due to a preferential extraction of non‐labelled MHPG, effects which were not observed with ethyl acetate extraction. Derivatization was done with a mixture of pentafluoropropionic anhydride/pentafluoropropanol (or hexafluoroisopropanol) in order to derivatize both hydroxyl and carboxylic acid groups. The derivatization procedure was optimized for the analysis of 5‐HIAA by carrying out a second reaction step with pentafluoropropionic anhydride alone in order to complete the derivatization for the indolic NH moiety. The molecular ions of the derivatized products were selected for detection. The methodology has been applied to evaluate the effects of two α 2 ‐antagonists, i.e. yohimbine and idazoxan. Yohimbine was found to increase the CSF levels of the noradrenergic metabolites MHPG and VMA and of the dopaminergic metabolite HVA and to have serotonergic effects, whereas idazoxan was shown to exhibit noradrenergic effect only.