Abstract
This chapter reviews the oxygen-18 in measurement of dopamine (DA) turnover in rat brain. Mass spectrometric evidence was obtained for the incorporation of at least one oxygen isotope in brain homovanillic acid (HVA) following in vivo exposure of rats to atmospheres highly enriched with oxygen-18. The high mass range in the mass spectra of the methyl ester heptafluorobutyryl derivative of authentic HVA and apparent HVA from brain extracts is demonstrated. HVA has the molecular ion at m/e 392 which is also the base peak. An abundant fragment is also present at m/e 333. An almost identical spectrum was obtained from brain extracts of animals exposed to a 16O2 containing atmosphere. On the other hand, in animals exposed to 18O2 gas, abundant. The atmospheric origin of the 180 atom incorporated was proved by injecting 18O labeled water into the animals which was not followed by incorporation of significant amounts of 18O in brain HVA. The usefulness of the technique for studies on brain DA turnover was demonstrated by studying the effect of chlorpromazine treatment on 18O, incorporation in brain HVA.
Published Version
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