5-Methoxytryptamine in rat hypothalamus and human CSF. A fact or artifact?

Using thin-layer chromatography fluorometry, gas chromatography mass spectrometry and field ionization mass spectrometry the findings of Green et al. regarding the identification of 5-methoxytryptamine in rat hypothalamus could not be confirmed. On derivatization using pentafluoropropionic anhydride, melatonin underwent partial transacylation to yield 5-methoxytryptamine as one of the by-products. We thus consider the finding of 5-methoxytryptamine in rat hypothalamus by mass fragmentography as an artifact forming from melatonin, which is normally present in rat hypothalamus.