Isatin and tribulin concentrations are increased in rabbit brain but not liver following pentylenetetrazole administration

Isatin has recently been identified in rat tissues and normal human urine where it constitutes the major part of the endogenous monoamine oxidase inhibitor, tribulin. In this study, we have measured both isatin (by gas chromatography/mass spectrometry) and tribulin (inhibition of a standard rat liver monoamine oxidase preparation) in extracts of rabbit brains and livers after intravenous administration of the anxiogenic, proconvulsant agent pentylenetetrazole. There were increased levels of both isatin and tribulin in rabbit brains, but not in livers, after pentylenetetrazole, compared with saline treated controls. This finding supports the hypothesis that isatin is a component of tribulin activity and may have a role in anxiety or epilepsy.