Abstract
β-Carbolines occur in man and rat. The concentration in various tissues is about 100
to 1000 times lower than that of classical neurotransmitters. Administration of β-carbolines
in animals induces overlapping but not identical activity profiles. The molecular
modes of action differ. For example, harman (1-methyl-β-carboline) acts as an endogenous
inhibitor of monoamine oxidase [E.C. 1.4.3.4.], subtype A, whereas norharman (β-carboline)
probably acts by stimulation of a specific β-carboline receptor which is different
from the benzodiazepine-GABA receptor complex. There is substantial evidence that
tetrahydroisoquinolines occur under physiological conditions as well. Whether tetrahydropapaveroline
serves as a precursor of morphinanes in mammals, as has been found in opium poppies,
remains to be elucidated.
Key words
β-Carbolines - mammalian alkaloids - morphinanes - salsolinol - tetrahydroisoqui nolines
- tetrahydropapaveroline
