“…Since exposure to l-methyl-4-phenylpyridinium ion (MPP+), the bioactive metabolite of the parkin sonism-inducing agent l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP, 1) turned out to cause a selective reduction of complex I activity (Nicklas et al, 1985;Mizuno et al, 1987), compounds struc turally similar to 1, among them isoquinolines and ß-carbolines, have been investigated more closely Our special interest is focussed on 1-trichloromethyl-l,2,3,4-tetrahydro-ß-carboline (TaClo, 2) (see Fig. 1), a progressively-acting neurotoxin (for reviews see Sontag et al, 1996;Bringmann et al, 1998) that was recently found to be formed in trace amounts in humans after intake of the soporific agent, chlo ral hydrate . The distinct toxic potency of TaClo (2) towards dopaminergic (Grote et al, 1995;Rausch et al, 1995) and sero tonergic (Gerlach et al, 1998; Bringmann et al, 2000a) neurons appears to be strongly associated with its ability to severely disturb the neuronal energy metabolism.…”