The halogenated tetrahydro-beta-carboline "TaClo": a progressively-acting neurotoxin.

"TaClo", (1-trichloromethyl-1,2,3,4-tetrahydro-beta-carboline) which is structurally very similar to MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), increases the sensitivity to apomorphine in aging rats after subchronic daily application (0.2 mg/kg i.p.) for 7 weeks. Nine weeks after the last treatment with TaClo, the running speed of the animals during spontaneous nocturnal activity was significantly diminished, and 9 months after the last injection rats developed a pronounced hypersensitivity to apomorphine (0.4 mg/kg s.c.). TaClo, which can be readily produced from endogenous tryptamine and the non-natural aldehyde chloral, appears to be a drug that is able to induce a slowly-developing neurodegenerative process.