STRIATAL DOPAMINE NERVE-TERMINAL MARKERS IN HUMAN, CHRONIC METHAMPHETAMINE USERS

Methamphetamine is a drug that is significantly abused worldwide. Alth ough long-lasting depletion of dopamine and other dopamine nerve termi nal markers has been reported in striatum of nonhuman primates receivi ng very high doses of the psychostimuiant(1-3), no information is avai lable for humans. We found reduced levels of three dopamine nerve term inal markers (dopamine, tyrosine hydroxylase and the dopamine transpor ter) in post-mortem striatum (nucleus accumbens, caudate, putamen) of chronic methamphetamine users. However, levels of DOPA decarboxylase a nd the vesicular monoamine transporter, known to be reduced in Parkins on's disease(4,5), were normal. This suggests that chronic exposure to methamphetamine does not cause permanent degeneration of striatal dop amine nerve terminals at the doses used by the young subjects in our s tudy. However, the dopamine reduction might explain some of the dyspho ric effects of the drug, whereas the decreased dopamine transporter co uld provide the basis for dose escalation occurring in some methamphet amine users.