Apoptosis induced by an endogenous neurotoxin, N-methyl(R)salsolinol, is mediated by activation of caspase 3. An endogenous neurotoxin, N-methyl(R)salsolinol, has been proved to be involved in the pathogenesis of Parkinson's disease. Increased level of N-methyl(R)salsolinol in the cerebrospinal fluid and high activity of its synthesizing (R)salsolinol N-methyltransferase in lymphocytes were confirmed in the majority of parkinsonian patients. Recently this neurotoxin was found to induce apoptosis in human dopaminergic neuroblastoma SH-SY5Y cells. In this study, we tried to elucidate the intracellular mechanism of apoptosis induced by N-methyl(R)salsolinol, and proved activation of caspase 3 after incubation with this toxin by Western blot analysis. Further, a caspase 3 inhibitor, acetyl-L-aspartyl-L-glutamyl-L-valyl-L-aspartic aldehyde, prevented the nucleosomal DNA fragmentation completely. These results demonstrate that caspase 3 mediates apoptosis induced by an endogenous neurotoxin, N-methyl(R)salsolinol, which may cause apoptotic cell death of dopamine neurons in Parkinson's disease. Neurosci Lett 1999 Jun 4;267(3):153-6 Akao Y, Nakagawa Y, Maruyama W, Takahashi T, Naoi M Gifu International Institute of Biotechnology, Mitake, Japan. PMID: 10380999, UI: 99308706 http://www.ncbi.nlm.nih.gov/PubMed/ janet paterson 52 now / 41 dx / 37 onset snail-mail: PO Box 171 Almonte Ontario K0A 1A0 Canada website: a new voice <http://www.geocities.com/SoHo/Village/6263/> e-mail: <[log in to unmask]>