Aim: To analyze the relationship between proteasome inhibitor (lactacystin) and the degeneration and death of dopaminergic neurons, so as to develop a new therapeutic strategy for Parkinson disease. Methods: The study was carried out in the Chinese National Human Genome Center (Beijing) between March and November 2005. The human neuroblastoma cell line SH-SY5Y was offered by Beijing Institute of Neuroscience. SH-SY5Y cells treated with 50 μmol/L 6-hydroxydopamine (6-OHDA) were used as a cell model of Parkinson disease. The cells were plated to culture dishes, 6-well plate and 96-well plate in the logarithm growth period, and treated with different administrations after 24 hours: control group, 6-OHDA 50 μmol/L group, 6-OHDA 50 μmol/ L + lactacystin 0.1 μmol/L group, 6-OHDA 50 μmol/L + lactacystin 0.25 μmol/L group, 6-OHDA 50 μmol/L + lactacystin 0.5 μmol/L group. Cell survival rate =number of live cells/number of live cells in the control group×100%. The absorbance (A)value was detected with ELISA microplate reader, the wave length was 540 nm. A value= A of cell well in the experimental group-A of blankwell. The mean of 8-well reading of each group was used to assay. Cell viability = A of experimental well/A of parallel control well×100%. Results: 1 In SRB assay, 50 μmol/L 6-OHD A was toxic to cells, the cell survival rate was only (51.31±3.52)% as compared with that in the control group, and it increased to (72.16±3.97)%, (82.36±3.78)% and (91.44±3.06)% after 0.1, 0.25 and 0.5 μmol/L lactacystin were added, and there were significant difference, among the groups (P < 0.05). But the treatment of 0.5 μmol/L lactacystin only had no obviously influence on the cell survival rate. 2 In cell count, 50 μmol/L 6-OHDA was toxic to cells, which was manifested by the reduce of cell number, the cell survival rate was only (47.33±3.25)% as compared with that in the control group, and it increased to (69.67±2.13)%, (80.38±1.12)%, (90.59±2.01)% after 0.1, 0.25 and 0.5 μmol/L lactacystin were added, and there were significant differences among the groups (P < 0.05). But the treatment of 0.5 μmol/L lactacystin only had no obviously influence on the cell survival rate. 3 The normally cultured neurons had great density, clear outline, obvious process, and good reflectivity of cell body. Most of the neurons treated by 6-OHDA died, the process of remain cells were shortened or diminished, the cell body shrunk, outline was not clear, and the reflectivity of cell body was bad. The density and form of the cells treated by 6-OHDA and lactacystin ranged between them. Conclusion: Proteasome inhibitor is protective to dopaminergic neuron through blocking apoptosis, but the definite mechanism needs further study.