Evidence has shown that ubiquitin proteasome system (UPS) impairment plays an important role in the dopamine (DA) neurodegeneration in Parkinson's disease (PD). It has been reported that application of proteasomal inhibitor lactacystin in ventral mesencephalon (VM) cultures can cause DA neurodegeneration, although the underlying mechanisms are not clear. Herein, we used the lactacystin-induced DA cell degeneration model to study the neuroprotection of glial cell-derived neurotrophic factor (GDNF) in VM cultures. We measured the expression of endoplasmic reticulum stress (ERS)-related genes, and determined the caspase-3 activation, apoptotic cell death, as well as alpha-synuclein-positive inclusions in DA neurons. We found that GDNF treatment significantly suppressed the expression of ERS-related genes and inhibited the activation of caspase-3 and apoptotic cell death without affecting alpha-synuclein-positive inclusions in DA neurons. Our study suggests that the protection of GDNF against DA neurodegeneration in the UPS impairment model is associated with ERS and caspase-3 suppression.