TH and Parkinson disease: The aim of this study is to evaluate possible differences in the expression levels of apoptosis-related mRNAs (p53, Bax, Bcl-2, and caspase-3) activated by MPP+ using real-time quantitative RT-PCR analysis and evaluate the differential expression of a specific dopaminergic marker tyrosine hydroxylase (TH) in undifferentiated and RA-differentiated SH-SY5Y cells, for the assessment of suitable and accessible dopaminergic cell models for PD research.