Another study by Selvaraj et al. (2009) showed that 1-methyl- 4-phenyl-1, 2,3,6-tetrahyrdro-pyridine (MPTP), a compound known to cause PD in mice by inducing mitochondrial dysfunction and neuronal apoptosis, reduces the expression of TRPC1 in the SNpc. This evidence concerns the gene TRPC1 and Parkinson disease.