There was a nearly 70% reduction in tyrosine hydroxylase (TH, the rate limiting enzyme in the synthesis of dopamine and was used as a marker of the dopaminergic neurons) immunostaining, which was used to identify dopaminergic neurons in the SN, on the 6-OHDA-injected side of PD mouse brains (6-OHDA vs control: p = 0.0003) compared with control mouse brains, whereas OCN treatment significantly prevented the reduction in dopaminergic neurons in PD mice (6-OHDA vs 6-OHDA+ 4 μg/kg OCN: p = 0.0175) (Fig. 1c). The gene discussed is TH; the disease is Parkinson disease.