TH and Parkinson disease: As in post mortem specimens from human PD patients, a significant reduction in the number of tyrosine hydroxylase (TH) positive neurons was observed in the substantia nigra (SN) (p < 0.05) (Fig. 2a, d) and significant reduction in DAB striatum intensity was observed (p < 0.05) (Fig. 2b, d) in rotenone-treated rats at 60 days.