TH and Parkinson disease: Nigral inoculation of brain homogenates in naive rats led to a decrease in the number of tyrosine hydroxylase (TH) positive neurons with the MSA and DLB groups having the highest proportion of neuronal loss (41 ± 5% and 49 ± 8% respectively) compared to the PD and CTR groups (27 ± 7% and 28 ± 4% respectively) at the final time point of 150 days (Fig. 6a).