TH and Parkinson disease: In our extensive experience in modelling PD with 6-OHDA in rats, we find that intracerebral secretome elicits at least a two-fold increase in both measures of dopaminergic denervation (TH+ cell counts in the SNpc and fibers in the striatum) which historically correlates with functional improvements measured by skilled paw-reaching and rotarod tests [22,23,49,50].