Fig. 1: Evaluation of motor behaviour and dopaminergic integrity during the premotor stage of the animal model of progressive parkinsonism.

A Schematic representation of the viral vector inoculation site (red asterisks, bilaterally in the SN_pc) and the experimental design indicating the evaluated post-inoculation (p.i.) time points. B Schematic representation of the dopaminergic projections from the SN_pc to the striatum in the rat brain (left). The ventrolateral region of the SN_pc projects to dorsal areas of the striatum (motor striatum), mainly to the dorsolateral striatum (DLS), while caudomedial SN_pc neurons project to the ventral and medial parts of the striatum (associative and limbic striatum). Representative photomicrographs of TH⁺ staining in coronal sections of the SN_pc and the striatum from animals that received EVV or hα-syn inoculation assessed at 4 w p.i. Scale bars: 300 µm (nigral sections) and 100 µm (striatal sections) showing pathological TH⁺ terminal swellings and thickening of fibres at 4 w p.i. in the striatum of the hα-syn group. Representative photomicrographs of DAT staining in coronal sections of the SN_pc and the striatum from animals that received EVV or hα-syn inoculation assessed at 4 w p.i. Scale bars: 100 µm. C Number of TH⁺ neurons in the SN_pc normalised to the corresponding EVV group. D Relative optical density (ROD) analysis of TH expression in the dorsolateral striatum normalised to the corresponding EVV group. E Number of swollen TH⁺ axons in the dorsolateral striatum of hα-syn and EVV groups. Values are presented as the mean ± SEM (n = 7–9 for each group and time point; Two-way ANOVA followed by Sidak post-hoc test: *P < 0.05, **** P < 0.0001). F Open field test for evaluating locomotor activity before surgery (baseline) and at 1, 2 and 4 w p.i. in EVV and hα-syn inoculated animals. Box plots showing the distance (cm) and % of the time moving (n = 7–9 for each group and time point; Two-way ANOVA for repeated measures: no statistical differences). Abbreviations: a.u., arbitrary units; DLS, dorsolateral striatum; DMS, dorsomedial striatum; NAc, nucleus accumbens; VS, ventral striatum; VTA, ventral tegmental area. G Relative optical density (ROD) analysis of DAT expression in the dorsolateral striatum normalised to the corresponding EVV group.