During phase III, the gait length coefficient of variability was increased ∼30% at 10 months of age, and the time allotted for braking in each stride was shortened by 40% and the paw angle was increased by 50% at 11 months of age of Shh-nLZC/C/Dat-Cre mice relative to controls ( Figure 4C and Supplemental Results D; see Table S1for all indices of gait analyzed). We then
tested whether drugs efficacious in the management of PD would modify the locomotion abnormalities of Shh-nLZC/C/Dat-Cre mice. We systemically injected L-DOPA (dopamine precursor) trihexylphenidate (THP) (muscarinic antagonist), or vehicle 30 min prior to the analysis of locomotion in 12-month-old Shh-nLZC/C/Dat-Cre and control mice. The increased Lumacaftor in vitro variability in stride length was normalized by L-DOPA and THP, brake stride ratios were normalized by THP but not L-DOPA, and alterations in paw angles were normalized by L-DOPA, but not THP ( Figure 4D). Taken together, our behavioral studies revealed a dynamic and progressive locomotion phenotype whose pharmacological responsiveness Rucaparib suggests underlying alterations in the functional balance
of dopaminergic and cholinergic neurotransmission. Similarly to BDNF, which supports survival of cortical-striatal neurons (Baquet et al., 2004), Shh can also be transported anterogradely through axons (Thérond, 2012). Because of the lack of evidence for an autocrine mechanism for Shh dependent support of DA neurons we therefore hypothesized that Shh signaling from dopaminergic projections to striatal targets might be of relevance to the maintenance of DA neurons. We found that ∼25% of all Ptc1+ cells in the striatum are neurons (Figures 5A–5C) and that 6% of all striatal neurons coexpress Ptc1 (Figure 5F). Conversely, 100% of all ACh neurons and 98% of all FS interneurons express Ptc1 (Figures 5D–5F), consistent with the relative prevalence of ACh and FS neurons among all striatal neuronal subtypes (Bolam et al., 2006). Hence, our expression data suggested that mesencephalic DA neurons could communicate by Shh signaling selectively with all ACh
and FS neurons, and nonneuronal cells among their projection targets in the adult striatum. In Shh-nLZC/C/Dat-Cre mice compared to controls at 6 months of age, we observed a reduction in the number of ChAT+ neurons in the striatum that over was most pronounced in lateral/anterior aspects of the dorsal striatum ( Figures 5G and S4A–S4C). ACh and FS interneurons make up together only ∼6% of total striatal neurons ( Figure 5F) and are locally projecting. These attributes make it impossible to distinguish neuronal loss from downregulation of phenotypic marker expression by the quantitation of the total number of neurons or the exploitation of specific projection patterns. However, the main striatal cell populations can be identified based on cell type specific perinuclear staining patterns that can be visualized by the DNA intercalating dye ToPro3 ( Figures S5A–S5C).