DRD1 and Parkinson disease: Some neurotoxin-induced and genetic rodent models of PD are known to reproduce the dendritic degeneration of SPNs, but the reduction of the total dendritic length is not as dramatic as in human patients at the terminal stages of PD (e.g., 6-hydroxydopamine (6-OHDA) model in Fieblinger et al., 2014, 2018; aphakia model in Alberquilla, Gonzales-Granillo, Martín, & Moratalla, 2020; knockout D1R mice [D1R−/−] in Suarez, Solis, Sanz-Magro, Alberquilla, & Moratalla, 2020).