In addition, we also measured the levels of PPP1R1B/DARPP-32 (protein phosphatase 1 regulatory inhibitor subunit 1B), a component of the dopamine signaling pathway used as an indicator of pathological progression in HD [30,31], and found a reduction in PPP1R1B levels only in AAV-mHTT-injected mice using WB after 3 weeks but not after 10 d post-injection (Figure 1H). Here, PPP1R1B is linked to Huntington disease.