DRD1 and Huntington disease: In a preclinical Huntington’s disease (HD) mice model (HdhQ7/Q111 knock-in), D1R-H3R heteromers were detected by PLA in the striatum, cerebral cortex, and hippocampus slices at 2–4 months of age but were undetectable at early disease states at 6–8 months of age [129].