HRH3 and Huntington disease: To test whether D1R-H3R heteromers can indeed be targets for treating HD, we investigated their expression and function in the striatum, cerebral cortex and hippocampus of a widely accepted preclinical model of HD, the heterozygous HdhQ7/Q111 mutant knock-in mice, and their wild-type HdhQ7/Q7 littermates (Giralt et al., 2012; Puigdellívol et al., 2015).