HRH3 and Huntington disease: Since cognitive decline is observed in these HD mice from 6 mo of age (Brito et al., 2014; Giralt et al., 2012; Puigdellívol et al., 2015) and the D1R-H3R heteromers are expressed and functional until the age of 5 mo (Figure 4—figure supplement 1A,B), we chose 5mo-old animals to start the thioperamide treatment (Figure 4—figure supplement 2).