In a combined PET study, reduced striatal expression of D1R, but not D2R was seen with D2R antagonist 3,5-dichloro-N-{[(2S)-1-ethylpyrrolidin-2-yl]methyl}-2-hydroxy-6-[11C]methoxybenzamide([11C]raclopride) and D1R antagonist (5R)-8-chloro-5-(2,3-dihydro-1-benzofuran-7-yl)-3-[11C]methyl-2,3,4,5-tetrahydro-1H-3-benzazepin-7-ol ([11C]NNC 756) in AD patients (Figure 9), compared to age-matched HCs (Kemppainen et al., 2000). This evidence concerns the gene DRD1 and Alzheimer disease.