A previous PET imaging study aiming to investigate CB1 receptors in APP/PS1-21 AD mice showed significantly lower binding ratios of [18F]FMPEP-d2 in certain brain regions of 9- and 15-mo APP/PS1-21 mice, matching the results of our study; however, no differences in CB1 protein levels between any of the groups were detected 9. This evidence concerns the gene CNR1 and Alzheimer disease.