Animals

The AβPP_swe/PS1_dE9 (AβPP/PS1) founder mice were originally obtained from John Hopkins University, Baltimore, MD, USA (D. Borchelt and J. Jankowsky, Dept. of Pathology) ^{37, 38} and a colony was first established at the University of Kuopio, Finland and thereafter a colony was bred at the Central Animal Facility at Radboud university medical center, The Netherlands. In short, mice were created by co-injection of chimeric mouse/human AβPPswe (mouse AβPP695 harbouring a human Aβ domain and mutations K595N and M596L linked to Swedish familial AD pedigrees) and human PS1-dE9 (deletion of exon 9) vectors controlled by independent mouse prion protein promoter elements. The two transfected genes co-integrate and co-segregate as a single locus ³⁸. This line was originally maintained on a hybrid background by backcrossing to C3HeJ×C57BL/6J F1 mice (so-called pseudo F2 stage). For the present work, the breeder mice were backcrossed to C57BL/6J for fourteen generations to obtain mice for the current study. Before the actual experiments, animals were housed socially with a maximum of six animals per cage, with room temperature at 21°C, and artificial 12:12h light:dark cycle (lights on at 7 a.m.). Food and water were available ad libitum. The experiments were performed according to Dutch federal regulations for animal protection and were approved by the Veterinary Authority of Radboud university medical center, Nijmegen, The Netherlands, and the Animal Experiment Committee (called the Dierexperimentencommissie or DEC, RU-DEC 2011-058) of the Radboud university, Nijmegen, The Netherlands. The reporting of the animal experiments conforms with the ARRIVE guidelines ³⁹.

For the present experiment, we used a total of 17 16-month-old months old male mice (ten WT littermates, and seven AβPP/PS1 mice); at eighteen months of age, all animals completed the experiments and were euthanized. All behavioural and MRI experiments were performed in the Preclinical Imaging Centre (PRIME) of the Radboud university medical center between 8 a.m. and 6 p.m..