Behavioural phenotype of APPC100.V717F transgenic mice over-expressing a mutant Aβ-bearing fragment is associated with reduced NMDA receptor density

The aim of this study was to characterize APPC100.V717F transgenic (TgC100.V717F) mice which over-express a mutant C100 fragment of the amyloid precursor protein. The mice were compared to TgC100 wild type mice (TgC100.WT) and non-transgenic controls at 4–9 and 16–22 months of age. TgC100.V717F mice showed behavioural hyperactivity, particularly at a younger age, as shown by increased numbers of elevated plus maze arm entries and Y-maze arm entries, enhanced baseline locomotor activity in the open field, and enhanced amphetamine-induced hyperlocomotion. This hyperactivity was less pronounced in TgC100.WT which only displayed significant differences to non-transgenic controls at a younger age for the number of Y-maze arm entries and baseline locomotor activity in the open field. In addition, TgC100.V717F mice, but not TgC100.WT, demonstrated cognitive deficits, as shown by reduced spontaneous alternation in the Y-maze and markedly reduced retention in a passive avoidance test. At an older age, TgC100.V717F mice showed enhanced startle and increased immobility time in the forced swim test. In the TgC100.V717F mice, but not TgC100.WT, the behavioural changes were paralleled by a significant reduction in the expression of hippocampal NMDA receptor subunits types 1 and 2A. Concomitantly, we detected axonal disruption and apoptosis in the hippocampus of TgC100.V717F mice. In conclusion, these data demonstrate that the mutant C100 fragment is an effector of biochemical and both cognitive and non-cognitive behaviours. These transgenic mice may be a model for the psychotic features associated with early Alzheimer's disease.