Increased aggression in males in transgenic Tg2576 mouse model of Alzheimer's disease.

Behavioural and psychological signs and symptoms of dementia encompass a wide range of neuropsychiatric disturbances which coincide with progressing cognitive decline in Alzheimer's disease (AD). Physical aggression and agitation, which occurs in 20-65% of AD patients, is physically and emotionally stressful, not only to patients but also to immediate family and caregivers. The exact mechanisms underlying the increased aggressive behaviour in AD has yet to be elucidated. We used a transgenic mouse model, denoted Tg2576, which over-expresses a mutated human amyloid precursor protein (APP) gene implicated in familial AD, to investigate aggressive behaviour of males at the stage of amyloid beta pathology preceding overt amyloid plaque deposition in the brain. The aggressive behaviour of transgenic and non-transgenic littermate males was evaluated in a standard resident-intruder test in which an isolated resident male responded aggressively toward an experimentally naïve intruder male of A/J strain. We showed that 7-month-old Tg2576 resident males demonstrated significantly higher and unchanged level of aggression towards intruder males during 3 consecutive encounters as compared to their non-transgenic littermate counterparts. These results validate further the Tg2576 mouse model of AD underscoring its usefulness in studying non-mnemonic changes in behaviour related to the disease.