Cognitive and emotional alterations in young Alzheimer's disease (3xTgAD) mice: effects of neonatal handling stimulation and sexual dimorphism.

Alzheimer disease is the most common neurodegenerative disorder and cause of senile dementia. It is characterized by an accelerated memory loss, and alterations of mood, reason, judgment and language. The main neuropathological hallmarks of the disorder are β-amyloid (βA) plaques and neurofibrillary Tau tangles. The triple transgenic 3xTgAD mouse model develops βA and Tau pathologies in a progressive manner which mimicks the pattern that takes place in the human brain with AD, and showing cognitive alterations characteristic of the disease. The present study intended to examine whether 3xTgAD mice of both sexes present cognitive, emotional and other behavioral alterations at the early age of 4 months, an age in which only some intraneuronal amyloid accumulation is found. Neonatal handling (H) is an early-life treatment known to produce profound and long-lasting behavioral and neurobiological effects in rodents, as well as improvements in cognitive functions. Therefore, we also aimed at evaluating the effects of H on the behavioral/cognitive profile of 4-month-old male and female 3xTgAD mice. The results indicate that, (1) 3xTgAD mice present spatial learning/memory deficits and emotional alterations already at the early age of 4 months, (2) there exists sexual dimorphism effects on several behavioral variables at this age, (3) neonatal handling exerts a preventive effect on some cognitive (spatial learning) and emotional alterations appearing in 3xTgAD mice already at early ages, and 4) H treatment appears to produce stronger positive effects in females than in males in several spatial learning measures and in the open field test.