INVOLVEMENT OF DOMINANCE STATUS ON EMOTIONAL DEFICITS AND EXTRACELLULAR MATRIX DEGRADATION IN THE 3XTGAD MOUSE MODEL OF ALZHEIMER’S DISEASE

Dominance hierarchies are observed in laboratory mice, with an individual’s rank impacting cognitive performance and emotionality, and therefore suggesting they affect brain plasticity and adaptability. The extracellular matrix (ECM) is the structure surrounding cells in organs. In the brain, the ECM is involved in dynamic tissue remodeling via degradation enzymes such as matrix metalloproteinase-9 (MMP9). In this context, we investigated the relationship between an individual’s dominance rank, emotionality and MMP9 expression using a triple transgenic murine model (3xTgAD) of Alzheimer’s disease at an advanced stage of the pathology. The Tube Test (TT) served to expose the dominance hierarchic structures of groups and to identify dominant and subordinate individuals.Animals’ emotionality was evaluated using the Light/Dark Box (LDB) and the Splash Test (ST), and final scores were compared to a C57BL/6 control group. After tissue collection, hippocampal MMP9 expression was studied by Western Blotting (WB).3xTgAD mice behaved similarly to control animals in the ST, and the dominance rank did not affect self-grooming time. However, 3xTgAD mice showed a typical anxious-like behavior in the LDB, but their rank did not explain the time spent in the lit compartment.A lower hippocampal MMP9 expression was revealed in 3xTgAD mice compared to control animals, but no differences were found regarding their rank. Overall, we successfully exposed linear hierarchies of dominance in different mice groups using the TT. We revealed the emergence of anxious-like behavior and an altered hippocampal MMP9 expression in 3xTgAD mice, but without apparent connection to their individual’s hierarchical rank.