The battery of tests for experimental behavioral phenotyping of aging animals

The purpose of the study was to develop a battery of tests to study social and cognitive impairments for behavioral phenotyping of aged experimental animals with physiological neurodegeneration. Male outbred CD1 mice used for the study were divided into two groups: group 1 consisted of 12-month-old male mice (physiological aging) and group 2 consisted of 2-month-old male mice (control group). A social recognition 5-trial test, elevated plus maze test (EPM), open field test, light-dark box test, and fear conditioning were used for estimation of the neurological state of experimental animals. We found that aged male mice exhibited lower interest in female mice in the social 5-trial task as compared to young male mice. Increased anxiety was observed in the group of aging mice in the EPM and light-dark box tests as compared to the control group. Lower locomotor activity and increased anxiety were found in the aging rats studied in the open field test. Physiological neurodegeneration was related to impaired associative learning and memory in the group of aging mice, which were observed in fear conditioning; particularly, consolidation of fear memory was dramatically suppressed. Analysis of behavioral factors, social interactions, and anxiety confirmed a model of agerelated neurodegeneration in the aged mice. We suggest that studies on animal behavior in the open field test, light-dark box test, and fear conditioning is the most informative approach for detection of neurological impairments, including deficits of social contacts and interaction, limitation of interests, and increased anxiety, in aging mice. This allows us to get new basic data on behavioral alterations in a model of age-related neurodegeneration and to develop novel therapeutic strategies for the treatment of age-related brain pathology.