Abstract # 1770 Social isolation and age have synergistic effects on brain hippocampal signalling pathways and memory

• Published in: Brain, behavior, and immunity Vol. 57; pp. e18 - e19
• Main Authors: Panossian, A, Flint, M.S, Patel, B.A, Yeoman, M.S
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.10.2016
• Subjects: Allergy and Immunology; Psychiatry
• ISSN: 0889-1591; 1090-2139
• DOI: 10.1016/j.bbi.2016.07.063

Social isolation (SI) is a major risk factor for morbidity and premature mortality in old age. Currently, the physiological and biochemical mechanisms that link SI with adverse health outcomes are unknown. This study examined how SI and age influence mouse memory (novel object recognition (NOR)), anxiety (open field test and elevated plus maze) and hippocampal serotonin (5-HT), 5,hydroxyindole acetic acid (5-HIAA) and norepinephrine (NE), transmitter systems which are important regulators of both behaviours. Male C57BL/6 mice aged 3 or 24 months were housed socially ( n = 3) or isolated for 2 weeks prior to experimentation. Following behavioural testing, mice were returned to their home cage for 24 hours and then sacrificed. The hippocampus was dissected for HPLC analysis of NE, 5-HT and 5-HIAA and serum isolated for corticosterone analyses. Age ( p < 0.01) and SI ( p < 0.05) both reduced performance in the NOR test (measured using a D-score). Hippocampal levels of NE were increased by age ( p < 0.01) and SI ( p < 0.05) as was 5-HT turnover, expressed as the ratio of 5-HIAA:5-HT (age; p < 0.001 and SI; p < 0.01). Significant negative correlations were observed between D-score and hippocampal NE levels ( p < 0.05) and the D-score and 5-HT turnover ( p < 0.001). Corticosterone levels and anxiety were unaffected by SI. This study demonstrates a synergistic effect of age and SI in regulating performance in the NOR test and hippocampal turnover of 5-HT and levels of NE.