Hippocampal neuron and synaptophysin-positive bouton number in aging C57BL/6 mice

• Published in: Neurobiology of aging Vol. 19; no. 6; pp. 599 - 606
• Main Authors: Calhoun, Michael E, Kurth, Daniel, Phinney, Amie L, Long, Jeffrey M, Hengemihle, John, Mouton, Peter R, Ingram, Donald K, Jucker, Mathias
• Format: Journal Article
• Language: English
• Published: London Elsevier Inc 01.11.1998; Elsevier Science
• Subjects: Aging; Aging - physiology; Animals; Behavior; Biological and medical sciences; Brain; CNS; Cognition - physiology; Development. Senescence. Regeneration. Transplantation; Fundamental and applied biological sciences. Psychology; Hippocampus; Hippocampus - cytology; Hippocampus - physiology; Immunohistochemistry; Male; Maze learning; Memory; Mice; Mice, Inbred C57BL; Mouse; Neurons; Neurons - cytology; Neurons - physiology; Stereology; Synapses; Synapses - physiology; Synaptophysin; Synaptophysin - metabolism; Task Performance and Analysis; Vertebrates: nervous system and sense organs; Brain; Synaptophysin; Mouse; Neurons; Memory; Aging; CNS; Stereology; Behavior; Hippocampus; Synapses; Maze learning; Vertebrata; Synaptic button; Senescence; Mammalia; Rodentia; Central nervous system; Age; Brain (vertebrata)
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/S0197-4580(98)00098-0

A loss of hippocampal neurons and synapses had been considered a hallmark of normal aging and, furthermore, to be a substrate of age-related learning and memory deficits. Recent stereological studies in humans have shown that only a relatively minor neuron loss occurs with aging and that this loss is restricted to specific brain regions, including hippocampal subregions. Here, we investigate these age-related changes in C57BL/6J mice, one of the most commonly used laboratory mouse strains. Twenty-five mice (groups at 2, 14, and 28–31 months of age) were assessed for Morris water-maze performance, and modern stereological techniques were used to estimate total neuron and synaptophysin-positive bouton number in hippocampal subregions at the light microscopic level. Results revealed that performance in the water maze was largely maintained with aging. No age-related decline was observed in number of dentate gyrus granule cells or CA1 pyramidal cells. In addition, no age-related change in number of synaptophysin-positive boutons was observed in the molecular layer of the dentate gyrus or CA1 region of hippocampus. We observed a significant correlation between dentate gyrus synaptophysin-positive bouton number and water-maze performance. These results demonstrate that C57BL/6J mice do not exhibit major age-related deficits in spatial learning or hippocampal structure, providing a baseline for further study of mouse brain aging.