Hippocampal neuron and synaptophysin-positive bouton number in aging C57BL/6 mice.
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.
Calhoun
M E
ME
Neuropathology, Institute of Pathology, University of Basel, Switzerland.
Kurth
D
D
Phinney
A L
AL
Long
J M
JM
Hengemihle
J
J
Mouton
P R
PR
Ingram
D K
DK
Jucker
M
M
D000375:Aging / Q000502:physiology*; D000818:Animals; D003071:Cognition / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology* / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D016708:Synaptophysin / Q000378:metabolism; D013647:Task Performance and Analysis
D016708:Synaptophysin