Reduction in size of perforated postsynaptic densities in hippocampal axospinous synapses and age-related spatial learning impairments.
A central problem in the neurobiology of normal aging is why learning is preserved in some aged individuals yet impaired in others. To investigate this issue, we examined whether age-related deficits in spatial learning are associated with a reduction in postsynaptic density (PSD) area in hippocampal excitatory synapses (i.e., with a structural modification that is likely to have a deleterious effect on synaptic function). A hippocampus-dependent version of the Morris water maze task was used to separate Long-Evans male rats into young adult, aged learning-unimpaired, and equally aged learning-impaired groups. Axospinous synapses from the CA1 stratum radiatum were analyzed using systematic random sampling and serial section analyses. We report that aged learning-impaired rats exhibit a marked ( approximately 30%) and significant reduction in PSD area, whereas aged learning-unimpaired rats do not. The observed structural alteration involves a substantial proportion of perforated synapses but is not observed in nonperforated synapses. These findings support the notion that many hippocampal perforated synapses become less efficient in aged learning-impaired rats, which may contribute to cognitive decline during normal aging.
Nicholson
Daniel A
DA
Department of Cell and Molecular Biology, Feinberg School of Medicine and Institute of Neuroscience, Northwestern University, Chicago, Illinois 60611, USA.
Yoshida
Rie
R
Berry
Robert W
RW
Gallagher
Michela
M
Geinisman
Yuri
Y
D000375:Aging / Q000473:pathology*; D000818:Animals; D006624:Hippocampus / Q000473:pathology*; D007859:Learning Disabilities / Q000473:pathology*; D008297:Male; D018782:Maze Learning; D008569:Memory Disorders / Q000473:pathology*; D008854:Microscopy, Electron; D015388:Organelles / Q000648:ultrastructure; D051381:Rats; D020318:Rats, Long-Evans; D016037:Single-Blind Method; D013570:Synaptic Membranes / Q000648:ultrastructure*