The hippocampus, a medial temporal lobe
structure necessary for the formation of spatial memory, is
particularly affected by both normal and pathologic aging.
In previous studies, we observed a significant age-related
increase in dopaminergic neuron loss in the hypothalamus
and the substantia nigra of female rats, which becomes
more conspicuous at extreme ages. Here, we extend our
studies by assessing spatial memory in 4–6 month-old
(young), 26-month-old (old) and 29–32-month-old (senile)
Sprague–Dawley female rats as well as the age-related
histopathological changes in their dorsal hippocampus.
Age changes in spatial memory performance were assessed
with a modified version of the Barnes maze test. We
employed two probe trials (PTs), one and five days after
training, respectively, in order to evaluate learning ability
as well as short-term and longer-term spatial memory retention.
A set of relevant hippocampal cell markers was also
quantitated in the animals by means of an unbiased stereological
approach. The results revealed that old rats perform
better than senile rats in acquisition trials and young rats
perform better than both aging groups. However, during
short-term PT both aging groups showed a preserved spatial
memory while in longer-term PT, spatial memory showed
deterioration in both aged groups. Morphological analysis
showed a marked decrease (94–97%) in doublecortin neuron
number in the dentate gyrus in both aged groups and a
reduction in glial fibrillary acidic protein-positive cell number
in the stratum radiatum of aging rats. Astroglial process
length and branching complexity decreased in aged rats. We
conclude that while target-seeking activity and learning ability
decrease in aged females, spatial memory only declines
in the longer-term tests. The reduction in neuroblast number
and astroglial arborescence complexity in the dorsal hippocampus are likely to play a role in the cognitive deficits of aging rats
The hippocampus, a medial temporal lobe
structure necessary for the formation of spatial memory, is
particularly affected by both normal and pathologic aging.
In previous studies, we observed a significant age-related
increase in dopaminergic neuron loss in the hypothalamus
and the substantia nigra of female rats, which becomes
more conspicuous at extreme ages. Here, we extend our
studies by assessing spatial memory in 4–6 month-old
(young), 26-month-old (old) and 29–32-month-old (senile)
Sprague–Dawley female rats as well as the age-related
histopathological changes in their dorsal hippocampus.
Age changes in spatial memory performance were assessed
with a modified version of the Barnes maze test. We
employed two probe trials (PTs), one and five days after
training, respectively, in order to evaluate learning ability
as well as short-term and longer-term spatial memory retention.
A set of relevant hippocampal cell markers was also
quantitated in the animals by means of an unbiased stereological
approach. The results revealed that old rats perform
better than senile rats in acquisition trials and young rats
perform better than both aging groups. However, during
short-term PT both aging groups showed a preserved spatial
memory while in longer-term PT, spatial memory showed
deterioration in both aged groups. Morphological analysis
showed a marked decrease (94–97%) in doublecortin neuron
number in the dentate gyrus in both aged groups and a
reduction in glial fibrillary acidic protein-positive cell number
in the stratum radiatum of aging rats. Astroglial process
length and branching complexity decreased in aged rats. We
conclude that while target-seeking activity and learning ability
decrease in aged females, spatial memory only declines
in the longer-term tests. The reduction in neuroblast number
and astroglial arborescence complexity in the dorsal hippocampus are likely to play a role in the cognitive deficits of aging rats
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