nal death that leads
to the cognitive decline.
"Estrogen replacement therapy might 'shore up' the synaptic connections
of neurons affected by the disease," said Einstein.
Earlier behavioral findings from Williams' lab had already shown that older
female rats' spatial memory is improved by estrogens administered in a cyclic
fashion. These findings led to the cellular studies in Einstein's lab that
now suggest a mechanism for this improvement in memory.
In the study, the team used aging female rats that had their ovaries removed
and, thus, were making no estrogen. The researchers divided the rats into
three treatment groups -- those receiving no estrogens, long-term chronic
estrogen doses, or a single acute dose of estrogen.
After the treatments, they performed microscopic studies that allowed them
to determine how the treatments affected neurons called granule cells in
the rats' hippocampus, a brain region involved in spatial memory. The scientists'
study of single neurons revealed that the rats exposed to acute estrogen
treatment had 40 percent more connective elements, called "dendritic
spines," on these neurons than did aged female rats with no estrogen
replacement or those exposed to long-term chronic estrogens. Dendritic spines
may be the basis for the brain's ability to develop new memories, the scientists
said.
"These studies suggest that the hippocampus of the female rat responds
best if it is exposed to estrogen in cyclical fashion, as is the case in
young adult female rats," Williams said in an interview. "Giving
aging females estrogen in a constant fashion was no better for their brain
than giving no estrogen at all.
"We're not yet sure whether this is also true in males, and one of
our next steps is to determine if neurons in aged males are responsive to
estrogens as well. They may or may not be since, paradoxically, males have
estrogens in their brains naturally throughout life, because testosterone
i
'"/>Contact: Dennis Meredith
meredithd@mail01.adm.duke.edu
919-681-8054
Duke University 20-Nov-1996Page: 1 2 3 Related biology news :1.
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