Estrogen and Memory
Estrogen levels may play a role in learning and memory for older women. As this ScienCentral News video reports, scientists have learned that estrogen can affect brain disorders that come with old age.
The sex hormone estrogen plays a part in many brain processes, including memory. As women age, their bodies make estrogen. Neuroscientists are studying just what effect this has on the brain.
“When there’s more estrogen,” explains Teresa Milner, professor of neuroscience at Weill Cornell Medical College, “the nerve cells can form more connections between each other and make the memories stronger. Then, the better you’re able to learn certain things.” Nerve cells in the brain form connections when their branches, called dendrites, sprout twig-like protrusions called spines.
Writing in the March 15, 2003 issue of the journal Neuroscience, Milner and her team explained how they used a powerful electron microscope to study nerve cells associated with learning and memory in female rats. They found that as estrogen levels increase in the female rats during their estrous cycle, there is an increase in the formation of new spines.
“This increase in spines is correlated with increased learning and memory,” says Keith Akama, a post-doctoral fellow at Rockefeller University’s Neuro-Endocrinology department, who collaborated with Milner.
“Estrogen increases the number of these spines along these branches, and this is very good for the nerve cells. Because the more spines you have on the branches, the more likely that you’ll have a higher number of connections from one nerve cell to another, and the more connections you have from nerve cell to nerve cell, which are called synapses. The more synapses you have, the better the brain functions.”
Akama found that estrogen stimulates the activity of a particular enzyme that leads to the formation of the spines. Milner’s research revealed that estrogen acts not only at the cell’s nucleus, which was previously known, but also directly at the receptors on the spines, which leads to faster connections.
As women get older, their estrogen levels go down, which means fewer spines, and a less sharp memory. Researchers hope that this new understanding of how estrogen acts in the brain could help them to design safer drugs to target only the positive effects of estrogen in the aging brain. It could also help them design better protocols for estrogen replacement therapy, and even help to delay the onset of Alzheimer’s disease.
In the meantime, they suggest keeping the mind active; doctors often recommend that older people do crossword puzzles as a “brain workout.” “If you can use what little [estrogen] you have, even to strengthen your synapses, then even what’s left will become stronger,” says Milner. “If you don’t use it, then these synapses get lazy and they just don’t put out as much and eventually, there’s nothing. There’s no message coming through.”
The research is funded by the National Institutes of Health and the Ares-Serono Foundation.