In American University’s Hall of Science, a neuroscience lab is working to understand the abilities of a particular hormone that helps with memory and healing.
In the lab, Professor Colin Saldanha and a team of students research the hormone estradiol by studying a type of songbird called a zebra finch.
Hormones coordinate processes in the body by binding to proteins on the surface of cells. The hormone then delivers a message to the cell, causing something to happen. Hormones are essential to many happenings in the body, including growth, blood sugar regulation, reproduction and sleep.
Estradiol is a type of estrogen hormone, made in both males and females. It’s usually talked about with the female reproductive system, but is also important to functions like mood balance, energy, weight regulation and more. Saldanha’s research focuses on the critical role that estradiol plays in memory and healing.
For example, when the brain is injured, cells close to the injury gain the ability to make estradiol. This prevents more cells from dying and helps to stop the injury from worsening.
“A cell type that normally doesn’t make estradiol switches on the ability to make it after the brain suffers an injury,” Saldanha said. “This happens in the birds I study, this happens in rats and it happens in humans.”
Estradiol is a hormone with a variety of abilities, able to affect many different processes in the body. Saldanha's lab is trying to understand how it can be used for a specific purpose, like healing, memory or mood regulation, without affecting a host of other processes at the same time.
“So in our lab, we try to answer, how is one hormone delivered to the right target at the right time at the right dose without affecting other target structures?” Saldanha said. “How do all these different things get controlled by one individual hormone without causing sort of cross-circuit meltdowns?”
To study these abilities and the mechanisms for how they work, the scientists focus on the zebra finch, specifically their hippocampus. This is a part of the brain that is key to memory and learning.
To test estradiol’s ability to help with memory, they prevented some of the zebra finches from making estradiol in the hippocampus. Then they compared the behaviors of these birds to the behavior of birds that were making the hormone.
The results showed that the finches not making estradiol in the hippocampus had issues with spatial memory, learning tasks and performing those tasks without making mistakes.
The team knows that estradiol helps learning and healing, and now they are trying to understand the mechanism for how it happens.
In response to a brain injury, they found that cells around the brain respond to the same chemical that your body creates as part of the innate immune response. This chemical triggers cells around the injury to start creating estradiol.
Understanding how estradiol helps with memory is a bit trickier. Estradiol is created in the synapses that link neurons in the brain. To figure out how cells use estradiol in the hippocampus requires a look at the genes within those cells.
The DNA inside every cell is a bit like a blueprint, or a plan that describes when cells should carry out certain actions, such as accepting hormones.
For this blueprint to be followed, certain parts of a DNA strand are copied. These copies take the form of a material called RNA. A team of three students in Saldanha’s lab examines RNA in zebra finch hippocampi to understand which patterns tell a cell to respond to estradiol.
“We know it affects memory,” Saldanha said. “We don’t really know how it works at the synapse.”
Zebra finches are used by the lab to study processes that also happen in the human brain, but looking at these birds in particular has another benefit. Songbirds have a fascinating ability: they can create new neurons in their brain throughout their adult life through a process called neurogenesis. This makes them good at healing their brain after an injury.
Adult neurogenesis in humans is still being researched, but various studies from the last decade suggest that humans and other mammals have a limited ability to produce new neurons late in life, especially compared to animals that evolved earlier, like fish or birds.
The brain’s ability to reorganize, restructure and strengthen itself in response to a change is called brain plasticity. Zebra finches have a higher brain plasticity than humans.
A brain with higher plasticity is easier to study because it allows scientists to better see the brain adapting to whatever factor is being studied in the experiment.
Discovering what enables the zebra finch brain to heal itself might be able to provide insight into how humans could recover from post-traumatic stress disorder, Alzheimer's disease or traumatic brain injury. This is one of the research goals, according to Saldanha.
“We have lost the ability to fix our brains,” Saldanha said. “And these guys do it, it’s just easy.”
This article was edited by Conor Gillingham, Marina Zaczkiewicz. Copy editing done by Sabine Kanter-Huchting, Ariana Kavoossi and Emma Brown.
