AMHERST, Mass. – Recent research shows that estrogens can no longer be thought of as exclusively reproductive hormones, but instead they are made in the brain and play a powerful role in cognition, learning and memory, says neuroscience researcher Luke Remage-Healey of the University of Massachusetts Amherst.
He presented recent findings on the role of estrogens as neuromodulators in a talk at Neuroscience 2013, the annual meeting of the Society for Neuroscience in San Diego on Nov. 10, and appeared on a panel with four other researchers to discuss “Sex Differences in Brain, Behavior and Health” at a press conference preceding the talk.
Remage-Healey and colleagues’ investigations supported by the NIH’s National Institute of Neurological Disorders and Stroke help explain why estrogens have been associated with improved cognition, learning and memory. New technology has been developed to study this in songbirds, which are particularly well suited to neurobiological and hormone experiments.
“While we might expect that estrogen levels are much higher in the female brain than in the male brain, in fact, estrogen levels are approximately equal in male and female brains at rest,” Remage-Healey points out. “What’s more, the levels are changing in the auditory cortex in response to stimuli in both sexes. These estrogens can have rapid actions on the neuron patterning in the sensory cortex and their ability to transmit information.”
He adds, “It’s the same molecule in birds, fish, dogs and humans, and the same molecule as is produced in the human ovary. When you get inside the brain, the old rules about estrogens being a ‘female hormone’ are tossed out the window. In fact, estrogens are synthesized by the brain itself, and our research shows that they can have rapid and local actions in males and females alike.”
The UMass Amherst research group’s findings show that neuroestrogens modulate information flow in the brain’s cortex within seconds to minutes, in contrast to the hours and days it takes for hormones circulating in the bloodstream to have an effect.
Using a microdialysis probe they developed for the finch experiments, the researchers can conduct real-time tests in the brains of active, alert zebra finches. The robust little birds are awake and flying, singing, eating and drinking with a tiny micron-diameter probe implanted in their forebrains. The probe not only allows researchers to measure estradiol levels but to couple those with recording electrodes that let them follow the activity of individual neurons.
The UMass Amherst neuroestrogen expert adds, “We’ve shown that estradiol changes in this same brain area when the animal hears a sound. This shows that it acts much faster and in a more specific way than we understood before. Estradiol could therefore target its activity to certain neurons synapse by synapse.”
Overall, the new findings could open the path to investigate more precisely the role of estrogens in learning, and perhaps reveal a way to deliver estradiol directly to neurons to enhance cognitive abilities without systemic side effects such as increased heart disease risk.