Their report appears this week in the journal Behavioral Neurosciences.
The researchers made the discovery when studying the effects of estradiol on activities mediated by the prefrontal cortex, a brain region that is vital to working memory and to the ability to plan, respond to changing conditions and moderate or control one’s behavior.
Working memory is the ability to briefly remember information needed for a particular task, said Susan Schantz, a U. of I. professor of veterinary biosciences and principal investigator on the study. An example in humans is a phone number that is forgotten soon after the number is dialed.
“With working memory you’re just keeping it active until you use it,” she said.
In the new study, rats were trained to press one of two levers to obtain a food reward. Those that alternated between the levers (which were withdrawn from the rat enclosure for a few seconds between trials) received a reward. Those that hit the same lever twice in a row got no reward. Rats exposed to estradiol performed worse than their counterparts on this task, earning significantly fewer rewards.
A second set of tests measured the rats’ ability to wait before responding to a stimulus. The rats had to wait 15 seconds before pushing a lever to get a reward. Those exposed to estradiol performed worse on this task than those that were not exposed.
“That’s the test where we really saw the most striking effects with estradiol,” Schantz said. The estradiol-treated rats “were not as good at waiting,” she said.
“Rats treated with estradiol are definitely a lot more active and make a lot more lever presses,” said neuroscience graduate student Victor Wang, the lead author on the study. “That’s not conducive toward being rewarded.”
The researchers had not expected to see such pronounced results. In fact, the study had been designed to give them baseline information for a separate inquiry into the effects of soybean estrogens on cognitive function. They planned to compare the effects of chronic estradiol exposure to the effects of chronic exposure to genistein, a phytoestrogen found in soybeans. Genistein is believed to have similar effects in the body as natural or synthetic estrogens, although no study has definitively proven that it does.
Schantz and her colleagues had focused on the prefrontal cortex because it is rich in estrogen receptor beta (ER-beta), a protein that spurs gene expression and other activities in the cell when it binds to estradiol. Genistein also activates ER-beta.
Some women take genistein supplements or eat soy-based foods to reduce hot flashes or other symptoms of menopause, Schantz said.
“Women take them thinking they’ll be a safe alternative to hormone-replacement therapy and they might help hot flashes,” she said. Those who have heard that hormone replacement can improve cardiac or brain function also hope that eating soy or taking genistein supplements will have the same effects, she said.The effects of hormone replacement therapy (HRT) are more complex – and problematic – than once thought. A recent large-scale study of HRT in post-menopausal women was stopped because of an increased risk of stroke and blood clots in women taking estrogen alone, and a higher than average incidence of breast cancer, cardiovascular disease, blood clots and stroke in women taking estrogen and progesterone.
Performance in these tasks involves brain structures outside the prefrontal cortex.
The research indicates that multiple factors influence the effects of estradiol on the brain, Schantz said. The timing of the exposure, the types of brain functions or structures studied and the age of the test subjects can all generate different results, she said.
Diana Yates | University of Illinois
For a chimpanzee, one good turn deserves another
27.06.2017 | Max-Planck-Institut für Mathematik in den Naturwissenschaften (MPIMIS)
New method to rapidly map the 'social networks' of proteins
27.06.2017 | Salk Institute
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
28.06.2017 | Earth Sciences
28.06.2017 | Physics and Astronomy
27.06.2017 | Power and Electrical Engineering