BUFFALO, N.Y. -- Experiencing chronic stress day after day can
produce wear and tear on the body physically and mentally, and can
have a detrimental effect on learning and emotion. However, acute
stress -- a short stressful incident -- may enhance learning and
Researchers at the University at Buffalo have shown, in trials
using rodents as an animal model, that acute stress can produce a
beneficial effect on learning and memory, through the effect of the
stress hormone corticosterone (cortisol in humans) on the brain's
prefrontal cortex, a key region that controls learning and
Specifically, they demonstrated that acute stress increases
transmission of the neurotransmitter glutamate and improves working
"Stress hormones have both protective and damaging effects on
the body," said Zhen Yan, professor of physiology and biophysics at
UB and senior author on the study. "This paper and others we have
in the pipeline explain why we need stress to perform better, but
don't want to be stressed out."
The study appeared July 20 in the online edition of
Proceedings of the National Academy of Sciences and will be
published in an upcoming print version of the journal. Eunice Y.
Yuen, Ph.D., UB research assistant professor of physiology and
biophysics, is the first author on the study.
To test the effect of acute stress on working memory, Yan, Yuen
and colleagues trained rats in a maze until they could complete it
correctly 60-70 percent of the time. When the rodents reached this
level of accuracy for two consecutive days, half were put through a
20-minute forced swim, which served as acute stress, and then were
put through the maze again.
Results showed that the stressed rats made significantly fewer
mistakes as they went through the maze both four hours after the
stressful experience and one day post-stress, compared to the
To determine if the corticosterone neuropathway was responsible
for the improved memory, as they proposed, researchers injected one
group of rats before the stressful forced-swim with a medicinal
compound that blocks the pathway, and injected another group with
saline. Results showed that the saline group, in which the
corticosterone neuropathway was not blocked, performed better in
the maze than the blocked group.
The researchers also determined that the stressful experience
did not increase depression or anxiety-related behavior in the
"It is known that stress has both positive and negative actions
in the brain, but the underlying mechanism is elusive," said Yan.
"Several key brain regions involved in cognition and emotions,
including the prefrontal cortex, have been identified as the
primary target of corticosteroid, the major stress hormone.
"Our current study identifies a novel mechanism that underlies
the impact of acute stress on working memory, a cognitive process
depending on glutamate receptor-mediated excitatory signals in
prefrontal cortex circuits."
The investigators have expanded this research in several
directions. In a paper currently under review, they have identified
the key signaling molecules that link acute stress to the
enhancement of glutamate receptors and working memory.
"In addition," noted Yan, "we have discovered that chronic
stress suppresses the transmission of glutamate in the prefrontal
cortex of male rodents, which is opposite to the facilitating
effect of acute stress, and that estrogen receptors in female
rodents make them more resilient to chronic stress than male
"All these studies should bring new insights into the complex
actions of stress in different circumstances that may be applicable
to humans in the future," she said.
Wenhua Liu, Ph.D., postdoctoral associate, and Jain Feng, Ph.D.,
associate professor, both in the UB Department of Physiology and
Biophysics, are co-authors on the study, along with Ilia N.
Karatsoreos, Ph.D., and Bruce S. McEwen, Ph.D., from The
The research was supported by grants from the National
Institutes of Health to Yan and a National Alliance for Research on
Schizophrenia and Depression Young Investigator Award to Yuen.
The University at Buffalo is a premier research-intensive
public university, a flagship institution in the State University
of New York system and its largest and most comprehensive campus.
UB's more than 28,000 students pursue their academic interests
through more than 300 undergraduate, graduate and professional
degree programs. Founded in 1846, the University at Buffalo is a
member of the Association of American Universities.