Chronic stress may lead to memory problems by interfering with glutamate signaling in the prefrontal cortex, according to a study in mice.
Young male rats exposed to repeated stress had significant memory impairment and suppression of glutamate transmission in that brain region, Zhen Yan, PhD, of the State University of New York at Buffalo, and colleagues reported in Neuron.
The findings suggest that the prefrontal cortex “is a more sensitive area in response to repeated stress, especially during the adolescent period when this region is still undergoing significant development,” the researchers wrote.
Chronic stress can impair executive functions, such as memory and attention, and has been shown to trigger maladaptive changes associated with stress-related mental disorders. The major stress hormone cortisol, for instance, has been linked with depression.
Some work has shown that stress hormones impair behaviors mediated by the prefrontal cortex, the brain region responsible for executive function.
Yet the underlying mechanisms remain elusive, the researchers said.
To delve deeper into those potential mechanisms, Yan and colleagues looked at glutamate receptor-mediated synaptic transmission, which has been suggested to be crucial for working memory, in mice.
Why Future Holds More Stress
The bad news is that real-time is not going away. We are not going to settle for less than right now. This means that the future holds more and more stress. As we evolve into a society that demands more information and more information processing immediately, we are also evolving into a society of people under constant stress. The fact that computers are ubiquitous is making it all that much worse. Of course people were stressed last century as well, but in the seventies when you went home for the weekend you, relaxed. Nowadays? No way. There is no 30 minute period in my life that I do not check email. Going off the grid is really hard for many of us. Real-time is not only stressful, it is addictive.
Faster causes stress. So does the non-stop flow of information. When we are unable to fall asleep at night, we lie down stressed and thinking why? Why am I doing all of this? The tough part is that there is no other way. We do not know how to do what we do and not be stressed. So for better or worse, we are rushing forward through the sea of information towards more stress.
They found that repeatedly exposing juvenile male rats to stress significantly impaired the temporal order recognition memory, a cognitive process controlled by the prefrontal cortex (P<0.01).
Stress situation that occur in daily life may cause people to feel irritated, threatened or anxious – a set of emotions that are collectively referred to as stress. Many people become stressed when they are involved in conflicts, worried about problems or pressed for time. The body interprets these pressures as a threat to life. In response, the pituitary gland signals the adrenal glands to release adrenaline, noradrenaline and cortisol – hormones that prepare the body to fight or flee. As a result, muscles
tense, alertness increases and heartbeat, respiration and blood pressure escalate. Though these effects enable the body to react quickly when faced with true danger, a body in a constant state of stress begins to lose its capacity for defense. Lack of sleep and exposure to excessive noise make coping with stress more difficult. Overtime, illness (including heart disease and cancer) and mental burnout may result. Fortunately, relaxation methods, herbal remedies and water therapies can help reduce many types of stress.
What you can do:
Relaxation is the antithesis of stress. It is therefore essential for people susceptible to stress to relax and avoid
being constantly “on ” due to the increase secretion of stress hormones. Besides using naturopathic therapies, try to make time in
your day to “Switch off,” doze and dream.Exercise is also very helpful in alleviating the effects of stress.
At the same time, they found that glutamatergic transmission in pyramidal neurons in the prefrontal cortex was significantly suppressed in those rats, although there was no loss of synaptic connections, they said.
Different downstream mechanisms have been identified in the effect of stress on glutamatergic signaling. Chronic stress reduces the expression of several receptors and proteins involved in glutamate transmission, including GluR1 and NR1 subunits (GluR1: 45% to 51% decrease, NR1: 55% to 63% decrease, P<0.01). Chronic stress also reduced functional AMPAR and NMDAR current densities in prefrontal cortext neurons: AMPAR: 81.9 picoamperes/picofarad (pA/pF) for control versus 42.9 pA/pF for stressed (P<0.01) NMDAR: control: 93.3 pA/pF for control versus 40.4 pA/pF for stressed (P<0.01) Yan and colleagues also found that blocking certain molecular processes prevented the loss of glutamatergic responses and recognition memory in the stressed mice. "Our results suggest that repeated stress dampens prefrontal cortex glutamatergic transmission by facilitating glutamate receptor turnover, which causes the detrimental effect on ... cognitive processes," they wrote. The findings may also help explain why stress responses can act as a trigger for many mental illnesses, they added. "Since prefontal cortex dysfunction has been implicated in various stress-related mental disorders, delineating molecular mechanisms by which stress affects [this brain region] should be critical for understanding the role of stress in influencing the disease process," Yan said in a statement.
The researchers reported no conflicts of interest.
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Primary source: Neuron
Source reference: Yuen EY, et al “Repeated stress causes cognitive impairment by suppressing glutamate receptor expression and function in prefrontal cortex” Neuron 2012; DOI: 10.1016/j.neuron.2011.12.033.