Many studies have highlighted the negative health effects of stress, but a recent study sheds light on how chronic stress changes neuronal structure and function in the brain. Researchers from Nanchang University examined brain structure changes and published their findings in Stress and Brain. Neuronal structural changes are associated with anxiety disorders and other neuropsychiatric illnesses, so this study can inform effective therapies for those impacted by prolonged stress.
Previous studies have shown that chronic stress causes the loss of glutamate receptors that contributes to mental illness. The hippocampus activates the sympathetic nervous system, which causes the norepinephrine to be released into multiple organs. As study author Dr. Jun-Yu Zhang explained, “Considering the critical role of glucocorticoids — a stress hormone — in the modulation of brain structure and function by stress, we hypothesized that the glucocorticoid receptor may be a potential mediator of the differential regulation of neurons by chronic stress.” By understanding the mechanisms of glutamate receptors, researchers can develop therapies targeting specific signaling pathways for patients managing chronic stress.
The researchers exposed four groups of mice to various durations of restraint stress. Over ten days, the mice were put into a tube fitted to their bodies for different time intervals: two hours one time, two hours on three days, two hours every day, or not at all. The researchers examined how the levels of corticosterone (glucocorticoid in mice) and the expression of the glucocorticoid receptors changed throughout the interval. They found that stress hormone levels in the mice increased with restraint time, and they increased remarkably in the mice stressed every day. They also found that chronic stress did not affect the number of neurons expressing glucocorticoid receptors but that it did appear to significantly increase the intensity of expression only for neurons projecting into the hippocampus. The study showed that the neurons integrated into different neural circuits triggered different stress reactions despite the same microenvironment. This finding suggested that circuit selectivity might be involved in the process of chronic stress-induced excessive anxiety.
The University research team’s future research will explore the glucocorticoid receptor mechanism by examining the effects of chronic stress when the receptor is blocked or removed.
Sources:Eureka News Alert, Stress and Brain