Researchers of a new study find what actually happens to the brain as a result of chronic social isolation. They also found a possible way of eliminating its negative effects, leading to potential applications in mental health disorder treatment and management.
Chronic Social Isolation
Researchers of a new study found that chronic social isolation actually affects the brain's chemistry and leads to negative behavioral changes. To test the effects of social isolation, researchers subjected mice to either two weeks or just 24 hours of social isolation and observed the resulting behaviors afterward.
Interestingly, researchers observed specific behavioral changes in the mice that have been socially isolated for longer periods, specifically in terms of fear and aggression. For instance, when faced with threat stimulus, the mice that were subjected to two weeks of social isolation remained frozen in place even after the threat is gone, while the mice that were subjected to 24 hours of social isolation stopped freezing once the threat had already passed.
Further, other observed behaviors among the mice subjected to chronic social isolation include persistent fear, hypersensitivity to threat stimuli, and increased aggression toward unfamiliar mice.
Brain Chemistry Change
A previous study found that tachykinin, a neurochemical, serves an important role in eliciting aggressive behaviors among socially isolated Drosophila flies. To understand the effects of tachykinin on social isolation-elicited aggression in mammals, researchers of the current study turned to looking at its effects on mice.
In mice, tachykinin's Tac2 gene encodes neurokinin B (NkB), which is a neuropeptide produced in regions of the brain such as the hypothalamus and amygdala, regions that are related to social and emotional behavior.
What researchers found was that chronic social isolation actually increased Tac2 expression, thereby also increasing the production of NkB in the brain. Further, when researchers artificially increased Tac2 levels in unstressed mice, they behaved just like the stressed, socially isolated animals.
Potential Treatment For Mental Disorders
Amazingly, the mice returned to normal behavior once researchers administered a drug that blocks the NkB-specific receptors. Further, they were able to see how Tac2 functions differently in different brain regions. Specifically, suppressing Tac2 in the amygdala removed the persistent fear but not the aggression, while suppressing Tac2 in the hypothalamus removed the aggression but not the persistent fear.
Researchers believe that this breakthrough could have potential implications in the treatment of mental illnesses in humans. So far, mental health treatments are often focused on neurotransmitter systems that circulate through the entire brain such as serotonin and dopamine, so messing with these could also cause certain unwanted side effects. With the current findings, treatments may become more specific and localized and possibly with lesser chances of side effects.
"Being able to precisely and locally modify a neuropeptide like Tac2 is a promising approach to mental health treatments," said study lead Moriel Zelikowsky.
The study is published in the journal Cell.