It is well known that emotions such as anxiety contribute to insomnia.However, the neuroscientific mechanism behind it has been unknown.
Research groups such as the University of Tsukuba have now revealed through a series of experiments using mice that neurons in the brain region involved in fear and anxiety cause arousal due to anxiety.
The stria terminalis nucleus, which is a part of the limbic system and controls emotions such as fear and anxiety.The research group analyzed the role of GABAergic neurons (neurons that use GABA as a neurotransmitter) localized in the stria terminalis nucleus in controlling arousal.As a result, it was found that when GABAergic neurons were specifically excited, mice that had non-rem sleep were immediately awakened.It was also found that continuous excitement of the same neuron prolongs arousal time and reduces both non-REM sleep and REM sleep.
We also investigated the involvement of orexin, a substance in the brain that controls arousal, in this action.Then, it was found that orexin is not involved in the wakefulness of the former, while the orexin-based action is mediated in the latter.
This study reveals a part of the mechanism by which GABAergic neurons induce arousal. GABA was said to have anxiolytic and hypnotic effects, but this experiment showed that it was rather involved in arousal.In addition, while orexin receptor antagonists that have been put into practical use as insomnia treatment agents have the effect of improving insomnia caused by persistent anxiety, they are immediately awakened by emotions, for example, when danger occurs at bedtime. It was confirmed that it did not affect arousal.
These results are considered to be important findings for the development of new therapeutic agents for anxiety disorders and insomnia.
