A research group led by the International Institute for Integrative Sleep Medicine, University of Tsukuba, discovered that orexin, a substance in the brain that controls sleep arousal and appetite, regulates "fearful levels."
When an animal feels fear, it unconsciously remembers the environment, surrounding objects, sounds, smells, etc. in relation to the fear.Then, if you fall into the same situation or feel the same sensation later, you will be frightened and changes in your behavior and autonomic nervous system will appear.This phenomenon is called "generalization", and post-traumatic stress disorder (PTSD) is a typical symptom.
Since orexin neurons are known to be excited in situations of fear or danger, the group focused on orexin and conducted research using genetically modified mice that can manipulate specific nerve cells at any time.As a result, it was found that orexin acts on a group of nerve cells existing in the locus coeruleus of the brain stem to control the level of fear.
Fear memory is stored in the amygdala located deep in the brain, but it has been clarified that orexin stimulates the outer part of the amygdala to revive (generalize) fear memory and strengthen the response to fear. rice field.It was also found that these fear responses were attenuated by blocking the binding of orexin to its receptors.
This result is epoch-making in that it clarified a new function of orexin involved in sleep-wake control and appetite.Orexin receptor antagonists have already been put to practical use as therapeutic agents for insomnia, but the new utility discovered this time needs further investigation.
Paper information:[Nature Communications] Orexin modulates behavioral fear expression through the locus coeruleus