Singapore scientists have made a major breakthrough in understanding how anxiety is regulated in the vertebrate brain. The new findings have revealed the mechanism by which brain normally shuts off anxiety and established the relevance of zebra fish as a model for human psychiatric disorders.
The team of scientists, led by Suresh Jesuthasan from the Agency of Science, Technology and Research/Duke-NUS Neuroscience Research Partnership, showed that disrupting a specific set of neurons in the habenula prevents normal response to stressful situations.
In their experiments, Jesuthasan's team trained larval zebrafish to swim away from a light in order to avoid a mild electric shock. While normal fish easily learned this task, fish that had a specific set of neurons in the habenula damaged displayed signs of "helplessness".
Although they initially tried to avoid the shock, they soon gave up. What's more, these fish showed indications that they were more anxious than normal fish, such as being startled easily by non-harmful stimuli. Because of the similarity of the zebrafish brain to the mammalian brain, the study suggests that malfunction of the habenula is a possible cause of certain anxiety disorders in humans.
This means that it may be possible to use direct stimulation of the habenula as a way of treating some types of anxiety disorders in humans. The zebrafish model which the scientists developed in the course of their work may also be used in future drug discovery efforts for psychiatric medicines.
"Our work deals with fundamental aspects of human experience - stress and anxiety. We think that the habenula of the brain is associated with the assessment of whether a stress has been overcome. Our study provides one possible explanation as to why the need to control the environment is such a critical component of human behavior - the feeling of control enables organisms to deal with stress," said Jesuthasan.
The study was published in the journal Current Biology.