Experiments in mice showed that blocking the stress hormone corticotropin-releasing hormone (CRH) selectively in this group of neurons from the hypothalamus erased the animals' natural fears.
Mice with the deletion readily walked elevated gangplanks, explored brightly lit areas and approached novel objects -- things normal mice avoid, the results showed.
CRH, discovered nearly 40 years ago, coordinates our physical and behavioural stress response, often termed the "fight-or-flight" response.
This response helps us survive in the face of threats, but when it is activated at the wrong time or too intensely, it can lead to anxiety and/or depression, the study said.
Targeting these neurons,(that releases Corticotropin-releasing hormone (CRH) gene) rather than the whole brain, could potentially provide a more effective treatment for anxiety and perhaps other psychiatric disorders, said Joseph Majzoub, researchers from the Boston Children's Hospital in the US.
In the study, using genetic engineering, the team selectively removed the CRH gene from about 1,000 nerve cells in the hypothalamus of mice.
The targeted cells were in the paraventricular nucleus, an area of the hypothalamus known to control the release of stress hormones such as cortisol.
The loss of CRH in those cells affected not only hormone secretion, but also dramatically reduced anxiety behaviours such as vigilance, suspicion, fear in the mice.
"Blocking just certain neurons releasing CRH would be enough to alter behaviour in a major way," Majzoub added.
In the above mentioned experiment, for example, the genetically altered mice were perfectly willing to venture onto an elevated maze, even the "open" section whose protective walls were removed.
Similarly, when the mice were presented with an open field, the modified mice explored much more of its center, rather than hang out at the periphery like the control mice.
Majzoub acknowledges that blocking CRH production in just a subset of neurons would be technically challenging in humans.
But if this could be done, it could be helpful for treating severe anxiety disorders or post-traumatic stress disorder (PTSD), said the paper published in the journal Molecular Psychiatry.
