A recent study published in the journal Molecular Psychiatry indicates that specific hypothalamus neurons play a key role in our experience of anxiety.
Researchers found that blocking the release of corticotropin-releasing hormone (CRH) in the hypothalamus neurons of lab mice neutralized their fears, allowing them to explore an unfamiliar environment without trepidation.
Almost 40 years ago, scientists discovered that the stress hormone CRH coordinates the “fight-or-flight” response. Fight-or-flight refers to the body’s mental and physical reactions that occur in frightening situations. These reactions prepare us to deal with and survive actual threats. However, if the response is extremely intense, or repeatedly triggered in non-threatening situations, anxiety or depression may ensue.
Anti-anxiety drugs earlier developed to block CRH have proven disappointing. “Blocking CRH receptors all over the brain doesn’t work,” said researcher Rong Zhang, PhD., Boston Children’s Hospital. “It may be that CRH has different effects depending on where in the brain it is produced."
Narrowing The CRH Focus
By implementing genetic engineering tools, Zhang and her colleagues were able to focus on a small area of the brain, removing CRH from approximately 1,000 hypothalamus nerve cells in mice. These cells were in the tiny paraventricular nucleus, a section of the hypothalamus regulating the release of stress hormones.
The researchers were surprised to find the elimination of CRH in the paraventricular nucleus not only altered hormone secretion, but significantly diminished anxiety behaviors - watchfulness, alarm, suspicion - in the mice. “It was a robust finding: every parameter we looked at indicated that this animal was much less inhibited,” said researcher Joseph Majzoub, MD.
The investigators were also intrigued to find that CRH secreted from the paraventricular nucleus travels to more areas in the brain than earlier thought, including areas responsible for behavioral stress responses.
While these CRH findings shed light on the problem of anxiety, blocking the CRH of specific neurons in humans presents a major technical challenge, so putting this new information to practical use will take time.
"Blocking just certain neurons releasing CRH would be enough to alter behavior in a major way," says Majzoub. "We don't know how to do that, but at least we have a starting point."
Source: Science Daily
Photo credit: Jon Rawlinson