Study Finds Brain Cells that May Facilitate Bodily Reaction to Fear and Anxiety

At the University of North Carolina Health Care, neuroscientists have uncovered that activity of BNST cells after being artificially forced in mice resulted in production of an arousal response in the form of dilated pupils and faster heart rate along with the worsened anxiety-like behaviors.

These findings help in enlightening the bases of emotions generated from neurons and determined that the human-brain counterpart of the newly identified population of arousal-related neurons might be a target of future treatments for anxiety disorders, results published in Cell Reports.

Anxiety disorders, including depression and other associated disorders that are featured with an abnormally high or low arousal response can negatively affect a large proportion of the human population. It affects nearly tens of millions of adults in the United States alone.

The available treatments may alleviate the symptoms, but it may cause debilitating side effects. Moreover, the underlying root cause of these disorders is still not understood, an enormous challenge because of the complex and involved human brain.

Strong emotions such as anxiety and fear are accompanied by abnormal increased blood pressure, heart rate and respiration, and dilation of the eyes’ pupils. Altogether, these bodily responses to stress and anxiety are called “physiological arousal responses”, more commonly observed in individuals with psychiatric illnesses such as anxiety disorders and depression. In the study, researchers at the UNC School of Medicine have found a population of brain cells that actively drives such type of arousal responses.

“Focusing on arousal responses might offer a new way to intervene in psychiatric disorders,” said first author Jose Rodríguez-Romaguera, assistant professor in the UNC Department of Psychiatry and member of the UNC Neuroscience Center, and co-director of the Carolina Stress Initiative at the UNC School of Medicine.

Rodríguez-Romaguera and co-first author Randall Ung, PhD, an MD-PhD student and adjunct assistant professor in the Department of Psychiatry, together led this study when they were members of the UNC laboratory of Garret Stuber, PhD, now at the University of Washington. Rodríguez-Romaguera, Ung, Stuber and colleagues together examined and analysed a particular region of brain called amygdala, they particularly elucidated the BNST (bed nucleus of the stria terminalis) region in amygdala.

Source: Cell Reports

Mice was presented with unfavorable environment that induced fear and anxiety, such as, noxious odors. They then used a new technique called two-photon microscopy to directly image BNST Pnoc neurons in the mice brain cells to determine the induced fear/anxiety and reward behaviors, respectively, along with the appropriate arousal responses.

Furthermore, researchers used other techniques called optogenetics that genetically engineered brain cells using light to artificially force the cells, driving the activity of the BNST Pnoc neurons. They found that artificial forcing BNST Pnoc activity triggered a pupillary response and increased heart rate. Researchers in the study find the BNST region as a potential region to act as target for future psychiatric drugs.

“This work not only identifies a new population of neurons implicated in arousal and anxiety, but also opens the door for future experiments to systematically examine how molecularly defined cell types contribute to complex emotional and physiological states,” Stuber said.

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