Predator-like scent activates an anxiety-related brain circuit in mice
Anxiety disorders are some of the most common psychiatric conditions, estimated to affect around 4.4% of people worldwide, according to the World Health Organization. While neuroscientists have been studying these disorders for decades, their neural underpinnings are not yet fully understood.
Researchers at Guangdong Institute of Intelligence Science and Technology, Beijing Normal University, and the Chinese Academy of Sciences have identified a brain pathway that contributes to anxiety-like responses in mice. The study, published in Molecular Psychiatry, involved exposing mice to predator-like odors and electric shocks.
Single-cell calcium imaging was used to examine neuronal activity in response to these stimuli. The researchers found that neurons in the anterior and middle insular cortex (a/mIC) activated by the predator odor and footshock sent signals to the parabrachial nucleus (PBN) in the brainstem. This pathway then extended to the thalamus.
The activation of these neurons, particularly those that also respond to the predator odor, was linked to increased anxiety-like behavior in the mice. Further experiments showed that exposure to the predator-like odor increased corticotropin-releasing factor (CRF) signals in the PBN, which enhanced neuronal excitability and facilitated firing in neurons connected to the a/mIC.
When the researchers blocked this pathway or CRF signaling in the PBN, the mice exhibited less anxiety-like behavior in response to the predator-like odor. The study also found that human brain scans of individuals with anxiety symptoms showed stronger functional coupling within a putative homologous insular cortex–parabrachial nucleus–posterior paraventricular thalamus network, with stronger links correlating to more severe symptoms.
This research could help unravel the neural underpinnings of anxiety disorders and potentially lead to new treatment approaches.
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