Fear and fear extinction learning (the gradual reduction of fear by repeated exposure to the feared object) are adaptive processes caused by molecular changes in specific brain circuits, and they're perturbed in conditions such as anxiety and post-traumatic stress disorder.
A new study by investigators reveals that the expression of a particular gene may function as a switch to regulate feelings of fear and its extinction. The findings point to a potential new target for diagnosing, treating, and preventing fear-related psychiatric illnesses.
The research, which is published in Nature Communications, focuses on neurons in the central amygdala that produce a corticotropin-releasing hormone (Crh) and are involved in the brain's response to threats. The scientists examined how different gene pathways are activated within Crh neurons after the expression or extinction of fear.
"This precise analysis utilized a new cell-type-specific technology called translating ribosome affinity purification, or TRAP, to identify gene expression only within the Crh amygdala cells," said co-senior author . "The results showed that diverse gene networks are activated or inhibited by fear versus extinction learning."
Additional analyses demonstrated that fear extinction learning requires that Crh neurons reduce their expression of a regulatory gene named CREB, which codes for a protein called cAMP response-element binding protein. Indeed, overexpression of CREB in Crh neurons in mice increased their fear response.
"CREB is well known to be involved in learning and memory, and these data suggest that it may act as a molecular switch that regulates expression of fear and its extinction," said co-senior author.
Targeting CREB expression in Crh neurons in the brain's amygdala may provide a better understanding of the mechanisms behind fear-based psychiatric illnesses and represent a promising treatment strategy.
Gene expression study identifies CREBs role in fear and its regulation
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