THE ESSENTIAL
- Migraine affects 11 million people.
- Symptoms suggestive of autism most often appear before 36 months, they can be well before (before 18 months) or occur later.
Researchers at the Biological Institute of Salk have discovered a molecular pathway, in other words a set of chemical reactions, which allows the transmission of threatening images, sounds or smells in order to be afraid.
This molecule, called “CGRP”, gives the possibility to neurons from two different areas to gather threatening sensory signals into a single message, give it a negative connotation and send it to the amygdala. The latter will interpret this message in fear.
This study, published in the journal Cell Reportscould provide therapeutic solutions for fear-related disorders such as hypersensitivity disorders (autism, migraines, fibromyalgia) or post-traumatic stress disorder.
Tests carried out on mice
To arrive at these results, the research team conducted several experiments to test their hypotheses. They presented guinea pigs, otherwise known as mice, with multisensory threat signals while analyzing the activities of CGRP neurons using calcium imaging, which visualizes calcium in cells.
This process allowed the researchers to determine which sensory signal was linked to which set of neurons. The scientists determined the circuit taken by the signals, using colored fluorescent proteins. In addition, the scientists performed behavioral tests to assess fear and memory.
Two distinct areas of “CGRP” neurons
The findings show that two distinct areas of CGRP neurons, one in the thalamus and the other in the brainstem, diffuse into areas of the amygdala, forming two well-defined circuits. The two zones record sounds, smells, tastes or even images. Scientists have found that both circuits are important in creating bad memories.
“While mice were used in this study, the same brain regions also abundantly express CGRP in humans”says Han, one of the authors of the study. “This suggests that the circuits reported here may also be involved in psychiatric disorders related to threat perception.”
In the future, the authors wish to analyze disorders involving processing abnormalities such as migraines or autism spectrum disorders (ASD). “We haven’t tested it yet, but migraines might also activate these CGRP neurons in the thalamus and brainstem,” explains co-first author Sukjae Joshua Kang.
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