Role of neurons expressing the neurotransmitter calcitonin gene-related peptide in experiencing pain
When nerves are damaged, the body’s normal pain response can malfunction, either producing stronger feelings of pain, or reacting to events that would not normally be painful. For patients suffering from mechanical allodynia, the slightest touch can cause debilitating pain. Several mechanisms are likely to play a role in this condition, but one pathway may involve the neurotransmitter CGRP, released by sensory nerves. To investigate this, researchers genetically engineered mice to link CGRP to a fluorescent marker, allowing them to identify a previously-unsuspected group of neurons expressing CGRP in the spinal cord (pictured, with neurons in red). These neurons typically showed little activity in response to mechanical stimulation, such as brushing the mice’s paws, but were strongly activated by the same touch after a nerve injury. Artificially activating these neurons also made mice more sensitive to touch, suggesting the hyperexcitability of CGRP-expressing neurons after nerve damage could contribute to allodynia.
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