Functional distinction between NGF-mediated plasticity and regeneration of nociceptive axons within the spinal cord

This study explores how nerve growth factor (NGF) affects the sprouting and regeneration of specific pain-sensing nerve fibers (nociceptive axons) in the spinal cord after injury. The researchers found that while NGF can promote the regrowth of these fibers, the resulting pain responses differ depending on whether the fibers are simply sprouting in an uninjured spinal cord or regenerating after a spinal cord injury. Specifically, NGF-induced sprouting leads to chronic pain, whereas NGF-induced regeneration leads to a more normal protective pain response.

• 1
  NGF-induced sprouting of CGRP axons in normal animals resulted in a significant redistribution of synapses and cFos expression into the deeper dorsal horn, leading to severe chronic pain.
• 2
  Regeneration of only the CGRP axons showed a general reduction in synapses and cFos expression within laminae I and II and induced recovery of thermal nociceptive function close to normal baseline levels.
• 3
  Peripheral inflammation can induce mechanical allodynia after regeneration of peptidergic nociceptive axons, indicating that these axons maintain sensitization and can drive mechanical sensitivity under specific pathological conditions.