Conditioning Lesions Enhance Axonal Regeneration of Descending Brain Neurons in Spinal-Cord-Transected Larval Lamprey

Researchers investigated how initial spinal cord injuries, called “conditioning lesions,” affect nerve regeneration after a second injury in larval lampreys. They found that a conditioning lesion could improve the ability of brain neurons to regrow their axons after a spinal cord transection. The study involved performing an initial spinal cord transection at either 30% or 50% of the body length, followed by a second transection at 10% body length after varying delay times. The extent of axonal regeneration was then assessed. The results suggest that conditioning lesions “prime” brain neurons, making them more capable of regenerating axons after a subsequent spinal cord injury, potentially by speeding up the initial regrowth process.

• 1
  Conditioning lesions at 30% body length, with a two-week delay before a test lesion and a four-week recovery period, significantly enhanced axonal regeneration of descending brain neurons.
• 2
  Hemi-conditioning lesion experiments confirmed that direct injury (axotomy) to the nerve cells, rather than general factors released at the injury site, is primarily responsible for the enhanced regeneration.
• 3
  The study suggests that conditioning lesions may reduce the initial delay or increase the initial rate of axonal outgrowth, contributing to the enhanced regeneration observed.