AXONAL REGENERATION IN LAMPREY SPINAL CORD

The study investigates axonal regeneration in lamprey spinal cords after transection at two levels: rostral (near the gills) and caudal (near the cloaca). The researchers used horseradish peroxidase (HRP) to trace the regeneration of giant reticulospinal axons (RAs), dorsal cells (DCs), and giant interneurons (GIs). After 40 days, proximally transected RAs showed more regeneration than distally transected ones, suggesting that the regenerative capacity of RAs may decrease with the distance of axotomy from the cell body. Regeneration distance and branching peaked between 40 and 100 days, followed by a tendency toward neurite retraction. The spinal cord of larval sea lamprey is presented as a valuable model for studying regeneration in the vertebrate central nervous system. Its use allows for the demonstration of axonal regeneration of individual identified neurons both morphologically and electrophysiologically.

• 1
  Proximally transected RAs regenerated more extensively than distally transected RAs, suggesting a correlation between regenerative capacity and proximity to the cell body.
• 2
  Regeneration of proximally transected RAs peaked between 40 and 100 days, followed by a tendency toward neurite retraction, indicating that axonal regeneration does not continue indefinitely.
• 3
  Axons of dorsal cells (DCs) and giant interneurons (GIs) also demonstrated regenerative capacity, with GIs regenerating anteriorly up to 1.3 mm beyond the scar and DCs regenerating at least as well as those located below a rostral transection.