Regeneration of supraspinal axons after complete transection of the thoracic spinal cord in neonatal opossums (Monodelphis domestica).
These studies define the time table and origin of supraspinal axons regenerating across a complete spinal transection in postnatal Monodelphis domestica. After lumbar (L1) spinal cord injection of fluorophore-dextran amine conjugate on postnatal (P) day 4, a consistent number of neurons could be labeled. The numbers of labeled neurons remained stable for several weeks, but subsequently declined by P60 in control animals and by P35 in animals with complete spinal transection (T4-T6) performed at P7. In control animals, 25-40% of neurons labeled with a fluorophore injected (L1) at P4 could also be double-labeled by a second fluorophore injected (T8-T10) at different older ages. In spinally transected animals, total numbers of neurons labeled with the second marker were initially lower compared with age-matched controls, but were not significantly different by 3 weeks after injury. The proportion of double-labeled neurons in spinally transected animals increased from approximately 2% 1 week after injury (P14) to approximately 50% by P60, indicating that a substantial proportion of neurons with axons transected at P7 is able to regenerate and persist into adulthood. However, the proportion of axons originating from regenerating neurons made only a small contribution at older ages to total numbers of fibers growing through the injury site, because much of development of the spinal cord occurs after P7. Evidence was obtained that degenerating neurons with both apoptotic and necrotic morphologies were present in brainstem nuclei; the number of neurons with necrotic morphology was much greater in the brainstem of animals with spinal cords transected at P7.
Fry
Elizabeth Jane
EJ
Department of Pharmacology, University of Melbourne, Parkville, Victoria 3010, Australia.
Stolp
Helen Bronwyn
HB
Lane
Michael Aron
MA
Dziegielewska
Katarzyna Magdalena
KM
Saunders
Norman Ruthven
NR
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000737:chemistry / Q000502:physiology*; D001933:Brain Stem / Q000737:chemistry / Q000502:physiology*; D009416:Nerve Regeneration / Q000502:physiology*; D009434:Neural Pathways / Q000737:chemistry / Q000502:physiology; D009893:Opossums / Q000502:physiology*; D013119:Spinal Cord Injuries; D013904:Thoracic Vertebrae