Cellular neuroscienceRegenerating supernumerary axons are cholinergic and emerge from both autonomic and motor neurons in the rat spinal cord
Section snippets
Experimental procedures
All animal procedures followed the guidelines of the NIH guide for the Care and Use of Laboratory Animals (NIH Publications No. 80-23, revised 1996) and were approved by the Chancellor’s Animal Research Committee at UCLA. Adult male Sprague–Dawley rats (n=14, 175–225g, Charles River Laboratories, Raleigh, NC, USA) were included in the studies. The animals were housed in a room with a 12-h light/dark cycle with food and water access ad libitum. Efforts were made to minimize the number of animals
Autonomic and motor neurons develop cholinergic supernumerary axons
Using IHC for ChAT, we studied the morphological features of autonomic and motor neurons in the L6 and S1 segments at 6 weeks after an L5–S2 ventral root avulsion and implantation of the L6 avulsed root into the spinal cord. ChAT IR neurons were detected in the ventral horn, intermediolateral nucleus, adjacent to the central canal, and occasionally in the dorsal horn, corresponding to previously described populations of motoneurons, PPNs, central canal cluster cells, and interneurons,
Discussion
We demonstrated that axotomized motoneurons and PPNs in the adult rat spinal cord developed ChAT IR supernumerary axons following a lumbosacral ventral root avulsion injury and acute implantation of an avulsed ventral root into the spinal cord. The supernumerary axons originated from either the soma or dendrites, exhibited an aberrant projection pattern, commonly extending into the lateral funiculus toward the site of the implanted root, and formed both bouton-like swellings and growth
Conclusion
We show that supernumerary axons originating from spinal cord neurons may develop in adult rats following a lumbosacral ventral root avulsion and subsequent implantation of an avulsed ventral root into the spinal cord. In addition, supernumerary axons can originate not only from motoneurons, but also autonomic neurons in the spinal cord. Furthermore, the presence of ChAT IR in these supernumerary axons and their terminal arbors with bouton-like swellings raises the possibility that
Acknowledgments
Supported by: NIH/NINDS NS042719, the Roman Reed Funds for Spinal Cord Injury Research of California, the Paralysis Project of America, and the ARCS Foundation. We would like to thank Dr. Matthew Schibler for excellent assistance with confocal microscopy at the Brain Research Institute/Carol Moss Spivak Cell Imaging Facility, UCLA.
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The longitudinal spinal cord injury: Lessons from intraspinal plexus, cauda equina and medullary conus lesions
2012, Handbook of Clinical NeurologyCitation Excerpt :For instance, the axotomized neurons show early and sustained cell body atrophy in combination with altered metabolism, which includes a markedly reduced synthesis of choline acetyl transferase during the first month after injury (Hoang et al., 2003). When preganglionic parasympathetic neurons survive following a root avulsion injury, i.e. supported by the reimplantation of lesioned roots into the conus medullaris, they may develop supernumerary axons, which emerge from the cell body or proximal dendrites, show a cholinergic phenotype, and express both GAP-43 and the low-affinity neurotrophic factor receptor p75 (Hoang et al., 2005). Such regenerative axons share many features of supernumerary axonal growth and altered neuronal polarity, encountered also in axotomized spinal motor neurons (Havtorn and Kellerth, 1987; Rose et al., 2001; MacDermid et al., 2002), and represent an interesting target for neurotrophic treatment strategies.
Out with the old, in with the new: Dendrite degeneration and regeneration
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