title: Compensatory plasticity restores locomotion after chronic removal of descending projections.
abstract: Homeostatic plasticity is an important attribute of neurons and their networks, enabling functional recovery after perturbation. Furthermore, the directed nature of this plasticity may hold a key to the restoration of locomotion after spinal cord injury. Here we studied the recovery of crawling in the leech Hirudo verbana after descending cephalic fibers were surgically separated from crawl central pattern generators shown previously to be regulated by dopamine. We observed that immediately after nerve cord transection leeches were unable to crawl, but remarkably, after a day to weeks, animals began to show elements of crawling and intersegmental coordination. Over a similar time course, excessive swimming due to the loss of descending inhibition returned to control levels. Additionally, removal of the brain did not prevent crawl recovery, indicating that connectivity of severed descending neurons was not essential. After crawl recovery, a subset of animals received a second transection immediately below the anterior-most ganglion remaining. Similar to their initial transection, a loss of crawling with subsequent recovery was observed. These data, in recovered individuals, support the idea that compensatory plasticity directly below the site of injury is essential for the initiation and coordination of crawling. We maintain that the leech provides a valuable model to understand the neural mechanisms underlying locomotor recovery after injury because of its experimental accessibility, segmental organization, and dependence on higher-order control involved in the initiation, modulation, and coordination of locomotor behavior.
authors: Department of Entomology, University of Minnesota, Saint Paul, Minnesota;
authors: Cynthia M
authors: CM
authors: Harley
authors: Department of Entomology, University of Minnesota, Saint Paul, Minnesota;
authors: Melissa G
authors: MG
authors: Reilly
authors: Department of Biology and Neuroscience Program, Saint Olaf College, Northfield, Minnesota.
authors: Christopher
authors: C
authors: Stewart
authors: Department of Entomology, University of Minnesota, Saint Paul, Minnesota;
authors: Chantel
authors: C
authors: Schlegel
authors: Department of Entomology, University of Minnesota, Saint Paul, Minnesota;
authors: Emma
authors: E
authors: Morley
authors: Graduate Program in Neuroscience, University of Minnesota, Saint Paul, Minnesota; and.
authors: Joshua G
authors: JG
authors: Puhl
authors: Department of Entomology, University of Minnesota, Saint Paul, Minnesota;
authors: Christian
authors: C
authors: Nagel
authors: Department of Biology and Neuroscience Program, Saint Olaf College, Northfield, Minnesota.
authors: Kevin M
authors: KM
authors: Crisp
authors: Department of Entomology, University of Minnesota, Saint Paul, Minnesota; Graduate Program in Neuroscience, University of Minnesota, Saint Paul, Minnesota; and mesce001@umn.edu.
authors: Karen A
authors: KA
authors: Mesce
mesh_terms: D000344:Afferent Pathways / Q000293:injuries* / Q000502:physiology*; D000818:Animals; D032125:Litchi / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D009416:Nerve Regeneration / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology*; D011597:Psychomotor Performance; D020127:Recovery of Function / Q000502:physiology*; D013997:Time Factors
keywords: central pattern generator; crawling; dopamine; homeostatic plasticity; locomotion