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Article
VGLUT1 Synapses and P-Boutons on Regenerating Motoneurons After Nerve Crush
Journal of Comparative Neurology
  • Adam J. Schultz
  • Travis M. Rotterman
  • Anirudh Dwarakanath
  • Francisco J. Alvarez, Wright State University - Main Campus
Document Type
Article
Publication Date
4-1-2017
Abstract

Stretch-sensitive Ia afferent monosynaptic connections with motoneurons form the stretch reflex circuit. After nerve transection, Ia afferent synapses and stretch reflexes are permanently lost, even after regeneration and reinnervation of muscle by motor and sensory afferents is completed in the periphery. This loss greatly affects full recovery of motor function. However, after nerve crush, reflex muscle forces during stretch do recover after muscle reinnervation and reportedly exceed 140% baseline values. This difference might be explained by structural preservation after crush of Ia afferent synapses on regenerating motoneurons and decreased presynaptic inhibitory control. We tested these possibilities in rats after crushing the tibial nerve (TN), and using Vesicular GLUtamate Transporter 1 (VGLUT1) and the 65 kDa isoform of glutamic acid-decarboxylase (GAD65) as markers of, respectively, Ia afferent synapses and presynaptic inhibition (P-boutons) on retrogradely labeled motoneurons. We analyzed motoneurons during regeneration (21 days post crush) and after they reinnervate muscle (3 months). The results demonstrate a significant loss of VGLUT1 terminals on dendrites and cell bodies at both 21 days and 3 months post-crush. However, in both cellular compartments, the reductions were small compared to those observed after TN full transection. In addition, we found a significant decrease in the number of GAD65 Pboutons per VGLUT1 terminal and their coverage of VGLUT1 boutons. The results support the hypothesis that better preservation of Ia afferent synapses and a change in presynaptic inhibition could contribute to maintain or even increase the stretch reflex after nerve crush and by difference to nerve transection.

DOI
10.1002/cne.24244
Citation Information
Adam J. Schultz, Travis M. Rotterman, Anirudh Dwarakanath and Francisco J. Alvarez. "VGLUT1 Synapses and P-Boutons on Regenerating Motoneurons After Nerve Crush" Journal of Comparative Neurology Vol. 525 Iss. 13 (2017) p. 2876 - 2889 ISSN: 0021-9967
Available at: http://works.bepress.com/francisco_alvarez/101/