title: Delaying the onset of treadmill exercise following peripheral nerve injury has different effects on axon regeneration and motoneuron synaptic plasticity.
abstract: Transection of a peripheral nerve results in withdrawal of synapses from motoneurons. Some of the withdrawn synapses are restored spontaneously, but those containing the vesicular glutamate transporter 1 (VGLUT1), and arising mainly from primary afferent neurons, are withdrawn permanently. If animals are exercised immediately after nerve injury, regeneration of the damaged axons is enhanced and no withdrawal of synapses from injured motoneurons can be detected. We investigated whether delaying the onset of exercise until after synapse withdrawal had occurred would yield similar results. In Lewis rats, the right sciatic nerve was cut and repaired. Reinnervation of the soleus muscle was monitored until a direct muscle (M) response was observed to stimulation of the tibial nerve. At that time, rats began 2 wk of daily treadmill exercise using an interval training protocol. Both M responses and electrically-evoked H reflexes were monitored weekly for an additional seven wk. Contacts made by structures containing VGLUT1 or glutamic acid decarboxylase (GAD67) with motoneurons were studied from confocal images of retrogradely labeled cells. Timing of full muscle reinnervation was similar in both delayed and immediately exercised rats. H reflex amplitude in delayed exercised rats was only half that found in immediately exercised animals. Unlike immediately exercised animals, motoneuron contacts containing VGLUT1 in delayed exercised rats were reduced significantly, relative to intact rats. The therapeutic window for application of exercise as a treatment to promote restoration of synaptic inputs onto motoneurons following peripheral nerve injury is different from that for promoting axon regeneration in the periphery.
authors: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.
authors: Jaclyn
authors: J
authors: Brandt
authors: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.
authors: Jonathan T
authors: JT
authors: Evans
authors: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.
authors: Taylor
authors: T
authors: Mildenhall
authors: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.
authors: Amanda
authors: A
authors: Mulligan
authors: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.
authors: Aimee
authors: A
authors: Konieczny
authors: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia.
authors: Samuel J
authors: SJ
authors: Rose
authors: Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia medae@emory.edu.
authors: Arthur W
authors: AW
authors: English
mesh_terms: D000818:Animals; D001369:Axons / Q000473:pathology*; D016552:Ergometry; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D009046:Motor Neurons / Q000473:pathology*; D009416:Nerve Regeneration / Q000502:physiology; D009473:Neuronal Plasticity; D059348:Peripheral Nerve Injuries / Q000503:physiopathology* / Q000628:therapy; D051381:Rats; D011917:Rats, Inbred Lew; D013569:Synapses / Q000473:pathology*; D009435:Synaptic Transmission; D013997:Time Factors; D016896:Treatment Outcome
keywords: exercise; nerve injury; regeneration; synaptic plasticity
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