Delayed Treadmill Training and Synaptic Stripping of Axotomized Motoneurons Open Access

Wilson, Natalee Kay (2011)

Permanent URL: https://etd.library.emory.edu/concern/etds/q524jp48w?locale=en
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Abstract

Delayed Treadmill Training and Synaptic Stripping of Axotomized Motoneurons
By Natalee Kay Wilson
When a peripheral nerve is injured, sensory and motor axons in the periphery are disconnected from the central nervous system (CNS). In addition, synaptic inputs withdraw from the somata and proximal dendrites of the injured motoneuron, a process known as synaptic stripping. After moderate daily treadmill training, the expected loss of synaptic inputs onto axotomized motoneurons due to synaptic stripping is not observed. Whether this effect of treadmill training is due to the prevention of the withdrawal of synaptic inputs or a restoration of synapses is not clear. In this study, the onset of treadmill training was delayed until one week following peripheral nerve transection. At that time, substantial withdrawal of synapses from the axotomized motoneurons had occurred. The ability of treadmill training to restore synapses onto these motoneurons was evaluated. Synaptic coverage was assayed by measuring the proportion of somata and proximal dendrites of retrogradely labeled motoneurons covered by terminals immunopositive for markers of excitatory VGLUT1 and inhibitory GAD67 synapses. The coverage of axotomized motoneurons by terminals containing VGLUT1 in delayed trained mice was similar to that found in intact controls, suggesting a restoration of VGLUT1+ boutons onto the somata and proximal dendrites of the motoneuron. The expected loss of GAD67+ boutons that was observed in axotomized motoneurons in untrained mice was not found in trained mice, strongly suggesting that the delayed treadmill training had a restorative effect. Thus, if treadmill training is delayed by one week after nerve transection, the anticipated loss of synaptic coverage on the axotomized motoneurons does not occur. This is evidence for treadmill training having a restorative effect on the stripped synapses.

Delayed Treadmill Training and Synaptic Stripping of Axotomized Motoneurons
By
Natalee Kay Wilson
B.S., Emory University, Biology
Advisor: Arthur English, Ph.D.
A thesis submitted to the Faculty of the
James T. Laney School of Graduate Studies of Emory University
in partial fulfillment of the requirements for the degree of
Master of Science
in Biology
2011

Table of Contents

Table of Contents

I. Introduction 1

II. Methods 7
Animals 7
Muscle Injections/Retrograde Labeling 7
Surgical Methods 7

Treadmill Training 8
Immunohistochemistry 8
Image Analysis 9
Statistical Analysis 10


III. Results 11
Effect of delayed treadmill training on synaptic coverage by VGLUT1+ terminals 11

Effect of delayed treadmill training on synaptic coverage by GAD67+ terminals 13


IV. Discussion 15


V. Tables 18
Table 1. Groups of mice used in this study 18


VI. References 19


VII. Figures 23
Figure 1. Retrogradely labeled motoneurons (red) with synaptic boutons immunopostive for VGLUT1 (blue) and GAD67 (green). 23
Figure 2. Retrogradely labeled motoneuron with GAD67 and Profile plot 24
Figure 3. Effect of delayed treadmill training on VGLUT1+ synapses 25

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