OVERALL OBJECTIVES: Our laboratory is devoted to the study of functional regeneration in the mammalian spinal cord. The model system under study is the spinal cord of the adult cat. Specifically, this project investigates the possibility that spindle group II afferents may generate new functional connections with spinal motoneurons. Synaptic sites are made available on these motoneurons as a consequence of temporary ischemia of the spinal cord, eliminating interneurons normally occupying about 95 percent of all synaptic sites on motoneurons. The fundamental question asked is whether spindle group II afferents sprout to form new functional contacts in response to the presence of newly-available synaptic sites, in the post-ischemic spinal cord. The existence of new group II-motoneuron synapses would be suggested by the presence of single fiber spindle group II EPSPs of unusually large magnitude (greater than 100 uV) or in an unusually large number of motoneurons (the percentage will depend upon the conduction velocity of the particular afferent). In addition, a number of other important questions will be asked concerning neuronal function in the post-traumatic cord: Are single fiber EPSPs then different in configuration (indicative of altered synaptic location on the soma-dendritic membrance)? Are different types of motoneurons contacted? Are denervated mononeurons more or less excitable (rheobase, repetitive firing properties)?

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS015913-08
Application #
3396551
Study Section
Neurology A Study Section (NEUA)
Project Start
1979-12-01
Project End
1989-03-31
Budget Start
1987-12-01
Budget End
1989-03-31
Support Year
8
Fiscal Year
1988
Total Cost
Indirect Cost
Name
University of Florida
Department
Type
Schools of Medicine
DUNS #
073130411
City
Gainesville
State
FL
Country
United States
Zip Code
32611
Mendell, L M; Munson, J B; Arvanian, V L (2001) Neurotrophins and synaptic plasticity in the mammalian spinal cord. J Physiol 533:91-7
Munson, J B; Johnson, R D; Mendell, L M (1999) Neurotrophin-3 and maintenance of muscle afferent function. Prog Brain Res 123:157-63
Gordon, T; Tyreman, N; Rafuse, V F et al. (1999) Limited plasticity of adult motor units conserves recruitment order and rate coding. Prog Brain Res 123:191-202
Mendell, L M; Johnson, R D; Munson, J B (1999) Neurotrophin modulation of the monosynaptic reflex after peripheral nerve transection. J Neurosci 19:3162-70
Munson, J B; McMahon, S B (1997) Effects of GDNF on axotomized sensory and motor neurons in adult rats. Eur J Neurosci 9:1126-9
Munson, J B; Foehring, R C; Mendell, L M et al. (1997) Fast-to-slow conversion following chronic low-frequency activation of medial gastrocnemius muscle in cats. II. Motoneuron properties. J Neurophysiol 77:2605-15
Taylor, J S; Friedman, R F; Munson, J B et al. (1997) Stretch hyperreflexia of triceps surae muscles in the conscious cat after dorsolateral spinal lesions. J Neurosci 17:5004-15
Munson, J B; Shelton, D L; McMahon, S B (1997) Adult mammalian sensory and motor neurons: roles of endogenous neurotrophins and rescue by exogenous neurotrophins after axotomy. J Neurosci 17:470-6
Gordon, T; Tyreman, N; Rafuse, V F et al. (1997) Fast-to-slow conversion following chronic low-frequency activation of medial gastrocnemius muscle in cats. I. Muscle and motor unit properties. J Neurophysiol 77:2585-604
Munson, J B; Johnson, R D; Mendell, L M (1997) NT-3 increases amplitude of EPSPs produced by axotomized group Ia afferents. J Neurophysiol 77:2209-12

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