It is now known that a rather precise anatomical relationship exists between spinal motor neurons and the muscle fiber with which they make synaptic contacts. Single motor units within a muscle are aggregated into neuromuscular compartments, each of which is innervated by a primary branch of the muscle nerve, and the motor neurons innervating a compartment are topographically mapped in the spinal cord. This spatial relationship between motor neurons and muscle fibers is termed motor unit specificity (76). The proposed study will investigate the roles played by two normal processes of postnatal growth, input elimination and histogenetic cell death, in the establishment of motor unit specificity. At birth all mammalian muscle fibers receive synaptic input from more than one motor neuron but shortly thereafter all but one of these inputs are eliminated. Similarly, up to 30% of spinal motor neurons are reported to die postnatally. Experiments are proposed, using the compartmentalized cat lateral gastrocnemius muscle as a model (21-26), to test hypotheses that at least one role played by both input elimination and histogenetic cell death is the establishment of an adult pattern of motor unit specificity from a less precise pre-natal spinal cord-to-muscle projection. It is anticipated that the results of this project will be significant to motor control and developmental neurobiologists in helping to elucidate factors which contribute to the establishment and maintenance of precise synaptic connections in the nervous system, especially as related to the mechanisms underlying disorders of movement.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS020545-03
Application #
3400937
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1985-07-01
Project End
1989-03-31
Budget Start
1987-07-01
Budget End
1989-03-31
Support Year
3
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Emory University
Department
Type
Schools of Medicine
DUNS #
042250712
City
Atlanta
State
GA
Country
United States
Zip Code
30322
English, A W; Wolf, S L; Segal, R L (1993) Compartmentalization of muscles and their motor nuclei: the partitioning hypothesis. Phys Ther 73:857-67
Gatesy, S M; English, A W (1993) Evidence for compartmental identity in the development of the rat lateral gastrocnemius muscle. Dev Dyn 196:174-82
Roden, R L; Donahue, S P; Schwartz, G A et al. (1991) 200 kD neurofilament protein and synapse elimination in the rat soleus muscle. Synapse 9:239-43
Donahue, S P; English, A W; Roden, R L et al. (1991) Tenotomy delays both synapse elimination and myogenesis in rat lateral gastrocnemius. Neuroscience 42:275-82
English, A W (1990) Development of compartmentalized innervation of the rat gluteus maximus muscle. J Comp Neurol 301:104-13
Donahue, S P; English, A W (1989) Selective elimination of cross-compartmental innervation in rat lateral gastrocnemius muscle. J Neurosci 9:1621-7
English, A W; Weeks, O I (1989) Electromyographic cross-talk within a compartmentalized muscle of the cat. J Physiol 416:327-36
Donahue, S P; English, A W (1989) Use of formamide increases the number of detectable inputs to polyneuronally innervated mammalian skeletal muscle. J Neurosci Methods 28:239-44
Donahue, S P; Wood, J G; English, A W (1988) On the role of the 200-kDa neurofilament protein at the developing neuromuscular junction. Dev Biol 130:154-66
Donahue, S P; English, A W (1987) The role of synapse elimination in the establishment of neuromuscular compartments. Dev Biol 124:481-9