This project is concerned with the effects of injury on the early development and differentiation of spinal motoneurons in the bullfrog tadpole. The long-term goal is to understand the mechanisms whereby developmental processes may ameliorate the consequences of damage to the nervous system. Studies such as those proposed here are not feasible in mammals because of the fragility and inaccessibility of the fetus in utero. The relatively large size of the bullfrog tadpole, even at the initial stages of motoneuron birth and differentiation, will allow the effects of axotomy on motoneuron maturation and on regulation of motoneuron number to studied in detail. The specific areas to be investigated include examining the role of the target in development, comparing effects of disconnection from the target versus axonal injury in development, and determining the conditions for motoneuronal survival following axotomy. These studies will involve quantitative light microscopy and electrophysiological recordings. A particular advantage of the bullfrog tadpole for these studies is that the isolated nervous system exhibits rhythmic discharges which, in the intact animal, underlie locomotion. A major focus of the electrophysiological studies will be to examine the effects of injury and disconnection from the target on the development of locomotor circuitry in the spinal cord, In addition, the effects of axotomy on the development and maintenance of monosynaptic inputs to the injured motoneurons will be determined.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
2R01NS016030-07A1
Application #
3396621
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1980-05-01
Project End
1990-06-30
Budget Start
1987-07-01
Budget End
1988-06-30
Support Year
7
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Type
Schools of Medicine
DUNS #
078861598
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Popken, G J; Farel, P B (1997) Sensory neuron number in neonatal and adult rats estimated by means of stereologic and profile-based methods. J Comp Neurol 386:8-15
Meeker, M L; Farel, P B (1997) Neuron addition during growth of the postmetamorphic bullfrog: sensory neuron and axon number. J Comp Neurol 389:569-76
Popken, G J; Farel, P B (1996) Reliability and validity of the physical disector method for estimating neuron number. J Neurobiol 31:166-74
St Wecker, P G; Baek, J K; Farel, P B (1995) Principal neurons of the lumbar sympathetic ganglia increase in number with body size. J Comp Neurol 357:117-23
St Wecker, P G; Farel, P B (1994) Hindlimb sensory neuron number increases with body size. J Comp Neurol 342:430-8
Meeker, M L; Farel, P B (1993) Coincidence of Schwann cell-derived basal lamina development and loss of regenerative specificity of spinal motoneurons. J Comp Neurol 329:257-68
Farel, P B; Wray, S E; Meeker, M L (1993) Size-related increase in motoneuron number: evidence for late differentiation. Brain Res Dev Brain Res 71:169-79
Farel, P B; Meeker, M L (1993) Developmental regulation of regenerative specificity in the bullfrog. Brain Res Bull 30:483-90
Farel, P B; St Wecker, P G; Wray, S E (1992) Neuron addition in the postmetamorphic frog. Exp Gerontol 27:111-24
Farel, P B; Wray, S E (1992) Neuromuscular specificity following cross-stage hindlimb transplantation. Exp Neurol 116:180-8

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