One of the fundamental rules regarding the organization of the spinal cord is that sensory information enters through the dorsal roots and the ventral roots carry motor commands. This important generalization is challenged recently by the discovery of large numbers of afferent fibers in the ventral root. However, the functional importance of these ventral root afferents is yet to be demonstrated. The long term goal of the present proposal is to demonstrate the importance of the ventral root afferent fibers in sensory functions with special reference to nociception. To accomplish this goal, neurophysiological methods are employed first to demonstrate that a large number of dorsal horn cells in the cat spinal cord can be activated by ventral root stimulation. The sensory capacity of the dorsal horn cells that receive the ventral root input will be characterized in relation to the sensory function of the ventral root afferents. Attempts will be made to determine the peripheral origin of the afferent fibers in the ventral root and the central destination of the dorsal horn cells which are activated by the ventral root afferents by utilizing both anatomical and physiological methods. Studying the responses of the spinal cells to natural stimuli and determining the central destination of the processes of these cells should provide clues as to the sensory function of the ventral root afferents. Finally, the possible nociceptive role of the ventral root afferents will be tested on primate spinothalamic tract cells by observing the responsiveness of these cells to ventral root stimulation. This is because ventral root afferents have been implicated in nociception and the primate spinothalamic tract is the best established nociceptive tract in an animal model. Presumably these studies will have an impact of both basic and clinical significance. For example, elucidation of the organization of a previously unstudied group of primary afferents cannot help but improve our general understanding of sensory organization and such information will be important in evaluating the effects of dorsal rhizotomy and dorsal root ganglionectomy in the treatment of chronic segmental pain, which is so disabling in certain pathologic conditions in humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Modified Research Career Development Award (K04)
Project #
5K04NS000995-05
Application #
3074856
Study Section
Communication Sciences and Disorders (CMS)
Project Start
1985-09-01
Project End
1990-08-31
Budget Start
1989-09-01
Budget End
1990-08-31
Support Year
5
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Type
Schools of Medicine
DUNS #
041367053
City
Galveston
State
TX
Country
United States
Zip Code
77555
Chung, B S; Sheen, K; Chung, J M (1991) Evidence for invasion of regenerated ventral root afferents into the spinal cord of the rat subjected to sciatic neurectomy during the neonatal period. Brain Res 552:311-9
Nam, S C; Kim, K J; Leem, J W et al. (1990) Increased number of unmyelinated fibers in the ventral root after peripheral neurectomy in adult rat. Neurosci Lett 116:40-4
Baik-Han, E J; Kim, K J; Chung, J M (1990) Prolonged ongoing discharges of sensory nerves as recorded in isolated nerves in the rat. J Neurosci Res 27:219-27
Baik-Han, E J; Kim, K J; Chung, J M (1989) Electrophysiological evidence for the presence of looping myelinated afferent fibers in the rat ventral root. Neurosci Lett 104:65-70
Oh, U T; Kim, K J; Baik-Han, E J et al. (1989) Electrophysiological evidence for an increase in the number of ventral root afferent fibers after neonatal peripheral neurectomy in the rat. Brain Res 501:90-9
Paik, K S; Nam, S C; Chung, J M (1989) Different classes of cat spinal neurons display differential sensitivity to sodium pentobarbital. J Neurosci Res 23:107-15
Nam, S C; Kim, K J; Leem, J W et al. (1989) Fiber counts at multiple sites along the rat ventral root after neonatal peripheral neurectomy or dorsal rhizotomy. J Comp Neurol 290:336-42
Paik, K S; Nam, S C; Chung, J M (1988) Differential inhibition produced by peripheral conditioning stimulation on noxious mechanical and thermal responses of different classes of spinal neurons in the cat. Exp Neurol 99:498-511
Kim, J; Shin, H K; Nam, S C et al. (1988) Proportion and location of spinal neurons receiving ventral root afferent inputs in the cat. Exp Neurol 99:296-314