Summary
The ventral roots L7 and S1 of the owl monkeyAotus trivirgatus, were examined by electron microscopy. On average, these roots contain 2950 and 1837 myelinated axons respectively. In both roots the myelinated axons have bimodal size distributions, but the S1 root contains more small myelinated axons. Both roots contain a substantial proportion of unmyelinated axon profiles (UAP). In the L7 root the proportion of UAP decreases as the spinal cord is approached, from 19% distally to 5% in the juxtamedullary rootlets. Unmyelinated and very small myelinated CNS-type axons have not been observed in the L7 transitional region. The average S1 root contains some 40% unmyelinated axons at all examined proximo-distal levels. Unmyelinated/ very small myelinated axons are easily found on the CNS side of the S1 transitional region, in direct relation to motoraxon bundles. Bundles of unmyelinated and small myelinated axons occur in the ventral pia mater of both segments. The unmyelinated axons in the L7 root of the owl monkey appear to be arranged like those in the feline L7 ventral root, possibly representing afferents. It is likely that most unmyelinated and small myelinated axons in the ventral root S1 are autonomic efferents.
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References
Applebaum ML, Clifton GL, Coggeshall RE, Coulter JD, Vance WH, Willis WD (1976) Unmyelinated fibres in the sacral 3 and caudal l ventral roots of the rat. J Physiol (Lond) 256:557–572
Azerad J, Hunt CC, Laporte Y, Pollin B, Thiesson D (1986) Afferent fibers in cat ventral roots: electrophysiological and histological evidence. J Physiol (Lond) 379:229–243
Beattie MS, Bresnahan JC, Mawe GM, Finn S (1987) Distribution and ultrastructure of ventral root afferents to lamina I of the cat sacral spinal cord. Neurosci Lett 76:1–6
Berthold C-H (1974) A comparative morphological study of the developing node-paranode region in lumbar spinal roots. I. Electron microscopy. Neurobiology 4:82–104
Berthold C-H, Carlstedt T (1977) Observations of the morphology at the transition between the the peripheral and the central nervous system in the cat. II. General organisation of the transitional region. Acta Physiol Scand [Suppl] 446:23–42
Carlstedt T (1977) Observations on the morphology at the transition between the peripheral and the central nervous system in the cat. IV. Unmyelinated fibres in S1 dorsal rootlets. Acta Physiol Scand [Suppl] 446:61–72
Chung JM, Lee KH, Endo K, Coggeshall RE (1983) Activation of central neurons by ventral root afferents. Science 222:934–935
Chung JM, Lee KH, Kim J, Coggeshall RE (1985) Activation of dorsal horn cells by ventral root stimulation in the cat. J Neurophysiol 54:261–272
Chung K, Kang HS (1987) Dorsal root ganglion neurons with central processes in both dorsal and ventral roots in rats. Neurosci Lett 80:202–206
Coggeshall RE (1980) Law of separation of function of the spinal roots. Physiol Rev 60:716–755
Coggeshall RE, Ito H (1977) Sensory fibres in ventral roots L7 and S1 in the cat. J Physiol (Lond) 267:215–235
Coggeshall RE, Coulter JD, Willis WD (1973) Unmyelinated fibers in the ventral root. Brain Res 57:229–233
Coggeshall RE, Coulter JD, Willis WD (1974) Unmyelinated axons in the ventral roots of the cat lumbosacral enlargement. J Comp Neurol 153:39–58
Coggeshall RE, Applebaum ML, Stubbs TB, and Sykes MT (1975) Unmyelinated axons in human ventral roots, a possible explanation for the failure of dorsal rhizotomy to relieve pain. Brain 98:157–166
Coggeshall RE, Emery DG, Ito H, Maynard CW (1977) Unmyelinated and small myelinated axons in rat ventral roots. J Comp Neurol 173:175–184
Coggeshall RE, Maynard CW, Langford LA (1980) Unmyelinated sensory and preganglionic fibers in rat L6 and S1 ventral spinal roots. J Comp Neurol 193:41–47
Cranefield PF (1974) The way in and the way out. Futura, New York
Dalsgaard C-J, Risling M, Cuello C (1982) Immunohistochemical localization of substance P in the lumbosacral spinal pia mater and ventral roots of the cat. Brain Res 246:168–171
Duncan DA (1932) A determination of the number of unmyelinated fibers in the ventral roots of the rat, cat and rabbit. J Comp Neurol 55:459–471
Frykholm R, Hyde J, Norlén G, Skoglund CR (1953) On pain sensations produced by stimulation of ventral roots in man. Acta Physiol Scand 29:455–469
de Groat WD, Krier J (1975) Preganglionic C-fibers: a major component of the sacral autonomic outflow to the colon of the cat. Pflügers Arch 359:171–176
Hebel R, Stromberg MW (1986) Anatomy and embryology of the laboratory rat. Bio Med, Wörthsee FRG
Hosobuchi Y (1980) The majority of unmyelinated afferent axons in human ventral roots probably conduct pain. Pain 8:167–180
Häbler H-J, Jänig W, Koltzenburg M, McMahon SB (1990) A quantitative study of the central projection patterns of unmyelinated ventral root afferents in the cat. J Physiol (Lond) 422:265–287
Karnes J, Robb R, O'Brien PC, Lambert EH, Dyck PJ (1977) Computerized image recognition for morphometry of nerve: attribute of shape of sampled transverse sections of myelinated fibres which best estimates their average diameter. J Neurol Sci 34:43–51
Kim J, Chung JM (1985) Electrophysiological evidence for the presence of fibres in continuity between dorsal and ventral roots in the cat. Brain Res 338:355–359
Kim J, Shin HK, Chung JM (1987) Many ventral root afferent fibres in the cat are third branches of dorsal root ganglion cells. Brain Res 417:304–314
Kopsch F (1914) Rauber's Lehrbuch der Anatomic des Menschen. Abt. 5: Nervensystem. 10th edn. Thieme, Leipzig
Light AR, Metz CB (1978) The morphology of spinal cord efferent and afferent neurons contributing to the ventral roots of the cat. J Comp Neurol 179:501–516
Lindblom K, Rexed B (1948) Spinal nerve injury in dorsolateral protrusions of lumbar disks. J Neurosurg 5:413–432
Longhurst JC, Mitchell JH, Moore MB (1980) The spinal cord ventral root: an afferent pathway of the hind-limb pressor reflex in cats. J Physiol (Lond) 301:467–476
Maynard CW, Leonard RB, Coulter D, Coggeshall RE (1977) Central connections of ventral root afferents as demonstrated by the HRP method. J Comp Neurol 172:601–608
Remahl S, Hildebrand C (1982) Changing relation between onset of myelination and axon diameter range in developing feline white matter. J Neurol Sci 54:33–45
Risling M, Hildebrand C (1982) Occurrence of unmyelinated axon profiles at distal, middle and proximal levels in the ventral root L7 of cats and kittens. J Neurol Sci 56:219–231
Risling M, Remahl S, Hildebrand C, Aldskogius H (1980) Structural changes in kittens ventral and dorsal roots L7 after early postnatal sciatic nerve transection. Exp Neurol 67:265–279
Risling M, Dalsgaard C-J, Cukierman A, Cuello C (1984) Electron microscopic and immunchistochemical evidence that unmyelinated ventral root axons make U-turns or enter the spinal pia mater. J Comp Neurol 225:53–63
Risling M, Dalsgaard C-J, Terenius L (1985) Neuropeptide Y-like immunoreactivity in the lumbosacral pia mater in normal cats and after sciatic neuroma formation. Brain Res 358:372–375
Risling M, Hildebrand C, Dalsgaard C-J (1987) Unmyelinated axons in spinal ventral roots and motor cranial nerves. Do these fibres have a role in somatovisceral sensation? In: Schmidt RF, Schaible H-G, Vahle-Hinz C (eds) Fine afferent nerve fibres and pain. VCH Verlagsgesellschaft, Weinheim, pp 35–44
Romanes G (1951) The motor cell columns of the lumbo-sacral spinal cord of the cat. J Comp Neurol 94:313–358
Shecan D (1941) Spinal autonomic outflows in man and monkey. J Comp Neurol 75:341–370
Skoglund S, Romero C (1965) Postnatal growth of spinal nerves and roots. A morphological study in the cat with physiological correlations. Acta Physiol Scand, [Suppl 260] 66:1–50
Stevens RT, Hodge Jr CJ, Apkarian AV (1983) Catecholamine varicosities in cat dorsal root ganglion and spinal ventral roots. Brain Res 261:151–154
Vergara I, Oberpaur B, Alvarez J (1986) Ventral root nonmedullated fibers: proportion, calibers and microtubular content. J Comp Neurol 248:550–554
White JC, Sweet WH (1955) Pain — its mechanisms and neurosurgical control. Thomas, Springfield, Ill
Yamamoto T, Takahashi K, Satomi H, Ise H (1977) Origins of primary afferent fibres in the spinal ventral roots in the cat as demonstrated by the horseradish peroxidase method. Brain Res 126:350–354
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Karlsson, M., Hildebrand, C. & Warnborg, K. Fibre composition of the ventral roots L7 and S1 in the owl monkey (Aotus trivirgatus). Anat Embryol 184, 125–132 (1991). https://doi.org/10.1007/BF00942743
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DOI: https://doi.org/10.1007/BF00942743