Summary
An examination of the precise mode of termination of the corticospinal system in the spinal cord of rodents has been conducted by use of light and electron microscope methods. This study confirms the position of the normal corticospinal tract in rodents in the ventralmost portion of the dorsal column white matter. Three to four days following unilateral sensorimotor cortex ablation, Nauta-Gygax and Fink-Heimer silver methods reveal a dorsomedial projection of degenerating debris into the dorsal horn from the contralateral corticospinal tract. Although the silver methods do not show degeneration at survival times earlier than two days, the electron microscope shows degenerating axons and synaptic knobs as early as 24 hours following cortical lesion. The degenerating synaptic knobs are found only in the dorsal regions of the dorsal horn subjacent to the substantia gelatinosa. They usually make synaptic contact with several small to medium sized dendrites. These terminals do not appear to participate in axosomatic or axoaxonal synapses. No degeneration is seen in the ipsilateral corticospinal tract, the lateral white columns, or the ventral horn of the spinal cord.
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References
Andersen, P., J.C. Eccles, Sears, T.A.: Presynaptic inhibitory action of cerebral cortex on spinal cord. Nature (Lond.) 194, 740–741 (1962).
—: Cortically evoked depolarization of primary afferent fibers in the spinal cord. J. Neurophysiol. 27, 63–77 (1964).
Barron, D.H.: The results of unilateral pyramidal section in the rat. J. comp. Neurol. 60, 45–55 (1934).
Bodian, D.: Synaptic types on spinal motoneurons: an electron microscope study. Bull. John Hopk. Hosp. 119, 16–45 (1966).
Brooks, C.M.: Studies on the cerebral cortex. II. Localized representation of hopping and placing reactions in the rat. Amer. J. Physiol. 105, 162–171 (1933).
Carpenter, D., Lundberg, A., Norrsell, U.: Effects from the pyramidal tract on primary afferents and on spinal reflex actions to primary afferents. Experientia (Basel) 18, 337–338 (1962).
—: Primary afferent depolarization evoked from the sensorimotor cortex. Acta physiol. scand. 59, 126–142 (1963).
Castro, A.J.: Motor performance in the rat following lesions of the frontal cortex. Anat. Rec. 166, 289 (1970).
Colonnier, M.: Synaptic patterns on different cell types in the different laminae of the cat visual cortex. An electron microscope study. Brain Res. 9, 268–287 (1968).
Coombs, J.S., Curtis, D.R., Landgren, S.: Spinal cord potentials generated by impulses in muscle and cutaneous fibers. J. Neurophysiol. 19, 452–467 (1956).
Douglas, A., Barr, M.L.: The course of the pyramidal tract in rodents. Rev. canad. Biol. 9, 118–122 (1950).
Dunkerley, G.B., Duncan, D.: A light and electron microscopic study of the normal and degenerating corticospinal tract in the rat. J. comp. Neurol. 137, 155–184 (1969).
Eccles, J.C.: The Physiology of Synapses. Berlin-Göttingen-Heidelberg-New York: Springer 1964.
Fetz, E.E.: Pyramidal tract effects on interneurons in cat lumbar dorsal horn. J. Neurophysiol. 31, 69–80 (1968).
Fink, R.P., Heimer, L.: Two methods for selective silver impregnation of degenerating axons and their synaptic endings in the central nervous system. Brain Res. 4, 369–374 (1967).
Glees, P.: Terminal degeneration within the central nervous system as studied by a new silver method. J. Neuropath. 5, 54–59 (1946).
Goodman, D.C., Jarrard, L.E., Nelson, J.F.: Corticospinal pathways and their sites of termination in the albino rat. Anat. Rec. 154, 462 (1966).
Guillery, R.W., Ralston, H.J.: Nerve fibers and terminals: electron microscopy after Nauta staining. Science 143, 1331–1332 (1964).
Haartsen, A.B.: Cortical projections to mesencephalon, pons, medulla oblongata and spinal cord: an experimental study in the goat and the rabbit. Thesis, Leiden 1962.
Hagbarth, D.E., Kerr, D.I.B.: Central influences on spinal afferent conduction. J. Neurophysiol. 17, 295–307 (1954).
Heimer, L.: Silver impregnation of degenerating axons and their terminals on epon-araldite sections. Brain Res. 12, 246–249 (1969).
—, Peters, A.: An electron microscope study of a silver stain for degenerating boutons. Brain Res. 8, 337–346 (1968).
Holmes, W.: A new method for impregnation of nerve axons in mounted paraffin sections. J. Path. Bact. (Lond.) 54, 132–136 (1942).
Jacobson, S.: An electron microscope study of Wallerian degeneration in the pyramidal tract. Neurology 17, (3) 298 (1967).
Jane, J.A., Campbell, C.B.G., Yashon, D.: Pyramidal tract: a comparison of two prosimian primates. Science 147, 153–155 (1965).
Kappers, A., Huber, G.C., Crosby, E.C.: The Comparative Anatomy of the Nervous System of Vertebrates, Including Man. Hafner Publishing Co., N.Y. 1936.
Karnorsky, M.T.: A formaldehyde-gluteraldehyde fixative of high osmolality for use in electron microscopy. J. Cell Biol. 27, 137 (1965).
King, J.L.: The corticospinal tract of the rat. Anat. Rec. 4, 245–252 (1910).
Linowiecki, J.: The comparative anatomy of the pyramidal tract. J. comp. Neurol. 24, 509–530 (1914).
Lund, J.S., Lund, R.D.: The termination of callosal fibers in the paravisual cortex of the rat. Brain Res. 17, 25–45 (1970).
Lundberg, A., Voorhoeve, P.: Effects from the pyramidal tract on spinal reflex arcs. Acta physiol. scand. 56, 201–219 (1962).
Martin, G.F., Dom, R.: The rubrospinal tract of the opossum (Didelphis virginiana). J. comp. Neurol. 138, 19–30 (1970).
—, Fisher, A.M.: A further evaluation of the origin, the course and the termination of the opossum corticospinal tract. J. neurol. Sci. 7, 177–187 (1968).
—, Megirian, D., Roebuck, A.: The corticospinal tract of the marsupial phalanger (Trichosurus vulpecula). J. comp. Neurol. 139, 245–258 (1970).
Nauta, W.J.H., Gygax, P.A.: Silver impregnation of degenerating axons in the central nervous system: a modified technic. Stain Technol. 29, 91–93 (1954).
Nyberg-Hansen, R., Brodal, A.: Sites of termination of corticospinal fibers in the cat. An experimental study with silver impregnation methods. J. comp. Neurol. 120, 369–391 (1963).
Ralston, H.J., III: The fine structure of neurons in the dorsal horn of the cat spinal cord. J. comp. Neurol. 132, 275–302 (1968).
Ranson, S.W.: The fasciculus cerebro-spinalis in the albino rat. Amer. J. Anat. 14, 411–424 (1913).
Reveley, I.L.: The pyramidal tract in the guinea pig (Cavia aperea). Anat. Rec. 9, 297–305 (1915).
Rexed, B.: The cytoarchitectonic organization of the spinal cord in the cat. J. comp. Neurol. 96, 415–496 (1954).
Richardson, K.L., Jarett, L., Finke, E.H.: Embedding in epoxy resins for ultrathin sectioning in electron microscopy. Stain Technol. 35, 313–323 (1960).
Scheibel, M.E., Scheibel, A.B.: Terminal axonal patterns in cat spinal cord. I. The lateral cortical spinal tract. Brain Res. 2, 333–350 (1966).
Simpson, S.: Quoted from Nathan, P.W. and M.C. Smith 1955 Long descending tracts in man. Brain 78, 248–303 (1902).
—: The pyramidal tract in the Canadian porcupine (Erethizion dorsatus, Linn.). Proc. Soc. exp. Biol. (N.Y.) 10, 4 (1912).
—: The pyramidal tract in the red squirrel (Sciurus hudsonius loqua) and chipmunk (Tamias striatus lysteri). J. comp. Neurol. 24, 137–160 (1914).
—: The pyramid tract in the striped gopher (Spermophilus tridicemlineatus). Quart. J. exp. Physiol. 8, 383 (1915).
Sprague, J.M., Ha, H.: The terminal fields of dorsal root fibers in the lumbosacral spinal cord of the cat and the dendritic organization of the motor nuclei. In: Progress in Brain Research, Vol. 11 (1964).
Torvik, A.: Afferent connections to sensory trigeminal nuclei, the nucleus of the solitary tract and adjacent structures. An experimental study in the rat. J. comp. Neurol. 106, 51–141 (1956).
Uchizono, K.: Characteristics of excitatory and inhibitory synapses in the central nervous system of the cat. Nature (Lond.) 207, 642–643 (1965).
Valverde, F.: The pyramidal tract in rodents. A study of its relations with the posterior column nuclei, dorsolateral reticular formation of the medulla oblongata, and cervical spinal cord. Z. Zellforsch. 71, 297–363 (1966).
Vaughn, J.E., Peters, A.: Aldehyde fixation of nerve fibers. J. Anat. (Lond.) 100, 687 (1966).
Venable, J.H., Coggeshall, R.: A simplified lead citrate stain for use in electron microscopy. J. Cell Biol. 25, 407–408 (1965).
Walberg, F.: An electron microscope study of terminal degeneration in the inferior olive of the cat. J. comp. Neurol. 125, 205–222 (1965).
Wall, P.D.: The laminar organization of dorsal horn and effects of descending impulses. J. Physiol. (Lond.) 188, 403–424 (1967).
Westrum, L.E.: A combination staining technique for electron microscopy. 1. Nervous tissue. J. Microscop. 4, 275–278 (1965).
Windle, W.F., Rhines, R., Rankin, J.: A Nissl method using buffered solutions of thionin. Stain Technol. 18, 77–90 (1943).
Young, J.Z.: The Life of Vertebrates. Oxford: Univ. Press, New York and Oxford 1962.
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Brown, L.T. Projections and termination of the corticospinal tract in rodents. Exp Brain Res 13, 432–450 (1971). https://doi.org/10.1007/BF00234340
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DOI: https://doi.org/10.1007/BF00234340