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Transneuronal degeneration in the Rolando substance of the primate spinal cord evoked by axotomy-induced transganglionic degenerative atrophy of central primary sensory terminals
Authors:Elizabeth Knyihár-Csillik  Pasko Rakic  Prof. Dr. Bert Csillik
Affiliation:(1) Department of Anatomy, Albert Szent-Györgyi Medical University, Szeged, Hungary;(2) Section of Neuroanatomy, Yale University, School of Medicine, New Haven, Connecticut, USA;(3) Department of Anatomy, Albert Szent-Györgyi Medical University, Kossuth Lajos sgt. 40, P.O.Box 512, H-6701 Szeged, Hungary
Abstract:Summary Transection of the sciatic nerve in Rhesus monkeys and the consequent transganglionic degenerative atrophy (TDA) of central terminals of primary afferents result in transneuronal degeneration of substantia gelatinosa (SG) cells. Severe degeneration is characterized by an increased electron density of the nucleus and by conspicuous shrinkage of the cytoplasm, mitochondrial swelling, dilation of cisterns of the rough-surfaced endoplasmic reticulum, accumulation of free ribosomes and an electron-dense material in the cytoplasm. In the mild form, dilation of cisternal elements of the endoplasmic reticulum, swollen mitochondria and accumulation of free ribosomes takes place. About 10% of SG cells in segment L5 undergo the severe form whereas the rest shows signs of the mild form. Cytoplasmic alterations that occur during transneuronal degeneration seem to start at the level of subsurface cisterns. Dendrites and axons of transneuronally degenerating SG cells also show a conspicuous electron density. By analyzing the synaptic relationships of such ldquodarkenedrdquo dendrites, connections in the upper dorsal horn can be deciphered. Modular units of the primary nociceptive analyzer that evaluate noxious and innocuous inputs on the basis of thin versus thick (AdeltaC/Abeta) afferent activity and subjecting them to descending control appear to be recruited from structurally dispersed elements of synaptic glomeruli. These are arranged alongside dendritic processes of large antenna cells which relay impulses to projection cells of the spinothalamic tract.
Keywords:Spinal cord  Transganglionic degenerative atrophy  Transneuronal degeneration  Subsurface cisterns  Connections  Wiring  Rhesus monkey
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