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Synaptic fine structure and the termination of corticospinal fibers in the lateral basal region of the cat spinal cord
Author(s) -
Hanaway Joseph,
Smith Jeanne M.
Publication year - 1979
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901830303
Subject(s) - spinal cord , biology , anatomy , degeneration (medical) , axon , corticospinal tract , synaptic vesicle , vesicle , neuroscience , pathology , medicine , magnetic resonance imaging , genetics , radiology , membrane , diffusion mri
Abstract The lateral basal region (LBR) of the spinal cord gray matter (Rexed's laminae IV‐VII) by physiologic and anatomic criteria is the major terminal zone for the corticospinal (CS) tract in the cat. The neurons in this area are medium‐sized with abundant spines on their dendrites. Axon terminals on the dendrites and somata of these neurons form synapses easily classified as asymmetric with spheroid vesicles and symmetric with flattened vesicles. There are rare exceptions to this. In a systematic count of terminals, 82% have spheroid and 18% flattened vesicles. The majority of all terminals are on dendrites (84.9%) and a minority on somata (14.1%). Less than 1% are axoaxonic. Degeneration of the corticospinal tract was produced by transecting one hemisphere of our experimental cats. Its termination in the lower cervical cord was studied for 17 hours to 7 days after surgery. Vesicle depletion and clumping and dense polymembranous inclusions were the most common forms of degeneration. Filamentous proliferation in the terminals was also prominent; dark degeneration, however, was infrequent. The percent of degenerating CS terminals in the LBR was the following: 17 hours – 2.2%, 36 hours – 4.19%, 2 days – 10.3%, 3 days – 8.4%, 4 days – 6.9%, 7 days – 10.25%; 84.8% of degenerating CS terminals were axodendritic and 15.2% axosomatic.