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Spinal cord lamina V and lamina VII interneuronal projections to sympathetic preganglionic neurons
Author(s) -
Cabot J. B.,
Alessi V.,
Carroll J.,
Ligorio M.
Publication year - 1994
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.903470404
Subject(s) - spinal cord , anatomy , lamina , wheat germ agglutinin , biology , neuropil , superior cervical ganglion , lateral funiculus , lumbar spinal cord , neuroscience , central nervous system , lectin , biochemistry
This light and electron microscopic study sought to localize spinal cord interneurons that contribute to the normal and abnormal physiological regulation of spinal sympathetic preganglionic function. Sympathetic preganglionic neurons in caudal C8 through T4 of rat spinal cord were retrogradely labeled with wheat germ agglutinin (WGA) and/or cholera β subunit (CTβ) following injections into the superior cervical ganglion (SCG). With two exceptions, the observed locations of retrogradely VVGA‐ and CTβ‐labeled sympathetic preganglionic neurons were as expected from previous studies. The exceptions were restricted populations of cells in caudal C8 and rostral T1 spinal segments. These neurons were classified as ventrolateral (vlSPN) and ventromedial (vmSPN) sympathetic preganglionic neurons; their somata and dendrites encircled dorsolateral lamina IX motoneurons. Only WGA was transported transneuronally following the retrograde labeling of sympathetic preganglionic neurons. Transneuronally WGA‐labeled spinal interneurons were located principally in the reticulated division of lamina V and dorsolateral lamina VII. A strict segmental organization was observed. All transneuronally labeled interneurons were ipsilateral to, and coextensive with, retrogradely WGA‐labeled sympathetic preganglionic neurons. Electron microscopic observations suggested that retrograde transsynaptic passage of WGA occurred within the sympathetic preganglionic neuropil and showed further that similar classes of organelles were WGA immunoreactive in retrogradely labeled sympathetic preganglionic neurons and in transneuronally labeled lamina V and lamina VII neurons: (1) cisternae and vesicles at the trans face of the Golgi apparatus, (2) large endosomes/dense bodies, and (3) multivesicular bodies. The data are consistent with two hypotheses: (1) Somatic and visceral primary afferent inputs to thoracic spinal cord modify segmental sympathetic preganglionic function through activation of a disynaptic pathway involving lamina V and/or lamina VII interneurons, and (2) long‐loop propriospinal pathways access sympathetic preganglionic neurons through symmetrical, segmental interneuronal circuitry. © 1994 Wiley‐Liss, Inc.