Item – Theses Canada

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OCLC number
27680781
Author
Gordon, David Christopher,1962-
Title
Topographic relationships between motoneurons in the cat spinal cord demonstrated by retrograde multiple-labelling techniques.
Degree
Ph. D. -- Queen's University at Kingston, 1990
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1991.
Description
3 microfiches.
Notes
University Microfilms order no. UMI00281730.
Includes bibliographical references.
Abstract
A combination of retrograde labelling methods was used to examine the topographical organization of motoneurons at three different segmental levels of the cat spinal cord. In an initial study the compatibility of the tracers horseradish peroxidase, fast or true blue, diamidino yellow and fluorogold was assessed by applying the different tracers concurrently to separate cut branches of hindlimb and neck muscle nerves. On the basis of these initial observations fast blue, fluorogold and horseradish peroxidase were chosen for use in three subsequent studies of motoneuronal distribution. In the first study, individual primary branches of the phrenic motor nerve were exposed to different tracers. Motoneurons supplying different territories in the diaphragm by way of these nerve branches were intermixed extensively throughout most of the phrenic nucleus. However, motoneurons innervating the sternal region was distributed more densely in the rostral part of the phrenic nucleus than motoneurons supplying other parts of the diaphragm. In the second study, the organization of motor nuclei supplying the hindlimb muscles sartorius and tensor fasciae latae was studied by applying different tracers to nerve branches serving muscle regions that were reported to differ in their biomechanical actions and electromyographic activity. In each of these motor nuclei the motoneurons supplying different parts of the muscle overlapped extensively. In tensor fasciae latae, no statistically detectable differences could be recognized between different subpopulations of neurons. However in sartorius, motoneurons supplying medial regions were distributed more densely in the rostral part of the sartorius motor nucleus. This gradient was modest and showed substantial cat-to-cat variation. In the final study multiple labelling methods were used to examine the topographical organization of motoneurons supplying the suboccipital muscles, rectus capitis posterior and obliquus capitis inferior, the intervertebral muscles, spinalis dorsi and semispinalis cervicis, and the long dorsal muscle, biventer cervicis. Motoneurons supplying suboccipital muscles were intermingled in the rostral two cervical segments. Motoneurons supplying the intervertebral muscles occupied overlapping territories caudal to C3 in a region medial to the column of labelled motoneurons supplying biventer cervicis. The results of these studies suggest that the peripheral neuromuscular compartments seen in complex muscles do not always have similar anatomical divisions centrally within their motor nuclei even when these compartments are capable of independent recruitment. The absence of topographical relationships in some muscles requires us to postulate the existence of other mechanisms governing the specificity neural connections.
ISBN
0315615818
9780315615816