Cognitive, Behavioral, and Systems NeuroscienceResearch PaperSpatial characterization of the motor neuron columns supplying the rat forelimb
Highlights
▶In this study we provided a map of the motor end plates for 11 rat forelimb muscles. ▶We characterized the spatial distribution of the motor columns supplying these muscles. ▶The length and the overlap between some motor neuron columns is greater than previously described. ▶The upper cervical enlargement contains more motor neuron columns than previously reported. ▶This provides a greater understanding of the organization of the motor columns for the rat forelimb.
Section snippets
Animals
All experimental procedures complied with the Animal Care and Ethics Committee of the University of New South Wales and were performed in accordance with the National Health and Medical Research Council of Australia regulations for animal experimentation. A total of 27 adult female hooded rats (Rattus norvegicus; Long-Evans) (Monash University, Victoria, Australia) weighing approximately 250 g at the time of surgery were used in this study. The rats were housed in groups of four in an animal
Localization of the motor end plates in the rat forelimb
The location of the motor end plates in each muscle under investigation is shown in Fig. 1, Fig. 2. Fig. 1 is a photograph of the lateral view of a rat forelimb processed with an aceytlcholinesterase reaction that reveals the motor end plate regions. On this photograph, the motor end plates appear as black speckles aligned on the brown muscle fibres. Moreover, Fig. 1 also shows the direction of the muscle fibres in situ. Analysis of the lateral, ventral, and dorsal views of the forelimbs used
Discussion
The aim of this research was to characterize the details of the spatial organization of the columns of motor neurons that supply the musculature of the rat forelimb. Particular attention was given to identify the degree of overlap between these motor columns that lie in the cervical segments of the spinal cord and that has been incidentally reported (McKenna et al., 2000). Special emphasis was also placed on the number of motor neuron columns spanning the cervical enlargement. The results of
Conclusion
This anatomical investigation supports previous observations that, although discrete, some of the motor neuron columns lying in the cervical aspect of the rat spinal cord are inter-digitized. The length of these columns, and hence the overlap between them, appears to be greater than previously reported, particularly within the uppermost segments of the cervical enlargement. This map constitutes a valuable guide for the selection of appropriate muscle(s) for the delivery of therapeutic genes
Acknowledgments
The research was supported by the Christopher and Dana Reeve Foundation (Renée Morris) and by a University of New South Wales Faculty of Medicine Research Grant (Renée Morris).
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