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Quantitative electron microscopy on the injured hypoglossal nucleus in the rat

  • Published:
Journal of Neurocytology

Summary

The hypoglossal nuclei of adult male rats which had received left hypoglossal axotomies, were studied quantitatively by making area measurements of structures on twenty electron micrographs per hypoglossal nucleus. Boutons and dendrites were analysed in further detail by counting and measuring profiles, counting synaptic thickenings per profile, and counting degenerating profiles. Results of light microscopy were confirmed and extended. In injured nuclei, microglia increased from 2 days to 2 weeks after axotomy, wrapping around neuron perikarya and parts of the dendrites between boutons and their post-synaptic sites. As microglia diminished after 2 weeks, astrocyte processes increased and replaced them, reaching peak growth at 5 weeks after axotomy. From 7 days to 5 weeks after axotomy there were fewer synaptic junctions. Neurons became stripped of boutons, but dendrites retained some. Dendrites shrank and some degenerated. Boutons shrank and decreased in numbers. At 10 and 12 weeks, all parameters returned to normal, by which time the hypoglossal nerve had reconnected with the tongue.

Possibly the chronological succession from boutons to microglial processes to astrocyte processes to boutons covering the neuron perikarya reflects changes in the neuronal glycocalyx during repair.

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Authors and Affiliations

  1. Department of Physiology, University Medical School, EH8 9AG, Teviot Place, Edinburgh

    B. E. H. Sumner & Fiona I. Sutherland

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  1. B. E. H. Sumner
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  2. Fiona I. Sutherland
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Sumner, B.E.H., Sutherland, F.I. Quantitative electron microscopy on the injured hypoglossal nucleus in the rat. J Neurocytol 2, 315–328 (1973). https://doi.org/10.1007/BF01104033

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  • DOI: https://doi.org/10.1007/BF01104033

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