Summary
The electron microscopical changes occurring in the pontine nuclei following unilateral lesions of the primary sensorimotor cortex have been studied in 7 cats with a survival time from 2–23 days. A description is also given of the fine structure of the pontine regions in receipt of the fibres. These regions are shown in Fig. 1.
The study shows that the boutons are practically only in synaptic contact with dendrites. The bouton density on these is only 16%. The boutons are of the en passage and terminal type, with the latter as the most common (Figs. 4a-e). The synaptic vesicles are rounded or elongated. The formaldehyde fixed material had 17.8% boutons with vesicles of the elongated type; the material fixed with a mixture of formaldehyde and glutaraldehyde had only 11.5% of such boutons.
The degenerating boutons show the dark type of reaction and the majority of the corticopontine fibres are of the type shown in Figs. 4d and 4e. Astrocytes and microglial cells participate in the removal of degenerating boutons and terminal fibres. Degenerating boutons are present even at the 23 day stage and some have apparently only started to degenerate.
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On leave of absence from the Max-Planck-Institut für Psychiatrie, Munich. Germany.
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HollÄnder, H., Brodal, P. & Walberg, F. Electronmicroscopic observations on the structure of the pontine nuclei and the mode of termination of the corticopontine fibres an experimental study in the cat. Exp Brain Res 7, 95–110 (1969). https://doi.org/10.1007/BF00235436
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DOI: https://doi.org/10.1007/BF00235436