Quantitative electron microscopical observations have been made on the afferent synaptology of neurones in laminae V and VII of the cervical spinal cord of the cat. Both laminae contain large bouton-covered polydendritic neurones of the type seen in the brainstem reticular formation. Each lamina contains two other categories of neurone. One of these, in lamina V, is peculiar in having a very high proportion of afferent boutons filled with dense-core vesicles; similar neurones exist in lamina VII, but their presynaptic afferents do not contain unusual quantities of dense-core vesicles. The third type of neurone in laminae V and VII seems to be identical with an oligodendritic neurone type found in the brainstem reticular formation and parafascicular-centromedian complex.
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