ISSN:
1432-1106
Keywords:
Cerebellar nuclei
;
Synaptic ultrastructure
;
Cat
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The synaptic organization of the cerebellar deep nuclei in the cat has been analysed with the Golgi technique and the electron microscope. The Golgi picture is qualitatively very similar in the four nuclei. Both thick and thin fibers, with the latter being more numerous, contribute to the formation of pericellular nests around large neurons, where a large amount of boutons “en passant” can be observed. The electron microscopic study corroborates these observations since the cell surface of large neurons is mostly covered by axon terminals, while smaller neurons receive very few axo-somatic synapses. According to their size and shape three types of axon terminals have been encountered synapsing on large neurons: medium-sized, large slender and climbing-like boutons. The two last types only represent less than 13% of the total amount of axon terminals, and they are considered as synaptic boutons arising from different sources. The medium-sized boutons must represent a mixed population. A majority of these boutons contain rounded vesicles, while some, in a variable proportion from one animal to another, contain flattened or pleomorphic vesicles. The morphological features of “active” zones present in medium-sized boutons are not related to the shape of the vesicular population. This lack of association between vesicular shape and a specific pattern of “active” zones has been discussed. In the neuropil, large and smaller dendritic profiles have their surface mostly covered by axon terminals. These boutons are morphologically of the same three types described in axo-somatic position. Synapses on axon hillocks and on the initial segments of axons of large neurons are frequently observed, the presynaptic element being always a medium-sized bouton. However, axo-axonic serial synapses are only a very rare observation. In all the normal cats used in this study, axons and axon terminals containing atypical organelles, mostly originated from the smooth endoplasmic reticulum and mitochondria, have been observed. They probably represent aspects of a degenerative process of axon terminals reflecting a continuous remodeling of synaptic connections, as has been suggested by Sotelo and Palay (1971).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00233433
