| globular cell | Laine and Axelrad (LA) | These cells are found scattered in the different folia of the vermis, thus appearing to be distributed throughout the cerebellar cortex....The soma nearly always (14/15) lies in the upper third of the granular layer (Figs. 1, 2 and 4) or inside the PC layer. In all globular cells the soma has a multipolar morphology, with radiating dendrites, a pattern highly reminiscent of that of Golgi cells. The pericaryon is more or less rounded, most often globular, and has a mean great axis of 14.5 micrometers and a mean somatic area of 129 micrometers2 . Nevertheless, some somata are more or less triangular or polyedric. The outstanding majority of our neurons (12/15) have no more than three to four dendritic trunks (see Table 1) and, frequently, the neurites draw a cross-like figure: three thick dendrites extend at right angles from the three cardinal points of the soma, whilst the axon emerges at the fourth (Figs. 1, 2 and 4). ...The axon usually originates with a rather thick initial segment, directly from the pericaryon (13/15) or from a proximal dendrite. The axonal stem can either directly ascend into the molecular layer where it ramifies (Figs. 1, 4), or it may first engage in a descending course (Fig. 2), giving off several thick collaterals which, after making a hairpin turn, re-ascend towards the molecular layer in which they branch. Before reaching the molecular layer, these collaterals usually give off short beaded fibers ending inside the granular layer (Figs. 1, 2)....The axonal arborization in the molecular layer is quite intricate with rather profuse ramified branches. These fibers have a more or less homogeneous diameter, in the order of 1 micrometer, and exhibit numerous beaded swellings. They are mainly distributed in the inferior two thirds of the layer (Figs. 1 and 2) but, in some cases, may span the entire height of the molecular layer, reaching the pia mater (Fig. 4). ...five of these cells exhibit an axonal collateral which runs for long distances in the supraganglionic plexus, just above the apexes of PC somata. These collaterals follow a transverse direction, parallel to the great axis of the folium, i.e. exactly in the same direction as the parallel fibers. Such a collateral is identical to similar fibers found in Lugaro cell axons (Lugaro, 1894; Fox, 1959; Laine¤ and Axelrad, 1996). Moreover, as in the case of Lugaro cells, this type of long collateral does not seem present in all the globular neurons of our series. | includes | | We propose that these globular cells be considered as a subpopulation of an extended Lugaro cell class, with whom they share a unique pattern of axonal projection, a molecular specification by calretinin and an important afferentation by recurrent collaterals of PC axons. | Laine J. & Axelrad H. | Mihail Bota |
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