Mossy fiber rosettes

The actual strength of the convergence of individual mossy fibers to Purkinje cells depends on the distribution of their mossy fiber rosettes. Electrophysiological studies of Bower and Woolston (1983) in the rat demonstrated that Purkinje cells are most responsive to mossy fiber input that reaches the granule cells located immediately below them. Llinas (1982) explained this strong radial connectivity by the greater number of... 

Summarizing it appears that the cellular and regional distribution of muscarine receptors in the cerebellum is different between different species. Golgi cells and subpopulations of mossy fibers seem to express muscarine receptors most constantly. An interesting aspect about the presence of muscarine receptors in parallel fibers in rat and rabbit, is that the lobular distribution of m2-containing parallel fibers, is the same as that of ChAT-positive mossy fiber rosettes (see above). This raises the possibility that muscarine m2 receptor are specifically expressed by those granule cells that are innervated by cholinergic mossy fibers. If this proves to be true, this would imply that there... 

Fig. 199. Primary and secondary vestibulocerebellar mossy fiber projections in the rabbit, determined with antegrade axonal transport of [3H]leucine and WGA-HRP. Upper panels sagittal sections lower panels transverse sections through the caudal vermis. K196 ipsilateral distribution of fibers of the vestibular nerve. Gerrits et al., (1989) C2098 bilateral distribution of fibers from the medial vestibular nucleus (MV) K82 bilateral distributions of fibers from the superior vestibular nucleus (SV Thunnissen et al., 1989). Dense termination in the sagittal sections is indicated with heavy hatching, scattered labelled mossy fiber rosettes with light hatching and dots. Note similarity in the distribution of primary and secondary vestibulocerebellar projections.

P2- (i.e. the B zone) extending into P3+ (Fig. 207). Matsushita et al. (1991), who mapped fibers from the cervical cord in Zebrin-I stained sections of rat cerebellum found less correspondence of the concentrations of rosettes with the borders of the im-munoreactive Purkinje cell zones. Ji and Hawkes (1994) showed that cuneocerebellar mossy fiber terminals are located between the concentrations of lumbar spinocerebellar mossy fiber rosettes in P1+, PI - and P2- of lobules II and III of the rat cerebellum (Fig. 207). A close correspondence between multiple patches of mossy fibers with vibrissal receptive fields and the Zebrin-negative P1-, P2- and P3- zones of lobule IX of the rat cerebellum, was observed by Chockkan and Hawkes (1994). 

It is generally assumed that the distribution of mossy fiber rosettes over the cerebellar cortex is uniform and that all mossy fibers use glutamate as a neurotransmitter (Raymond et al., 1984 Beitz et al., 1986 Clements et al., 1986, 1987 Kaneko et al., 1987,... 

ChAT-positive mossy fiber rosettes were most numerous in the caudal vermis of the rat, the rosettes were large in X and smaller in ventral lobule IX and the lobules... 

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