Cerebellum molecular layer

Regional distribution studies indicate that the highest density of kainate receptor occurs in the stratum lucidum of the hippocampus (mossy fiber system) and in the inner and outer layers of the neocortex. The highest density of NMDA receptors is found in the hippocampus, stratum radiatum, and in the striatum, thalamus, and cerebral cortex. The distribution of AMPA receptors is similar to that of NMDA receptors, but in the cerebellum AMPA receptors predominate in the molecular layer... 

Figure 16-6. Section of rat brain and cerebellum. Note the presence of Purkinje cells lining the granular and molecular layer and the Purkinje cells with dendrites.

Except for the hilar region of the islands of Calleja, the lateral habenula and the Purkinje cells of cerebellum, D3 mRNA matched the distribution of the receptor (Diaz et al., 2000). In the archicerebellum, in fact, D3 mRNA was found to be expressed in the Purkinje cells of lobules 9 and 10, whereas D3 binding sites were contained in the molecular layer surrounding the Purkinje cell layer of lobule 10 and in the ventral molecular layer of lobule 9 (Levant et al., 1993 Diaz et al., 1995). 

Fig. 3. Distribution of 81 (A) and 82 (B) subunit mRNA in the adult rat brain (X-ray film autoradiographs, horizontal sections) (C), localization of 82 mRNA in cerebellar Purkinje cells (emulsion autoradiograph). Cb, cerebellum Ctx, neocortex Gr, granule cells H, hippocampus Mol, molecular layer P, Purkinje cells arrowheads mark labelled Purkinje cells. Scale bar in B, 3.5 mm scale bar in C, 28 pm (Lomeli et al., 1993).

The highest concentrations of GLAST are seen in the molecular layer of the cerebellum, the Bergmann glia in particular (Lehre et ah, 1995). Compared to the cerebellum, the concentrations of GLAST protein in bulbus olfactorius, hippocampus, cerebral cortex and thalamus are 49, 35, 33 and 22%, respectively (Lehre et ah, 1995 Lehre and Danbolt, 1998 0. Haugeto and N.C. Danbolt, unpublished). 

Fig. 7. Granule cells and parallel fibers after an injection of biocytin in lobule X of the cerebellum of the rat. A. Biocytin labelled granule cell. B. Golgi-impregnated granule cells and parallel fibers in transverse section. Cajal (1911). C. biocytin injection site in granular layer and labelled parallel fibers in molecular layer. D. bifurcation site of labelled parallel fibers. E. labelled varicose parallel fibers. Abbreviations A molecular layer B granular layer C white matter a granule cell axon b bifurcation of granule cell axon d Purkinje cell f Purkinje cell axon g granular layer I injection site m molecular layer. Bars in A = 12 /tm, in C = 500 nva, in D and E = 50 //m. Courtesy of Dr. T.J.H. Ruigrok.

Purkinje cells. The recurrent collaterals extend into the molecular layer where they contact basket cells (O Donoghue et al., 1989). The whole collateral arborization is oriented perpendicular to the long axis of the folia, i.e. in the same plane as the dendritic tree of the Purkinje cell. In the cat it measures 300-700 //m in the sagittal and 100 00 m in the transverse direction (Bishop, 1988). The width of the arborization and its penetration in the molecular and granular layers varies for different parts of the cerebellum. Recurrent collaterals of Purkinje cell axons are constituents of the infra- and supraganglionic plexus. The main Purkinje cell axon enters and traverses the white matter to terminate on cells of the cerebellar or the vestibular nuclei. 

Fig. 12. Purkinje cells from the cerebellum of, from left to right, birds Callus domesticus, Feirabend, 1983) mammals (cat, Cajal, 1911) and fish (Gnathonemus petersii, Nieuwenhuys, 1969). Note different length, orientation and position in the molecular layer of the spiny dendritic branchlets.

Fig. 14. Phaseolus vulgaris lectin-labelled climbing fibers of rat cerebellum. A, Sagittal section. B. Coronal section. Abbreviations G = granular layer M = molecular layer P = Zebrin- labelled Purkinje cells. Bar = 100 jum. Courtesy of Dr. T.J.H. Ruigrok.

Fig. 25. Localization of the P400-specific mRNA by in situ hybridization, a. Autoradiograph of a sagittal section of mouse cerebellum, b. Higher magnification of a. ML, molecular layer PL, Purkinje cell layer GL, granular layer. Furuichi et al. (1989).

Fig. 27. Immunofluorescence localization of the cerebellar Ca -ATPase in a transverse cryosection of adult chicken cerebellum. CaS/Cl-IgG localizes the Ca -ATPase to the Purkinje cell bodies in the Purkinje layer (b), and the dendritic trees in the molecular layer (a). Very faint immunofluorescence was detected in the granule cell layer (c). Bar 50 m. Kaprielian et al. (1989).

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