Purkinje cell layer

Ikai et al. (1992) reported that the VTA sends projections to the rat cerebellar cortex and deep cerebellar nuclei bilaterally, with a slight contralateral predominance. In this study, dopaminergic efferents of the A10 cell group were reported to reach mainly the granule cell layer of the cerebellar cortex in the lateral portion of the hemispheres, with additional input to the Purkinje cell layer, but sparing the molecular layer. The deep cerebellar nuclei, and in particular the lateral nucleus, were instead found to receive inputs from nondopaminergic cells of the VTA, reciprocating projections to the VTA bilaterally and with a contralateral predominance. 

In the monkey cerebellar cortex, Melchitzky and Lewis (2000) have recently described a dopaminergic innervation that matched the rat data in terms of laminar distribution (reaching mainly the granule cell layer and arborizing densely in the subjacent Purkinje cell layer), but was confined to certain lobules of the cerebellar vermis. 

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 nAChR subunit immunochemistry in the cerebellar cortex. nAChR (A and C) a4 and (B and D) a7 subunits in (C and D) autistic compared to (A and B) control. M, molecular layer p, Purkinje cell layer g, granule cell layer... 

The axon of the Purkinje cell is myelinated (Fig. 9) and gives rise to recurrent collaterals (Bishop, 1982, 1988 Bishop and O Donoghue, 1986 Bishop et al., 1987 O Donoghue and Bishop, 1990). The collaterals form a plexus of beaded axons, mainly at the level of the Purkinje cell layer (Fig. 8a and b). They terminate on neighbouring... 

Fig. 9. Purkinje cell in sagittal section. Haggqvist stain. A. The small, densely stained nuclei in the Purkinje cell layer belong to the Bergmann glial cells. B. Initial segment of Purkinje cell myelinated axon (A) surrounded by pinceau of terminal basket cell axons. Abbreviations A = Purkinje cell axon B = Bergmann glial fiber D = Purkinje cell dendrite. Bar = 25 g.m.

Several other neuronal cell types have been identified in the cerebellar cortex. The Lugaro cell is a relatively rare fusiform neuron, located just below the Purkinje eell layer (Lugaro, 1894 Fox, 1959 Palay and Chan-Palay, 1974). Its dendrites streteh out along the boundary of the granular and the Purkinje cell layer, the destination of its axon is not known. Lugaro cells can be discriminated from Golgi cells immunocytochemically with specific antibodies (Section 3.6.2., Fig. 67). 

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. 37. Expression of phosphorylated neurofilament localization in normal human cerebellar cortex (A) and in Friedreich s disease (B). Note the strong positivity of the white matter and the molecular layers in a case of Friedreich s ataxia. No expression was found in the normal folium that was NissI counterstained to demonstrate the granular and Purkinje cell layer. M = molecular layer, P = Purkinje cell layer, G = granular layer, F = fiber layer. Marani, unpublished.

Fig. 50. Distribution of GluR5 (A), GluR6 (B), GluR7 (C), KA-1 (D), KA-2 (E) of subunits in RNAs of high-affinity kainate receptor mRNAs in coronal sections at level of the cerebellum of the rat. Gr, granular layer LC, locus coeruleus Mol, molecular layer P, Purkinje cell layer Po, pontine nuclei. Scale bars 2.3 mm. Wisden and Seeburg (1993).

Fig. 69. A. Monoclonal antibody Rat-302 recognizes a subset of neurons, later identified as unipolar brush cells, restricted to the granular layer of the flocculus and the vermis of rat cerebellum (arrows), whereas in other areas of the cerebellum no positive cells are found. B. In contrast, antibody Rat-303 recognizes Golgi-II cells in the granular layer (g) in the entire cerebellum. C. Rat-302 also recognizes Purkinje cells outside the caudal vermis and the flocculus. D. Rat-302 positive cells in the vermis. E and F. Unipolar brush cells recognized by Rat-302 have a round cell body and short dendrites ending in a spray of appendages (arrows), g, granular layer m, molecular layer p, Purkinje cell layer. Scale bars 500 fim in A and B, 50 /rm in C and D. 10 /rm in E and F. Hockfield (1987).

Fig. 70. Bright-field (A) and dark-field (B) photomicrographs of a cerebellar folium of rat cerebellum labelled with [ HJmuscimol to demonstrate the GABA receptors. Note the clustering of grains over the area corresponding to the glomeruli of the granule cell layer and the low level of autoradiographic grains over the molecular layer (m) and the Purkinje cell layer (arrows). W, white matter. Bar = 100 /im. Palacios et al. (1981a).

In view of the findings that 5HTig mRNA levels are relatively high in Purkinje cells, whereas receptor binding is low in the molecular and Purkinje cell layers, but relatively high in the deep nuclei, one is tempted to speculate that the 5HT,b receptor is localized presynaptically on Purkinje cell axon terminals. The ultrastructural localization of the 5HTib receptors remains, however, to be determined. 

Fig.78. A. x28 and B. x42 power photomicrographs of autoradiographs of iodocyanopindol ( ICYP) binding to adrenergic beta receptors in rat cerebellar cortex illustrating the high density of silver grains in the molecular layer and patches of increased receptor density over the Purkinje cell layer, m, molecular layer g, granule cell layer. (C) shows the patches at x 40 magnification with dark-field illumination. Sutin and Minneman (1985).

Fig. 79. Photomicrograph of camera lucida drawing (inset) of anterogradely labelled axons and terminal boutons in the crus I ansiform lobule of rat cerebellum after cholera toxin (b fragment) injection into the contralateral ventral tegmental area. Arrows point to rosettes characteristic of mossy fiber endings in the granular layer (G). P, Purkinje cell layer WM, white matter. Scale bar = 40 ixm. Ikai et al. (1992).

Fig. 82. A. Semidiagrammatic representation showing the correlation between the patterns of individually wheat germ agglutinin (WGA)-HRP labelled hypothalamo-cerebellar fibers and the diffuse patterns seen just above and below the Purkinje cell layer. B. Darkfield microphotograph of the termination of WGA-HRP-labelled hypothalamo-cerebellar fibers. Note the clusters of label just above (solid arrows) and below (open arrows) the Purkinje cell layer. GL, granular layer ML, molecular layer. Squirrel monkey. Scale bar = 75 fim for B. Haines et al. (1986)...

Fig. 85. A. Drawing displaying the distribution of mossy rosettes (dots) immunoreactive to monoclonal choline-acetyltransferase (ChAT) antibody. The section (40 fim thick) was cut sagittally through the middle vermis of rat cerebellum. A considerable number of immunoreactive mossy terminals are observed in lobules I through IXab, although they are much fewer than in lobules IXc and X. Calibration bar = 1 mm. B. Drawing of part of lobule IXab shows the overall distribution of immunoreactive fibers. Arrows indicate mossy fibers with glomerular rosettes. Small and large arrowheads point to some varicose fibers distributing in or near the Purkinje cell layer (PCL) and in the molecular layer (ML), respectively. The ML fibers are most frequently observed in this lobule and tend to be restricted to the inner half of the layer. Calibration bar = 200 jum. Ojima et al. (1989).

Fig. 190. Distribution of CRF and CGRP-immunoreactive climbing fibers in P7 mouse cerebellum (A-C) and in neurons of the inferior olive (D-F). CRF-immunoreactive climbing fibers and neurons are indicated by dots, CGRP-immunoreactive climbing fibers and neurons by open circles, a, b and c = subnuclei a, b and c of the medial accessory olive beta -i- group beta Cl, C2 = Crus I and II DAO = dorsal accessory olive dc = dorsal cap EGL.ML = external granular layer and molecular layer F = flocculus IGL = internal granular layer PF = paraflocculus MAO = medial accessory olive PO = principal olive PL = Purkinje cell layer. Redrawn from Yamano and Tohyama (1993).

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