A comparison of quantitative histological changes in different regions of the ageing mouse cerebellum.

The number of Purkinje cells per mm and the number of granule cells per mm3 were estimated in the lobus simplex of mice aged 6, 15, 22, 25, 28 and 31 months. The results were compared with similar estimations already carried out in the spinocerebellum and nodulus of the same cerebella. All regions showed a decrease of approximately 30% in Purkinje cell number between 6 and 31 months of age with the decrease occurring between 15 and 31 months. At each age examined the number of Purkinje cells per mm was similar in the spino- and pontocerebellum but significantly smaller in the nodulus. Granule cell density was identical in all parts of the cerebellum at all ages. Molecular layer thickness varied significantly with age in all cerebellar regions but this may be an artefactual variation. Granule layer thickness did not vary with age in either the nodulus or spinocerebellum but there was a significant variation in granule layer thickness, in the pontocerebellum due to a substantial decrease in thickness between 28 and 31 months of age. This might be the result of a loss of granule cells in this region which is not apparent in other parts of the cerebellum.