MORPHOLOGY AND DISTRIBUTION OF MICROGLIAL CELLS IN THE YOUNG AND ADULT-MOUSE CEREBELLUM

The morphology and distribution of microglial cells were studied in th e normal cerebellum of young and adult mice using the histochemical de monstration of nucleoside diphosphatase as a specific microglial marke r. Our results showed that microglial cells were present in all cerebe llar lobules of both young and adult mice, but their distribution and morphology were not homogeneous throughout the cerebellum. Heterogenei ty in microglial cell distribution was exclusively related to their lo cation in the different histological layers, and no significant differ ences were found either between the different cerebellar lobules or be tween young and adult mice. Microglial density was higher in the cereb ellar nuclei than in the cortex; within the cortex, the molecular laye r was less densely populated by microglial cells than the granular lay er and the white matter. The morphological study revealed that microgl ial cells were ramified in all cerebellar lobules of both young and ad ult mice but showed different sizes and ramification patterns as a fun ction of their specific location in the different histological layers. Several typologies of microglial cells were described on the basis of observations in both horizontal and coronal sections. The specific la yer-related pattern of microglial distribution and morphology in mouse cerebellum strongly suggests a physical and functional adaptation of these cells to the characteristics of their microenvironment. (C) 1995 Wiley-Liss, Inc.