Differential distribution of intermembranous particles in the plasmalemma of the migrating cerebellar granule cells.

The size and distribution of intramembraneous particles in 5 different plasmalemma domains of migrating cerebellar granule cells was studied by the freeze-fracture method. The quantitative analysis in 5-20-day-old rats reveals that the membrane of the leading tip of the descending process, the soma and vertical process that are associated with Bergmann glial fibers, have a significantly higher density of small (less than 11 nm diameter) intramembraneous protein particles than the horizontal processes and their growth cones which grow along previously generated parallel fibers. This regional difference in density of membrane associated particles may be related to the selective outgrowth of the two classes of granule cell neurites along glial and neuronal surfaces.