Distribution of Bergmann glial somata and processes: implications for function.

We have used immunocytochemistry for glial fibrillary adidic protein and glutamine synthetase to selectively label Bergmann glia in the adult rat cerebellum. From measurements of radial, tangential and en face sections we provide new data on the distribution and disposition of these glial cells. Specifically, Bergmann glia were found to have a mean areal packing density of 8,269 somata/mm2, their radial processes are packed at a mean density of 39,000/mm2, and their endfeet at the pial surface have a mean density of 19,973/mm2. Each Bergmann glial cell ist "responsible" for the equivalent of a column of cerebellar cortex having a base of 11 microns x 11 microns, a height of 170 microns, and a volume of 20,559 microns3. There are 8.1 Bergmann glia for each Purkinje cell, and each glial cell ensheaths between 2,142 and 6,358 Purkinje cell synapses. We use these data to offer insights on the roles of Bergmann glia during development and in the adult brain.