UNBIASED STEREOLOGICAL ESTIMATION OF DIFFERENT CELL TYPES IN RAT CEREBRAL CORTEX

The total numbers of neurons, glial cells, and endothelial cells in rat cerebral cortex were estimated using unbiased stereological counting techniques and systematic sampling. The reference volume chosen was the entire neocortex, most of the allocortex and parts of claustrum using the rhinal fissure as the macroscopical anatomical landmark. These regions are referred to collectively as syncortex. A method has been devised for reducing problems associated with the uncertainties that arise when distinguishing between various types of cells. At the light microscopic level, using the detailed criteria described in this article, the total numbers of neurons, glial cells, and endothelial cells, respectively, were estimated for the entire syncortex as the product of the estimate of the volume of the syncortex, made with point counting techniques, and the estimates of the numerical density for each group of cells, made with optical disectors. In a sample of three brains, the mean total number of cells (neurons, glial and endothelial) in the syncortex of the rat brain is 128 x 106. This number is made up of 47% neurons, 24% glial cells, 17% endothelial cells, and 11% uncertain cell types (probably mostly glial cells).