Unbiased stereological quantification of unmyelinated fibers in the rat brain white matter

We applied unbiased stereological principles to estimate the volume of white matter and the total volume and length of the unmyelinated fibers in the white matter of the rat brain. The mean volume of the rat brain white matter was 119 mm(3). The mean total length and the mean total volume of the unmyelinated fibers in the white matter were 323 km and 35 mm(3), respectively. The described method provides a useful tool for future quantitative studies of changes in the unmyelinated fibers of white matter in various experimental conditions and in various neurodegenerative diseases.