Unbiased estimates of number and size of rat dorsal root ganglion cells in studies of structure and cell survival.

For quantitative studies of rat dorsal root ganglion (DRG) in experimental models stereological principles offer a number of different techniques. The application, however, requires knowledge of the anatomy and cytology of the ganglion, considerations of sampling and choosing between the many estimators available. For number and volume estimates in thick glycolmethacrylate sections the optical fractionator and the vertical planar rotator technique in most cases provide sufficient efficiency and are simple to use. Classification of the neurons in the DRG into A- and B-cells is of value in experimental conditions where the two cell types can react differently. Studies on development and subclassification of neuronal DRG cells will gain from application of stereological methods, also. Until now the methods have mainly been applied in studies of axotomy and in a few intoxication models where the time course of cell loss and changes in perikarya volume are important parameters. Further quantitative studies providing better understanding of distribution and expression of neuropeptides, cytokines, apoptotic molecules etc. will provide insight for future therapeutic approaches in neurodegenerative disorders. The more demanding staining techniques require less restrictive embedding media, but unbiased principles are available for almost all the stereological techniques applied to tissue only deformed after sectioning.