A METHOD FOR UNBIASED AND EFFICIENT ESTIMATION OF NUMBER AND MEAN VOLUME OF SPECIFIED NEURON SUBTYPES IN RAT DORSAL-ROOT GANGLION

By means of unbiased stereological principles and systematic sampling techniques, the number, the mean volume, and the distributions of neuron volumes of the A- and B-cells of the dorsal root ganglion have been estimated. The number of each neuron type was estimated from the product of the volume of the ganglion, obtained with the Cavalieri principle on serial sections of the ganglion, and the numerical density, obtained with optical disectors on the same sections. The mean volume of the cell bodies of each type was estimated by applying the nucleator technique to the neurons sampled with the optical disectors. The precision of the estimate in each animal was evaluated on the basis of the variation between animals. An optimal sampling scheme is described by which estimates of the total number, the mean volume, and the distribution of cell body volumes can be obtained in about 8 hours. In the right fifth lumbar dorsal root ganglion taken from four mature, male Wistar rats, the mean total number of neurons was found to be 17,900. Of these, 28% were A-cells, with a mean cell body volume of 53,400 mum3, and 70% were B-cells, with a mean cell body volume of 8,540 mum3. There was a considerable overlap between the volume distributions of the two cell types.