The intraglandular submandibular ganglion of postnatal and adult rats. II. A morphometric and quantitative study.

A morphometric study was undertaken on the submandibular ganglion cells in rats of different ages. This showed a direct proportional increase with age in all the variables measured. Mean cross-sectional cell area showed the most dramatic growth, an increase of more than 5-fold between birth and young adulthood. Mean cell diameter and cell perimeter doubled over the same period. The growth of the nucleus, expressed as diameter, was slower when compared with that of the ganglion cells as a whole. The number of intraglandular ganglion cells remained relatively unchanged from birth to young adulthood, ranging from about 3000 to 5000 cells. They were mainly distributed at the hilar region of the submandibular salivary gland, contributing 1/2 to 2/3 of the total ganglion cell population. The second largest cell population was in the intralobular region, which made up about one-third of the population. The least populated region was in the connective tissue of the sublingual salivary gland, which contained only about 5-7% of the total cell number. Cell counts based on the fluorogold labelling method were generally lower than those made after haematoxylin and eosin staining. In the 2-d-old animals, counts of fluorogold-labelled cells were only about half the H & E counts. The discrepancy may be due to the thicker sections used in the fluorogold method, superimposition of cells leading to an underestimation of cell numbers. Nevertheless, the fluorogold labelling method provided rapid and reproducible results. Its main advantage is that the labelled ganglion cells emit a bright yellow fluorescence which is readily identified; the other is the simplicity of the procedure, as labelling of ganglion cells can be achieved by the intraperitoneal route.