Nucleus raphe dorsalis: a morphometric Golgi study in rats of three age groups.

Using Rapid Golgi and Nissl techniques, three major cell types: fusiform, multipolar and ovoid-shaped were identified in the nucleus raphe dorsalis of male rats at 30, 90, and 220 days of age. We have described the orientation and dendritic architecture of raphe cells as to type and the relationships of these cells to blood vessels and surrounding structures. For each cell type, the origin of the axon is characteristic. One hundred neurons per age group were measured at their maximal linear extent and the number of spines on the somal surface was counted. Dendritic number, linear extent, diameter and the number of spines along a 50 micron segment near the mid-point of dendritic length in an equal number of primary and secondary dendrites were quantified in each age group. The most striking age-related changes in the multipolar and ovoid-shaped cells were dendritic number, diameter and spine number as well as the number of perisomatic spines. The fusiform cells showed the least age-related changes. In general, the nucleus raphe dorsalis is organized as a reticular nucleus with neurons having few, straight and poorly ramified dendrites.