A Golgi study of the lateral reticular nucleus in the rat.

The organization of the lateral reticular nucleus (LRN) of the rat was investigated by using the Golgi technique. Golgi-Cox preparations revealed neurons with shapes similar to those observed in Nissl-stained preparations. Fusiform cells possess rectilinear dendrites with secondary dendrites which are longer than the parent stem. The remaining cell types have short dendrites which branch for three or four generations and follow a tortuous course. These two types of neurons are similar to the isodendritic and allodendritic neurons which have been reported in the reticular formation. The neurons throughout the LRN form cell clusters. In Golgi preparations five to ten cells are seen in each cluster but counterstaining reveals that the clusters are made up of many more cells than the Golgi preparations suggest. Many cells lie in close apposition and the dendrites of the cells in each cluster intertwine to form dendritic plexuses. Dendritic input from both neighbouring and distant cell clusters also contributes to the plexus formations within each cell cluster. Under high magnification, the dendrites show irregularities in their contours, including warty excrescenses, bumps and an array of spines, some of which are pedunculated. The appendages are confined primarily to distal portions of the dendrites, with few spines observed on the somata and proximal dendrites. Varicosed dendrites are also in common occurrence throughout the nucleus.