Morphometric analysis of developing neuronal geometry in the dorsal cochlear nucleus of the hamster.

Since the shape of a cell's dendritic field and the distribution of its input determine the information that a cell receives and transmits, it is important to ascertain how the spatial relations between axonal arbors and dendritic fields develop. This study investigates the development of the dendritic fields of fusiform cells in the dorsal cochlear nucleus. Golgi-impregnated cells from postnatal day 10, 15, 25, 45 and 60+ hamsters were reconstructed. The computerized morphometric system used analyzed cells in the plane of section and also allowed rotation to and analysis in other specified planes, such as that parallel to the terminal arbors of the cochlear nerve fibers. The results suggest that the apical dendritic fields are oriented parallel to the axis of cochleotopic organization and that this orientation develops gradually after birth. Dendritic growth is the result of addition of new dendritic branches. The angles between branches also change and were analyzed by viewing the dendritic fields in different planes. This revealed that some preferential expansion of the apical dendritic field in the plane parallel to the cochlear projection planes is the result of increased angles between branches in that plane. Thus, dendritic growth via the addition of branches and the 'fanning-out' of existing branches underlie the development of oriented dendritic fields.