Differentiation of apical, basal and mixed dendrites of fusiform cells in the cochlear nucleus

Many studies suggest that the details of morphogenesis (e.g. the length and number of dendrites) are determined by factors extrinsic to the cell, while the basic form of the neuron (e.g. the shape of the soma and the placement of the primary dendritic trunks) is determined by intrinsic factors. The following study describes the development of the dendrites of fusiform cells in the dorsal cochlear nucleus of the hamster using Golgi-stained brains from hamsters of various ages. Two basic types of dendrites are described--apical and basal--which emanate from opposite ends of the cell body and differ in their morphology. A third type of dendrite that exits the cell laterally can create a deflection in the perimeter of the cell body altering its shape. The morphology of these dendrites is described and compared to the apical and basal dendrites. Segments of laterally extending dendrites that are near apical dendrites are qualitatively and quantitatively identical to apical dendrites (that is they branch frequently and are spine-laden) and the converse is true of the segments near basal dendrites. The results suggest that during development, whether a dendritic will be apical-like or basal-like is determined by the location of its distal segment. Thus, extrinsic factors influence the overall form of these neurons.