Postnatal development of mitral cell perikaryon in the olfactory bulb of the rat. A light and ultrastructural study.

The differentiation of the mitral cell perikaryon in postnatal rat olfactory bulb was studied with the light and electron microscope. At birth the mitral cell was distinguishable and occupied a definitive position in the mitral cell layer. The cell contained a large oval nucleus surrounded by a thin rim of cytoplasm. Ribosomes, free and clustered, were scattered in the cell cytoplasm. Rough endoplasmic reticulum was relatively scarce. The Golgi complexes were made up of stacks of smooth-surfaced cisternae and associated vesicles. In certain cases the Golgi complexes projected into cellular processes. Mitochondria were present in all regions of the cytoplasm and contained well developed cristae. At the end of the first week, the mitral cell had developed significantly in size, and the cytoplasm contained well-developed rough endoplasmic reticulum. The Golgi complexes were made up of several stacks of smooth-surfaced cisternae with the association of vesicles and electron dense bodies. The apical dendrites of mitral cells at this period had increased significantly in length. Subsequently, during the second and third week, the rough endoplasmic reticulum and Golgi complexes became well developed. Associated with the Golgi complexes were electron dense lysosomal bodies. At three weeks and in older cells it was observed that dense lipofuschin granules increased significantly. It is suggested that the mitral cell matures and differentiates earlier than cells in the cerebral cortex.