A Golgi study on the inferior olivary nucleus in the red sting ray, Dasyatis akajei

The intranuclear organization of the inferior olivary nucleus (ION) was studied in the red sting ray, using the rapid Golgi method. The ION neurons had polygonal, triangular or spindle cell bodies which generated 3-5 primary dendrites. These dendrites were relatively straight, sparsely spinous, and distributed mainly within the ION. The axons of the ION neurons extended medially and joined fiber bundles which ran transversely in the ION. Three groups of olivary afferents were distinguished: fibers derived from the tegmental area travelled ventrally and ended totally in the ION, composing a dense fiber plexus; collaterals of fibers which extended in a longitudinal direction in and around the ION distributed mainly in the lateral portion of the ION; and collaterals of fibers which ran transversely in the ION also ended in the ION. Some fibers from these 3 afferent groups converged to form pericellular baskets. Thus, the fundamental organization of the ION in the red sting ray was similar to that of the ION in mammals.