Pyramidal and nonpyramidal callosal cells in the striate cortex of the adult rat

The aim of this study has been to determine the neuronal types (pyramidal and nonpyramidal) within the rat's visual cortex, which project through the corpus callosum. To this end, the morphology and laminar distribution of callosal cells have been investigated by combining Diamidino Yellow retrograde tracing with intracellular injection of Lucifer Yellow in slightly fixed tissue slices. The visual callosal projection arises from pyramidal cells of diverse morphology in layers II to VIb, as well as from several modified pyramids located mainly in layers II, IV (star pyramids) and VIb (horizontal or inverted pyramids and related forms of spiny stellate cells). Our results indicate that in rat…