Reelin immunoreactivity in the adult neocortex: a comparative study in rodents, carnivores, and non-human primates

Recent evidence indicates that, in addition to playing a crucial role in early cortical development, intercellular signaling mediated by the protein Reelin may be widely active in the adult neocortex. The extent of Reelin distribution and its functional role in the adult are not clear yet. Here, we have examined Reelin immunoreactivity in the neocortex of an adult rodent (rat, Rattus norvegicus), a carnivore (ferret, Mustela putorius), and a primate (macaque monkeys Macaca nemestrina, Macaca mulatta) at the optic microscope level. Our data show that the neocortex of all three species contains several morphologically distinct populations of interneurons whose perikaryon and proximal dendritic processes are heavily immunoreactive for Reelin. The laminar distribution of these cells is species-specific. In addition, discrete reelin-immunoreactive pericellular structures are present in virtually all neocortical neurons of macaques.