title: Postnatal development of retrosplenial projections to the parahippocampal region of the rat.
abstract: The rat parahippocampal region (PHR) and retrosplenial cortex (RSC) are cortical areas important for spatial cognition. In PHR, head-direction cells are present before eye-opening, earliest detected in postnatal day (P)11 animals. Border cells have been recorded around eye-opening (P16), while grid cells do not obtain adult-like features until the fourth postnatal week. In view of these developmental time-lines, we aimed to explore when afferents originating in RSC arrive in PHR. To this end, we injected rats aged P0-P28 with anterograde tracers into RSC. First, we characterized the organization of RSC-PHR projections in postnatal rats and compared these results with data obtained in the adult. Second, we described the morphological development of axonal plexus in PHR. We conclude that the first arriving RSC-axons in PHR, present from P1 onwards, already show a topographical organization similar to that seen in adults, although the labeled plexus does not obtain adult-like densities until P12.
authors.affiliation: Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University for Science and Technology, Trondheim, Norway.
authors.forename: Jørgen
authors.initials: J
authors.lastname: Sugar
authors.affiliation: Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University for Science and Technology, Trondheim, Norway.
authors.forename: Menno P
authors.identifier: 0000-0003-0285-1637
authors.initials: MP
authors.lastname: Witter
mesh_terms: D000818:Animals; D018728:Entorhinal Cortex / Q000033:anatomy & histology / Q000254:growth & development*; D009024:Morphogenesis; D009434:Neural Pathways / Q000033:anatomy & histology / Q000254:growth & development*; D051381:Rats; D013997:Time Factors
keywords: Long Evans; cingulate cortex; entorhinal cortex; neural pathways; neuroscience; postrhinal cortex; pre-parasubiculum; rat