Development of neocortical circuitry: Histochemical localization of acetylcholinesterase in relation to the cell layers of rat somatosensory cortex

Abstract

Acetylcholineserase (AchE) was istochemically localized in neocorex cerebri of newborn to 1-week-old rats. At birth AchE-dependent staining is limited to scaerd somata (Cajal-Retzius cells) in the marginal zone and a few fibers and somata in primordial layer VI. By the end of the first week, neuronal elements are relatively well sained in pzrticular cell laminae, giving th appearance of three horizontal AchE-rich “bands” which alternate with AchE-poor laminae. The subpial band (layer I) is a narrow tangential zone of intensel saining fibers and scatered somata. The mid-corical band contains an AchE-positive fiber plexus (primordial layer IV) and numerous stained somata (pyramids of primordial layer V). In layer IV of the SmI region, intermittent foci of staining are noted which overlap the barels' distribution in the barrel field. The deep cortical band (bottom of primordial layer VI) consists of numerous stained somata (Marinotti cells). It is concluded that there is a laminar patern of acetylcholinesterase-dependent staining in postanatal rat somatosensory corex, and that the laminar pattern bears a consistent spatial relation both to the cell layers and to the depths of high synapse density in immature cortex.