Developmental Profile, Morphology, and Synaptic Connectivity of Cajal-Retzius Cells in the Postnatal Mouse Hippocampus

Cereb Cortex. 2016 Feb;26(2):855-72. doi: 10.1093/cercor/bhv271. Epub 2015 Nov 18.

Abstract

Cajal-Retzius (CR) cells are early generated neurons, involved in the assembly of developing neocortical and hippocampal circuits. However, their roles in networks of the postnatal brain remain poorly understood. In order to get insights into these latter functions, we have studied their morphological and synaptic properties in the postnatal hippocampus of the CXCR4-EGFP mouse, where CR cells are easily identifiable. Our data indicate that CR cells are nonuniformly distributed along different subfields of the hippocampal formation, and that their postnatal decline is regulated in a region-specific manner. In fact, CR cells persist in distinct areas of fully mature animals. Subclasses of CR cells project and target either local (molecular layers) or distant regions [subicular complex and entorhinal cortex (EC)] of the hippocampal formation, but have similar firing patterns. Lastly, CR cells are biased toward targeting dendritic shafts compared with spines, and produce large-amplitude glutamatergic unitary postsynaptic potentials on γ-aminobutyric acid (GABA) containing interneurons. Taken together, our results suggest that CR cells are involved in a novel excitatory loop of the postnatal hippocampal formation, which potentially contributes to shaping the flow of information between the hippocampus, parahippocampal regions and entorhinal cortex, and to the low seizure threshold of these brain areas.

Keywords: CXCR4-EGFP mice; hippocampal Cajal–Retzius cells; light- and electron microscopy; patch-clamp recordings; synaptic connectivity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Animals
  • Animals, Newborn
  • Axons / metabolism
  • Axons / ultrastructure
  • Biophysics
  • Dendrites / metabolism
  • Dendrites / ultrastructure
  • Electric Stimulation
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Hippocampus / cytology*
  • Hippocampus / growth & development*
  • Image Processing, Computer-Assisted
  • In Vitro Techniques
  • Lysine / analogs & derivatives
  • Lysine / metabolism
  • Membrane Potentials / genetics
  • Membrane Potentials / physiology
  • Mice
  • Mice, Transgenic
  • Microscopy, Electron, Transmission
  • Models, Neurological
  • Neocortex / cytology*
  • Neocortex / growth & development*
  • Neurons / cytology*
  • Neurons / physiology
  • Patch-Clamp Techniques
  • Receptors, CXCR4 / genetics
  • Receptors, CXCR4 / metabolism
  • Synapses / physiology*
  • Synapses / ultrastructure
  • gamma-Aminobutyric Acid / metabolism

Substances

  • CXCR4 protein, mouse
  • Receptors, CXCR4
  • Green Fluorescent Proteins
  • gamma-Aminobutyric Acid
  • biocytin
  • Lysine