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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Syst. Neurosci. | doi: 10.3389/fnsys.2019.00054

Entorhinal layer II calbindin-expressing neurons originate widespread telencephalic and intrinsic projections

 Shinya Ohara1, 2,  Michele Gianatti2, 3, Kazuki Itou1,  Christin H. Berndtsson2,  Thanh P. Doan2,  Takuma Kitanishi4, Kenji Mizuseki4, Toshio Iijima1, Ken-Ichiro Tsutsui1 and  Menno P. Witter2*
  • 1Laboratory of Systems Neuroscience, Graduate School of Life Sciences, Tohoku University, Japan
  • 2Kavli Institute for Systems Neuroscience, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Norway
  • 3Faculty of Medicine, University of Oslo, Norway
  • 4Graduate School of Medicine, Osaka City University, Japan

In the present study we provide the first systematic and quantitative hodological study of the calbindin-expressing (CB+) principal neurons in layer II of the entorhinal cortex and compared the respective projections of the lateral and medial subdivisions of the entorhinal cortex. Using elaborate quantitative retrograde tracing, complemented by anterograde tracing, we report that the layer II CB+ population comprises neurons with diverse, mainly excitatory projections. At least half of them originate local intrinsic and commissural projections which distribute mainly to layer I and II. We further show that long-range CB+ projections from the two entorhinal subdivisions differ substantially in that MEC projections mainly target field CA1 of the hippocampus, whereas LEC CB+ projections distribute much more widely to a substantial number of known forebrain targets. This connectional difference between the CB+ populations in LEC and MEC is reminiscent of the overall projection pattern of the two entorhinal subdivisions.

Keywords: Medial entorhinal cortex (MEC), Lateral entorhinal cortex (LEC), parahippocampus, connectivity, rodent, long-range intrinsic projections, commissural projections

Received: 23 May 2019; Accepted: 30 Sep 2019.

Copyright: © 2019 Ohara, Gianatti, Itou, Berndtsson, Doan, Kitanishi, Mizuseki, Iijima, Tsutsui and Witter. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Menno P. Witter, Kavli Institute for Systems Neuroscience, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway,