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Front. Neuroanat. | doi: 10.3389/fnana.2018.00116

Postnatal development of NPY and Somatostatin-28 peptidergic populations in the human angular bundle.

  • 1Department of Health Sciences, University of Castilla La Mancha, Spain
  • 2Centro Regional de Investigaciones Biomédicas, Universidad de Castilla-La Mancha, Spain
  • 3Degree in Physiotherapy, Public University of Navarra, Spain
  • 4Universität Potsdam, Germany

The angular bundle is a white matter fiber fascicle, which runs longitudinally along the parahippocampal gyrus. It is best known for carrying fibers from the entorhinal cortex to the hippocampus through the perforant and alvear pathways, as well as for carrying hippocampal output to the neocortex, and distributing fibers to polysensory cortex.
The angular bundle is already present prenatally at the beginning of the fetal period. Connections between the entorhinal cortex and the hippocampus are established by the 20th gestational week. In the postnatal period, it shows increasing myelination.
The angular bundle, as well as other white matter portions of gyral surfaces in the brain, presents interstitial neurons, a remnant of subplate neurons. Those interstitial neurons show neurochemical phenotypes both prenatally and postnatally, among which, neuropeptide Y (NPY) and Somatostatin-28 (SOM) peptidergic populations are noticeable, and accompany the fiber connections in the maturation of the hippocampal formation. We sought to investigate the topography of the postnatal distribution and relative density of neurons immunoreactive for NPY or SOM in the angular bundle along the rostrocaudal axis of the hippocampus. The study was carried out in 15 cases, ranging from 35 gestational weeks, up to 14 years old. All cases showed positive neurons showing a polygonal or spindle shaped morphology for both peptides, scattered throughout the angular bundle. The highest number of positive neurons appeared around birth and the ensuing weeks. Up to one and a half years, the density of both peptidergic populations decreased slightly. However, cases older than two years of age showed a substantial decrease in density of immunolabeled neurons, density that did not showed a minor decrease in density of positive neurons in cases older than two years. In addition, a topography from caudal to rostral levels of the angular bundle was detected at all ages.
The functional significance of interstitial cells is unknown, but the existence of SOM and NPY peptidergic neurons, presumably inhibitory, in the white matter of the angular bundle, could contribute to the basic wiring of the hippocampal formation, through which autobiographical and spatial memories can begin to be stored in the infant brain.

Keywords: Human Development, white matter, angular bundle, Neuropeptide Y, Somatostatin-28

Received: 12 Jul 2018; Accepted: 05 Dec 2018.

Edited by:

Kathleen S. Rockland, School of Medicine, Boston University, United States

Reviewed by:

Joachim H. Lübke, Forschungszentrum Jülich, Helmholtz Association of German Research Centers (HZ), Germany
Xavier Leinekugel, Institut National de la Santé et de la Recherche Médicale (INSERM), France  

Copyright: © 2018 Cebada-Sanchez, Marcos-Rabal, Insausti Serrano, Matthews and Insausti. 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. Ricardo Insausti, University of Castilla La Mancha, Department of Health Sciences, Ciudad Real, 02006, Albacete, Spain, Ricardo.Insausti@uclm.es