Review
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Neurol. Dec 28, 2015; 5(4): 113-131
Published online Dec 28, 2015. doi: 10.5316/wjn.v5.i4.113
Time windows for postnatal changes in morphology and membrane excitability of genioglossal and oculomotor motoneurons
Livia Carrascal, JoséLuis Nieto-González, Ricardo Pardillo-Díaz, Rosario Pásaro, Germán Barrionuevo, Blas Torres, William E Cameron, Pedro Núñez-Abades
Livia Carrascal, JoséLuis Nieto-González, Ricardo Pardillo-Díaz, Rosario Pásaro, Blas Torres, Pedro Núñez-Abades, Department of Physiology, University of Seville, 41012 Seville, Spain
Germán Barrionuevo, Department of Neurocience, University of Pittsburgh, Pittsburgh, PA 15260, United States
William E Cameron, Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, OR 97239, United States
Pedro Núñez-Abades, Departamento de Fisiología, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
Author contributions: All authors contributed to this manuscript.
Conflict-of-interest statement: Authors declare no conflict of interests for this article.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Pedro Núñez-Abades, PhD, Departamento de Fisiología, Facultad de Farmacia, Universidad de Sevilla, C/Profesor García González nº2, 41012 Sevilla, Spain. pnunez@us.es
Telephone: +34-954-556130
Received: August 20, 2015
Peer-review started: August 22, 2015
First decision: September 30, 2015
Revised: November 22, 2015
Accepted: December 7, 2015
Article in press: December 11, 2015
Published online: December 28, 2015
Abstract

Time windows for postnatal changes in morphology and membrane excitability of genioglossal (GG) and oculomotor (OCM) motoneurons (MNs) are yet to be fully described. Analysis of data on brain slices in vitro of the 2 populations of MNs point to a well-defined developmental program that progresses with common age-related changes characterized by: (1) increase of dendritic surface along with length and reshaping of dendritic tree complexity; (2) disappearance of gap junctions early in development; (3) decrease of membrane passive properties, such as input resistance and time constant, together with an increase in the number of cells displaying sag, and modifications in rheobase; (4) action potential shortening and afterhyperpolarization; and (5) an increase in gain and maximum firing frequency. These modifications take place at different time windows for each motoneuronal population. In GG MNs, active membrane properties change mainly during the first postnatal week, passive membrane properties in the second week, and dendritic increasing length and size in the third week of development. In OCM MNs, changes in passive membrane properties and growth of dendritic size take place during the first postnatal week, while active membrane properties and rheobase change during the second and third weeks of development. The sequential order of changes is inverted between active and passive membrane properties, and growth in size does not temporally coincide for both motoneuron populations. These findings are discussed on the basis of environmental cues related to maturation of the respiratory and OCM systems.

Keywords: Development, Motoneurons, Respiratory system, Oculomotor system, Neuronal plasticity

Core tip: For more than 2 decades, numerous studies have tried to describe time windows of changes of membrane properties of motoneurons. This review aims to show what mechanisms are implied in those changes as well as how they are triggered. Our findings are focused on genioglossal and oculomotor motoneurons from birth to adult age. The perspective adopted is the description of how those changes correlate with both intrinsic and extrinsic factors. Data in this review is relevant to understand pathologies related to development.