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 pop...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.展开更多
文摘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.
