Skaper S D, Varon S
Dev Biol. 1983 Aug;98(2):257-64. doi: 10.1016/0012-1606(83)90356-1.
Using intact dorsal root ganglia (DRG) from embryonic (E) chick and measuring 22Na+ accumulation, the authors have recently shown that (i) ionic control by the ganglia has a complete requirement for exogenous NGF between E6 and E10, and (ii) control of ion pump mechanisms independent of exogenous NGF is progressively acquired by these ganglia from E10 to E16. Similar experiments have now been carried out using enriched suspensions of ganglionic neurons to test whether the acquisition of endogenous control by older ganglia was (1) due to the close association between neurons and nonneurons, and (2) correlated with a decreasing need by these neurons for exogenous NGF for survival in culture. In this enriched neuronal population, Na+ accumulation in the absence of NGF increases from E7 to E10, paralleling the increase in Na+ accessible space under ouabain, but then decreases conspicuously between E10 and E16, despite little change in the ouabain-sensitive Na+ space. NGF prevents Na+ accumulation during the early period, and becomes increasingly irrelevant for this behavior in later (after E10) development. K+ movements (traced with 86Rb+) behaved similarly. Active K+ influx (Na+, K+-pump mediated) also increases severalfold between E7 and E10. This K+ influx is sensitive to NGF at E7 and E10 but not at E14, paralleling the observed Na+ and K+ behaviors. These data suggest that the control of Na+, K+-pump performances acquired by these neurons between E10 and E16 represents the development of a neuronal self-sufficiency. This increase in ionic control is not due to an increase in pump molecules or pumping efficiency. No increases in the binding of [3H]ouabain or active K+ influx occur between E10 and E16, when ionic control is developing. The ionic dependence on NGF by the DRG neurons changes with their developmental age along the same temporal pattern displayed by their survival response to NGF in culture.
作者利用来自胚胎期（E）小鸡的完整背根神经节（DRG）并测量22Na+积累，最近发现：（i）在E6至E10期间，神经节的离子调控对外源性神经生长因子（NGF）有完全需求；（ii）从E10至E16，这些神经节逐渐获得独立于外源性NGF的离子泵机制调控。现在已使用富集的神经节神经元悬液开展了类似实验，以测试较成熟神经节内源性调控的获得是否：（1）由于神经元与非神经元之间的紧密联系；（2）与这些神经元在培养中对外源性NGF生存需求的降低相关。在这个富集的神经元群体中，无NGF时的Na+积累从E7增加至E10，与哇巴因作用下可利用Na+空间的增加平行，但在E10至E16期间显著下降，尽管哇巴因敏感的Na+空间变化不大。NGF在早期可防止Na+积累，而在后期（E10之后）发育中对这种行为的影响越来越小。钾离子（K+）转运（用86Rb+追踪）表现类似。主动钾离子内流（由钠钾泵介导）在E7至E10之间也增加了几倍。这种钾离子内流在E7和E10时对NGF敏感，但在E14时不敏感，与观察到的钠离子和钾离子行为平行。这些数据表明，这些神经元在E10至E16期间获得的钠钾泵性能调控代表了神经元自给自足的发展。离子调控的这种增加并非由于泵分子数量增加或泵浦效率提高。在离子调控发展的E10至E16期间，[3H]哇巴因结合或主动钾离子内流均未增加。DRG神经元对NGF的离子依赖性随其发育年龄变化，与它们在培养中对NGF的存活反应呈现相同的时间模式。
