Wyatt S, Davies A M
School of Biological and Medical Sciences, University of St. Andrews, Fife, Scotland.
Development. 1993 Nov;119(3):635-48. doi: 10.1242/dev.119.3.635.
We have used a quantitative reverse transcription/polymerase chain reaction amplification technique to study the regulation of p75 mRNA and trkA mRNA expression in developing NGF-dependent trigeminal neurons. Before becoming NGF dependent, these neurons express low levels of p75 and trkA mRNAs in vivo. At this stage in vitro, the level of p75 mRNA is maintained and up-regulated by BDNF, whereas the level of trkA mRNA is sustained independently of neurotrophins and is down-regulated by BDNF. With the acquisition of NGF dependence, p75 and trkA mRNA levels increase markedly in vivo. At this stage in vitro, the level of p75 mRNA is up-regulated by NGF, but this response is lost at later stages. The level of trkA mRNA is sustained in neurons grown with NGF but is not up-regulated by concentrations of NGF above those required to support survival. At no stage during the early development of trigeminal neurons do depolarising levels of potassium ions affect the expression of either p75 mRNA or trkA mRNA. These findings suggest that the expression of p75 and trkA mRNAs are differentially regulated by BDNF and NGF at successive early stages of neuronal development.
我们运用定量逆转录/聚合酶链反应扩增技术，研究在发育中的NGF依赖性三叉神经元中p75 mRNA和trkA mRNA表达的调控。在变得依赖NGF之前，这些神经元在体内表达低水平的p75和trkA mRNA。在此阶段的体外培养中，p75 mRNA的水平由BDNF维持并上调，而trkA mRNA的水平独立于神经营养因子得以维持，并被BDNF下调。随着对NGF依赖性的获得，p75和trkA mRNA水平在体内显著增加。在此阶段的体外培养中，p75 mRNA的水平由NGF上调，但此反应在后期阶段消失。trkA mRNA的水平在与NGF一起生长的神经元中得以维持，但不会被高于支持存活所需浓度的NGF上调。在三叉神经元早期发育的任何阶段，去极化水平的钾离子均不影响p75 mRNA或trkA mRNA的表达。这些发现表明，在神经元发育的连续早期阶段，p75和trkA mRNA的表达受到BDNF和NGF的不同调控。
