Tokuyama W, Hashimoto T, Li Y X, Okuno H, Miyashita Y
Department of Physiology, University of Tokyo School of Medicine, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan.
Brain Res Mol Brain Res. 1998 Nov 20;62(2):206-15. doi: 10.1016/s0169-328x(98)00261-7.
Brain-derived neurotrophic factor (BDNF) and its receptor, TrkB, regulate synaptic functions in the hippocampus of the adult rodent. In previous studies, in situ hybridization methods have been used to evaluate regional differences in BDNF and trkB mRNA expression levels in hippocampal subregions. However, these studies have failed to reach consensus regarding the regional differences in the mRNA expression levels. In the present study, we quantitated mRNA expression levels using two different methods, ribonuclease protection assays and a quantitative reverse-transcription polymerase chain reaction technique, in four hippocampal subregions: the entorhinal cortex, dentate gyrus (DG), CA3 and CA1. These two methods yielded the same results. We found that BDNF and trkB mRNA expression levels did not covary in the four subregions. BDNF and full length trkB (trkB FL) mRNA in the entorhinal cortex and the DG show contrasting expression patterns. The expression level of BDNF mRNA was highest in the DG among the hippocampal subregions and low in the entorhinal cortex and the CA1, whereas the trkB FL mRNA expression level was highest in the entorhinal cortex, low in the DG and lowest in the CA3. These results suggest regional differences in BDNF/TrkB signaling for maintenance and modifiability of neuronal connections in the hippocampal formation.
脑源性神经营养因子（BDNF）及其受体酪氨酸激酶B（TrkB）可调节成年啮齿动物海马体中的突触功能。在以往的研究中，原位杂交方法已被用于评估海马体各亚区中BDNF和trkB mRNA表达水平的区域差异。然而，这些研究在mRNA表达水平的区域差异方面未能达成共识。在本研究中，我们使用两种不同的方法，即核糖核酸酶保护测定法和定量逆转录聚合酶链反应技术，对海马体的四个亚区：内嗅皮质、齿状回（DG）、CA3和CA1中的mRNA表达水平进行了定量。这两种方法得出了相同的结果。我们发现，BDNF和trkB mRNA表达水平在这四个亚区中并不协同变化。内嗅皮质和DG中的BDNF和全长trkB（trkB FL）mRNA呈现出相反的表达模式。在海马体各亚区中，BDNF mRNA的表达水平在DG中最高，在内嗅皮质和CA1中较低，而trkB FL mRNA的表达水平在内嗅皮质中最高，在DG中较低，在CA3中最低。这些结果表明，在海马结构中，BDNF/TrkB信号在维持和改变神经元连接方面存在区域差异。
