Riebe Ilse, Gustafsson Bengt, Hanse Eric
Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
Eur J Neurosci. 2009 May;29(9):1870-82. doi: 10.1111/j.1460-9568.2009.06734.x. Epub 2009 Apr 17.
Glutamate transmission to gamma-aminobutyric acid (GABA)ergic interneurons and to principal neurons differs in various important respects. Whether these differences exist from an early developmental stage, or result from differential development from a more common state, is unclear. In the hippocampal CA1 area, glutamate transmission to the developing, but not to the adult, principal neurons is characterized by the presence of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) silent synapses and of AMPA silencing induced by test pulse stimulation (0.03-1 Hz). In the present study, we examined whether this developmental difference in AMPA signaling is also true for glutamate transmission to CA1 stratum radiatum interneurons. We found that AMPA silent synapses onto these interneurons also exist, and that they can be generated by test pulse stimulation. In marked contrast to AMPA silencing in principal neurons, AMPA silencing in interneurons was not developmentally restricted, but was observed to the same extent after the first postnatal month as in the second postnatal week. In addition, we found that glutamate synapses onto these interneurons can also be N-methyl-d-aspartate (NMDA)-silent, that is, only AMPA-signaling. After test pulse stimulation, the AMPA-silent, the NMDA-silent and the AMPA/NMDA-signaling synapses onto the developing interneurons were estimated to be about equally frequent. These results highlight a diversity of glutamate signaling to CA1 stratum radiatum interneurons, and they indicate that the glutamate synapses onto pyramidal neurons and to interneurons can mature differentially.
谷氨酸传递至γ-氨基丁酸（GABA）能中间神经元和投射至主要神经元在多个重要方面存在差异。这些差异是从早期发育阶段就已存在，还是由更普遍状态下的不同发育过程导致，目前尚不清楚。在海马CA1区，谷氨酸传递至发育中的主要神经元（而非成年主要神经元）的特征是存在α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）沉默突触以及由测试脉冲刺激（0.03 - 1赫兹）诱导的AMPA沉默。在本研究中，我们探究了这种AMPA信号传导的发育差异对于谷氨酸传递至CA1放射层中间神经元是否同样成立。我们发现，这些中间神经元上也存在AMPA沉默突触，并且它们可由测试脉冲刺激产生。与主要神经元中的AMPA沉默形成显著对比的是，中间神经元中的AMPA沉默不受发育限制，在出生后第一个月与出生后第二周观察到相同程度的AMPA沉默。此外，我们发现谷氨酸突触至这些中间神经元也可以是N-甲基-D-天冬氨酸（NMDA）沉默的，即仅具有AMPA信号传导。在测试脉冲刺激后，发育中的中间神经元上的AMPA沉默、NMDA沉默以及AMPA/NMDA信号传导突触估计出现频率大致相同。这些结果突出了谷氨酸传递至CA1放射层中间神经元的多样性，并且表明谷氨酸突触至锥体神经元和中间神经元的成熟过程可能存在差异。
