Derouiche A, Heimrich B, Frotscher M
Institute of Anatomy, University of Frankfurt am Main, Germany.
Eur J Neurosci. 1993 Feb 1;5(2):122-7. doi: 10.1111/j.1460-9568.1993.tb00477.x.
Glutamine synthetase (GS) supposedly inactivates the excitatory neurotransmitter glutamate. By using immunocytochemistry for GS, we recently demonstrated a layer-specific, perisynaptic distribution of GS-immunoreactive astrocytes and their processes in perfusion-fixed rat hippocampi. Highest levels of immunoreactivity were found in well defined termination zones of glutamatergic hippocampal afferents. In the present study we analysed the developmental aspect of this neuron-glia interaction by using hippocampal slice cultures lacking all extrinsic afferents. Under these conditions, no layer-specific distribution of astrocytic GS immunoreactivity could be demonstrated. This suggests that the laminated distribution of GS immunoreactivity is formed in parallel with the segregated termination of hippocampal afferents. Thus, there is no predetermined pattern of GS-containing astrocytes playing a role in the segregation of extrinsic fibres. The ultrastructural localization of GS immunoreactivity in fine astrocytic processes around asymmetric, probably glutamatergic excitatory spine synapses confirms earlier in situ findings, which suggests that this arrangement is a global phenomenon of glutamatergic systems.
谷氨酰胺合成酶（GS）据推测可使兴奋性神经递质谷氨酸失活。通过使用针对GS的免疫细胞化学方法，我们最近在灌注固定的大鼠海马体中证实了GS免疫反应性星形胶质细胞及其突起具有层特异性的突触周围分布。在谷氨酸能海马传入纤维明确的终末区域发现了最高水平的免疫反应性。在本研究中，我们通过使用缺乏所有外在传入纤维的海马切片培养物来分析这种神经元-胶质细胞相互作用的发育情况。在这些条件下，无法证明星形胶质细胞GS免疫反应性的层特异性分布。这表明GS免疫反应性的分层分布是与海马传入纤维的分离终末平行形成的。因此，不存在预先确定的含GS星形胶质细胞模式在外部纤维的分离中起作用。GS免疫反应性在不对称的、可能是谷氨酸能兴奋性棘突触周围的细星形胶质细胞突起中的超微结构定位证实了早期的原位研究结果，这表明这种排列是谷氨酸能系统的一种普遍现象。
