Inhibition of glutamate/glutamine cycle in vivo results in decreased benzodiazepine binding and differentially regulated GABAergic subunit expression in the rat brain
Inhibition of glutamate/glutamine cycle in vivo results in decreased benzodiazepine binding and differentially regulated GABAergic subunit expression in the rat brain
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DOI：
10.1111/j.1528-1167.2010.02562.x
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发表时间：
2010-08-01
期刊：
影响因子：
5.6
通讯作者：
Zilles, Karl
中科院分区：
文献类型：
--
作者：
Cremer, Christian M.;Bidmon, Hans-Juergen;Zilles, Karl
目的：星形胶质细胞谷氨酰胺合成酶（GS）是谷氨酸/谷氨酰胺循环（GGC）中谷氨酸和γ-氨基丁酸（GABA）代谢的关键调节因子。GS的抑制导致神经递质释放和再循环的变化。然而，很少有人知道GGC对神经递质受体表达的影响。在戊四唑癫痫模型中，GS被硝化和部分抑制，我们证明了在同一模型中神经递质受体表达的改变。因此，我们假设类似的神经递质受体表达的变化时，GS是inhibitedinvivo.Methods：大鼠进行了治疗与单剂量（100 mg/kg体重）的L-蛋氨酸亚砜亚胺（MSO），GS的不可逆抑制剂。我们使用3 H受体放射自显影术测量了多巴胺能[α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）、红藻氨酸盐、N-甲基-d-天冬氨酸（NMDA）]、GABA能（GABA（A）、GABA（B）和GABA（A）相关苯二氮卓类（BZ）结合位点]、多巴胺D-1和腺苷A（1）受体亚型。此外，我们进行了饱和度分析的BZ结合位点的大脑膜匀浆和GABA（A）α（1）和γ（2）亚基（主要介导BZ结合）的表达通过western blot analysis.Results：我们证明了BZ结合在躯体感觉，梨状，内嗅皮质和杏仁核，24和72小时后MSO治疗的显着减少。饱和度分析显示，MSO处理后72 h，脑膜匀浆上的BZ结合（B-max）降低，结合位点亲和力（K-D）无变化。此外，我们发现不同的变化，α（1），γ（2），和磷酸化的γ（2）亚基后MSO treatment.Conclusion：在我们的研究结果的基础上，我们得出结论，谷氨酸/谷氨酰胺循环直接影响GABA能神经传递通过调节GABA（A）亚基的组成，从而影响其调制内源性苯二氮卓类。
P>Purpose:The astrocytic enzyme glutamine synthetase (GS) is a key regulator of glutamate and gamma-aminobutyric acid (GABA) metabolism in the glutamate/glutamine cycle (GGC). Inhibition of GS results in changes of neurotransmitter release and recycling. However, little is known about the influence of GGC on neurotransmitter receptor expression. In the pentylenetetrazole model of epilepsy, GS becomes nitrated and partially inhibited, and we demonstrated alterations of neurotransmitter receptor expression in the same model. Therefore, we hypothesized similar changes of neurotransmitter receptor expression when GS is inhibited in vivo.Methods:Rats were treated with a single dose (100 mg/kg bodyweight) of l-methionine sulfoximine (MSO), an irreversible inhibitor of GS. We used 3H-receptor autoradiography to measure glutamatergic [alpha-amino-3-hydroxy-5-methyl-4-isoxazol-propionic acid (AMPA), kainate, N-methyl-d-aspartate (NMDA)], GABAergic (GABA(A), GABA(B) and GABA(A)-associated benzodiazepine (BZ) binding sites], dopamine D-1, and adenosine A(1) receptor subtypes. In addition, we performed saturation analysis of BZ binding sites on cerebral membrane homogenates and investigated the expression of GABA(A) alpha(1) and gamma(2) subunits (which primarily mediate BZ binding) by western blot analysis.Results:We demonstrated a significant reduction of BZ binding in the somatosensory, piriform, and entorhinal cortices and in the amygdala, 24 and 72 h after MSO treatment. Saturation analysis revealed decreased BZ binding (B-max) on cerebral membrane homogenates 72 h after MSO treatment, without changes in binding site affinity (K-D). Furthermore, we found differential changes of alpha(1), gamma(2), and phosphorylated gamma(2) subunits following MSO treatment.Conclusion:On the basis of our findings, we conclude that the glutamate/glutamine cycle directly influences GABAergic neurotransmission by regulating GABA(A) subunit composition, thereby affecting its modulation by endogenous benzodiazepines.