Disinhibition reduces extracellular glutamine and elevates extracellular glutamate in rat hippocampus in vivo.
Disinhibition reduces extracellular glutamine and elevates extracellular glutamate in rat hippocampus in vivo.
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DOI：
10.1016/j.eplepsyres.2015.03.009
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发表时间：
2015-08
影响因子：
2.2
通讯作者：
Kanamori K
中科院分区：
文献类型：
--
作者：
Kanamori K
用微透析探针单侧灌流GABA受体拮抗剂氢溴酸(4-[6-imino-3-(4-methoxyphenyl)pyridazin-1-yl]butanoic)或GABA受体拮抗剂对-(3-氨丙基)-对-二乙氧基甲基膦酸(CGP-35348)，可使正常成年大鼠海马区CA1/CA3区去抑制。本实验观察了去抑制对自由活动大鼠双侧脑电记录及其主要兴奋性神经递质细胞外谷氨酸(GLUECF)及其前体谷氨酰胺(GLNECF)浓度的影响。在正常电解质组成的人工脑脊液中单侧灌流10μM加巴嗪34min，不仅在加巴嗪灌流的同侧海马区，而且在对侧脑脊液灌流的对侧海马区，均可诱发癫痫样放电，表现为谷氨酸能群体同步爆发。GLUECF的浓度没有变化，但其前体GLNECF的浓度在癫痫样放电频繁时下降到基线的73±4%(n=5)，不仅在同侧，而且在对侧海马，这种变化可以归因于癫痫样放电本身的反复，当癫痫样放电减少时，GLNECF的浓度恢复到基线的95%。在同侧海马区灌流CGp 35348 30min阻断GABA受体，可引起双侧细胞外记录的Na+峰。这可以合理地归因于躯体和树突动作电位，并表明同步的兴奋性活动。这种去抑制作用在两个海马区引起：(A)GLUECF一过性升高1.6~2.4倍，这与Na+峰簇数有关；(B)GLNECF同时降低到~70%。采用微透析法，分别在加巴津灌流25min或CGP灌流20min，细胞外Gln(GLNECF)为灌流前的60~70%时，对各组大鼠的脑组织CA1/CA3区细胞内Gln进行测定。这些细胞内谷氨酰胺浓度在去抑制的海马区与未处理的对照组之间没有统计学上的显著差异。这一结果有力地表明，观察到的GLNECF下降并不是由于谷氨酰胺合成减少或Gln向ECF的外流速度下降。这加强了这样一种可能性，即GLNECF的减少反映了神经元对GLN摄取的增加，以在不受抑制的海马区兴奋性群体爆发期间维持增加的GLU流量。这一结果与一个新兴的概念是一致的，即神经元摄取GLNECF在红藻氨酸诱导的颞叶癫痫模型中维持癫痫样活动起主要作用。
Disinhibition was induced in the hippocampal CA1/CA3 region of normal adult rats by unilateral perfusion of the GABAAR antagonist, 4-[6-imino-3-(4-methoxyphenyl)pyridazin-1-yl]butanoic acid hydrobromide (gabazine), or a GABABR antagonist, p-(3-aminopropyl)-p-diethoxymethyl-phosphinic acid (CGP 35348), through a microdialysis probe. Effects of disinhibition on EEG recordings and the concentrations of extracellular glutamate (GLUECF), the major excitatory neurotransmitter, and of extracellular glutamine (GLNECF), its precursor, were examined bilaterally in freely-behaving rats. Unilateral perfusion of 10 μM gabazine in artificial CSF of normal electrolyte composition for 34 min induced epileptiform discharges which represent synchronized glutamatergic population bursts, not only in the gabazine-perfused ipsilateral hippocampus, but also in the aCSF-perfused contralateral hippocampus. The concentration of GLUECF remained unchanged, but the concentration of its precursor, GLNECF, decreased to 73 ± 4% (n = 5) of the baseline during frequent epileptiform discharges, not only in the ipsilateral, but also in the contralateral hippocampus, where the change can be attributed to recurrent epileptiform discharges per se, with recovery to 95% of baseline when epileptiform discharges diminished. The blockade of GABABR, by CGP 35348 perfusion in the ipsilateral hippocampus for 30 min, induced bilateral Na+ spikes in extracellular recording. These can reasonably be attributed to somatic and dendritic action potentials and are indicative of synchronized excitatory activity. This disinhibition induced, in both hippocampi, (a) transient 1.6 to 2.4- fold elevation of GLUECF which correlated with the number of Na+ spike cluster events and (b) concomitant reduction of GLNECF to ~70%. Intracellular GLN concentration was measured in the hippocampal CA1/CA3 region sampled by microdialysis in separate groups of rats by snap-freezing the brain after 25 min of gabazine perfusion or 20 min of CGP perfusion when extracellular GLN (GLNECF) was 60-70% of the pre-perfusion level. These intracellular GLN concentrations in the disinhibited hippocampi showed no statistically significant difference from the untreated control. This result strongly suggests that the observed decrease of GLNECF is not due to reduced glutamine synthesis or decrease in the rate of efflux of GLN to ECF. This strengthens the likelihood that reduced GLNECF reflects increased GLN uptake into neurons to sustain enhanced GLU flux during excitatory population bursts in disinhibited hippocampus. The results are consistent with the emerging concept that neuronal uptake of GLNECF plays a major role in sustaining epileptiform activities in the kainate-induced model of temporal-lobe epilepsy.
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影响因子：
5
作者：
LANZA, M;FASSIO, A;RAITERI, M
通讯作者：
RAITERI, M
影响因子：
25
作者：
Lovett-Barron, Matthew;Turi, Gergely F.;Losonczy, Attila
通讯作者：
Losonczy, Attila
影响因子：
2.9
作者：
BUZSAKI, G
通讯作者：
BUZSAKI, G
影响因子：
5
作者：
OLPE, HR;KARLSSON, G;BITTIGER, H
通讯作者：
BITTIGER, H
DOI：
10.1073/pnas.93.18.9921
发表时间：
1996-09-03
影响因子：
11.1
作者：
Buzsaki, G;Penttonen, M;Bragin, A
通讯作者：
Bragin, A