Arias C, Sitges M, Tapia R
J Neurochem. 1984 Jun;42(6):1507-14. doi: 10.1111/j.1471-4159.1984.tb12736.x.
The effect of EGTA on the release of labeled gamma-aminobutyric acid (GABA), glutamate, acetylcholine, and dopamine was studied in superfused synaptosomes from mouse brain. In the absence of both Ca2+ and Mg2+, EGTA and also EDTA at 50 microM or higher concentrations induced a 2.5-5-fold stimulation of [3H]GABA release, similar to that produced by potassium depolarization, whereas only a slight effect, or no effect at all, was observed on the release of the other transmitters studied. The GABA-releasing action of EGTA was practically abolished in the presence of Mg2+. In contrast, the effect of EDTA was also observed when the medium contained Mg2+. Studies on the ionic dependence showed that the stimulation of GABA release by EGTA was abolished in a Na+-free medium. Li+ did not substitute Na+ for the EGTA effect, which was also independent of chloride. This Na+ dependence does not seem to involve voltage-sensitive channels, since tetrodotoxin did not affect the GABA-releasing action of EGTA, whereas in parallel superfusion chambers it blocked over 80% the stimulation of GABA release by veratridine. In contrast, two calcium channel blockers in synaptosomes, La3+ and the cationic dye ruthenium red, greatly inhibited the GABA-releasing effect of EGTA. L-2,4-Diaminobutyric acid, an inhibitor of the Na+-dependent GABA carrier, did not affect the releasing action of EGTA, whereas in a parallel experiment this drug inhibited by more than 90% the exchange of labeled GABA with unlabeled GABA.(ABSTRACT TRUNCATED AT 250 WORDS)
在来自小鼠脑的灌流突触体中研究了乙二醇双乙醚二胺四乙酸（EGTA）对标记的γ-氨基丁酸（GABA）、谷氨酸、乙酰胆碱和多巴胺释放的影响。在不存在Ca2+和Mg2+的情况下，50μM或更高浓度的EGTA以及乙二胺四乙酸（EDTA）诱导[3H]GABA释放增加2.5至5倍，类似于钾去极化所产生的增加，而对所研究的其他递质的释放仅观察到轻微影响或根本没有影响。在存在Mg2+的情况下，EGTA的GABA释放作用实际上被消除。相反，当培养基中含有Mg2+时也观察到EDTA的作用。离子依赖性研究表明，在无钠培养基中EGTA对GABA释放的刺激作用被消除。Li+不能替代Na+发挥EGTA的作用，且该作用也与氯离子无关。这种对Na+的依赖性似乎不涉及电压敏感通道，因为河豚毒素不影响EGTA的GABA释放作用，而在平行灌流室中它能阻断藜芦碱对GABA释放刺激作用的80%以上。相反，突触体中的两种钙通道阻滞剂La3+和阳离子染料钌红极大地抑制了EGTA的GABA释放作用。L-2,4-二氨基丁酸是一种钠依赖性GABA载体的抑制剂，不影响EGTA的释放作用，而在平行实验中该药物抑制标记的GABA与未标记的GABA交换的作用超过90%。（摘要截短于250字）
