Minc-Golomb D, Eimerl S, Levy Y, Schramm M
Department of Biological Chemistry, Hebrew University of Jerusalem, Israel.
Brain Res. 1988 Aug 9;457(2):205-11. doi: 10.1016/0006-8993(88)90687-7.
Extended incubation of hippocampus slices in the presence of fatty acid-free bovine serum albumin (FAF-BSA) strongly enhanced the release of D-[3H]aspartate and [14C]GABA induced by veratridine. Saturation of the FAF-BSA with oleic acid abolished the enhancing effect. Spontaneous release and K+-induced release were not significantly changed by the addition of FAF-BSA. Amino-oxyacetic acid in the medium enhanced the veratridine-induced release of D-[3H] aspartate. The spontaneous release of [14C]GABA was greatly increased by Ca2+ withdrawal. With the further addition of EGTA the spontaneous release in the absence of Ca2+ increased more than 8-fold over the measured in the presence of 1.5 mM Ca2+. The enhanced release caused by Ca2+ withdrawal was totally blocked by tetrodotoxin. The toxin was effective even when added after the spontaneous release in the absence of Ca2+ was already proceeding at a high rate. The veratridine-induced release of [14C]GABA was also considerably augmented by Ca2+ withdrawal. D-[3H]aspartate release, studied simultaneously with [14C]GABA by double labeling, did not show enhanced spontaneous release upon Ca2+ withdrawal. The findings provide evidence that the enhanced [14C]GABA release caused by Ca2+ withdrawal is mediated by voltage-dependent Na+ channels.
在无脂肪酸牛血清白蛋白（FAF - BSA）存在的情况下，海马切片的长时间孵育强烈增强了藜芦碱诱导的D - [3H]天冬氨酸和[14C]GABA的释放。用油酸使FAF - BSA饱和消除了增强作用。添加FAF - BSA对自发释放和K⁺诱导的释放没有显著影响。培养基中的氨基氧乙酸增强了藜芦碱诱导的D - [3H]天冬氨酸的释放。Ca²⁺去除极大地增加了[14C]GABA的自发释放。进一步添加EGTA后，无Ca²⁺时的自发释放比在1.5 mM Ca²⁺存在下测量的值增加了8倍以上。Ca²⁺去除引起的释放增强被河豚毒素完全阻断。即使在无Ca²⁺时自发释放已经以高速率进行后添加该毒素，它仍然有效。藜芦碱诱导的[14C]GABA释放也因Ca²⁺去除而显著增加。通过双重标记与[14C]GABA同时研究的D - [3H]天冬氨酸释放，在Ca²⁺去除时未显示出自发释放增强。这些发现提供了证据，表明Ca²⁺去除引起的[14C]GABA释放增强是由电压依赖性Na⁺通道介导的。
