The strength and sign of synapses involving ionotropic GABA and glycine receptors are dependent upon the Cl- gradient. We have shown that nitric oxide (NO) elicits the release of Cl- from internal acidic stores in retinal amacrine cells (ACs); temporarily altering the Cl- gradient and the strength or even sign of incoming GABAergic or glycinergic synapses. The underlying mechanism for this effect of NO requires the cystic fibrosis transmembrane regulator (CFTR) but the link between NO and CFTR activation has not been determined. Here, we test the hypothesis that NO-dependent Ca2+ elevations activate the Ca2+-dependent adenylate cyclase 1 (AdC1) leading to activation of protein kinase A (PKA) whose activity is known to open the CFTR channel. Using the reversal potential of GABA-gated currents to monitor cytosolic Cl-, we established the requirement for Ca2+ elevations. Inhibitors of AdC1 suppressed the NO-dependent increases in cytosolic Cl- whereas inhibitors of other AdC subtypes were ineffective suggesting that AdC1 is involved. Inhibition of PKA also suppressed the action of NO. To address the sufficiency of this pathway in linking NO to elevations in cytosolic Cl-, GABA-gated currents were measured under internal and external zero Cl- conditions to isolate the internal Cl- store. Activators of the cAMP pathway were less effective than NO in producing GABA-gated currents. However, coupling the cAMP pathway activators with the release of Ca2+ from stores produced GABA-gated currents indistinguishable from those stimulated with NO. Together, these results demonstrate that cytosolic Ca2+ links NO to the activation of CFTR and the elevation of cytosolic Cl-.

中文翻译：

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腺苷酸环化酶 1 将钙信号与鸡无长突细胞中依赖于 CFTR 的胞质氯化物升高联系起来。

涉及离子型 GABA 和甘氨酸受体的突触的强度和标志取决于 Cl-梯度。我们已经证明，一氧化氮 (NO) 会引起视网膜无长突细胞 (AC) 内部酸性储存中的 Cl- 释放；暂时改变 Cl-梯度和传入 GABA 能或甘氨酸能突触的强度甚至标志。NO 的这种作用的潜在机制需要囊性纤维化跨膜调节剂 (CFTR)，但尚未确定 NO 和 CFTR 激活之间的联系。在这里，我们测试了以下假设：NO 依赖性 Ca2+ 升高激活 Ca2+ 依赖性腺苷酸环化酶 1 (AdC1)，导致蛋白激酶 A (PKA) 激活，其活性已知可打开 CFTR 通道。使用 GABA 门控电流的逆转电位来监测细胞溶质 Cl-，我们建立了对 Ca2+ 升高的要求。AdC1 的抑制剂抑制了细胞溶质 Cl- 的 NO 依赖性增加，而其他 AdC 亚型的抑制剂无效，表明 AdC1 参与其中。PKA 的抑制也抑制了 NO 的作用。为了解决该通路在将 NO 与细胞溶质 Cl- 升高联系起来的充分性，在内部和外部零 Cl- 条件下测量 GABA 门控电流以隔离内部 Cl- 存储。cAMP 通路的激活剂在产生 GABA 门控电流方面不如 NO 有效。然而，将 cAMP 通路激活剂与从储存中释放的 Ca2+ 结合产生的 GABA 门控电流与用 NO 刺激的电流无法区分。总之，这些结果表明细胞溶质 Ca2+ 将 NO 与 CFTR 的激活和细胞溶质 Cl- 的升高联系起来。