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Analysis of presynaptic guanylyl cyclase cascade during adrenergic enhancement of transmitter release

肾上腺素能增强递质释放过程中突触前鸟苷酸环化酶级联的分析

基本信息

批准号：
09480236
负责人：
YAWO Hiromu
金额：
$ 8.13万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

We have previously reported that norepinephrine (NE) induces a sustained potentiation of transmitter release in the chick ciliary ganglion through a mechanism pharmacologically distinct form any known adrenergic receptors. Here we report that the adrenergic potentiation of transmitter release was enhanced by a phosphodiesterase (PDE) inhibitor, 3-isobutyl-1-methylxanthine (IBMX) and by zaprinast, an inhibitor of cGMP-selective phosphodiesterase. Exogenous application of the membrane-permeable cGMP, 8Br-cGMP, potentiated the quantal transmitter release and, after potentiation, the addition of NE was no longer effective. On the other hand, 8Br-cAMP neither potentiated the transmitter release nor occluded the NE-induced potentiation. The NE-induced potentiation was blocked by neither NO synthase inhibitor nor NO scavenger. The quantal transmitter release was not potentiated by NO donors, e.g. sodium nitroprusside (SNP). The NE-induced potentiation and its enhancement by IBMX was antagonized by two inhibitors of protein kinase G (PKG), Rp-8pCPT-cGMPS and KT5823. As with NE-induced potentiation, the effects of 8Br-cGMP on both the resting [CaィイD12+ィエD1]ィイD2iィエD2 and the action potential-dependent increment of [CaィイD12+ィエD1]ィイD2iィエD2 (ΔCa) in the presynaptic terminal were negligible. The reduction of the paired-pulse ratio of EPSC is consistent with the notion that the NE/cGMP-dependent poteitiation of transmitter release was due mainly to an increase of the exocytotic fusion probability. These results indicate that NE binds to a novel adrenergic receptor that activate guanylyl cyclase and that accumulation of cGMP activates PKG, which may phosphorylate a target protein involved in the exocytosis of synaptic vesicles.

我们以前曾报道去甲肾上腺素（NE）通过一种不同于任何已知肾上腺素能受体的机制诱导鸡睫状神经节递质释放的持续增强。在这里，我们报告说，肾上腺素能增强发射机释放增强磷酸二酯酶（PDE）抑制剂，3-异丁基-1-甲基黄嘌呤（IBMX）和扎普司特，cGMP选择性磷酸二酯酶抑制剂。外源性应用的膜渗透性cGMP，8Br-cGMP，增强量子递质的释放，增强后，NE的加入不再有效。另一方面，8Br-cAMP既不增强递质释放，也不阻断NE诱导的增强作用。NO合成酶抑制剂和NO清除剂均不能阻断NE的增强作用。量子递质的释放没有增强NO供体，如硝普钠（SNP）。蛋白激酶G（PKG）抑制剂Rp-8 pCPT-cGMPS和KT 5823可拮抗NE诱导的增强作用和IBMX的增强作用。与NE诱导的增强作用一样，8 Br-cGMP对突触前末梢静息[Ca ~（2+）D_12 + Ca ~（2+）D_1] Ca ~（2+）D_2和动作电位依赖性增加[Ca ~（2+）D_12 + Ca ~（2+）D_1] Ca ~（2+）D_2（ΔCa）的影响可忽略不计。EPSC双脉冲比的降低与NE/cGMP依赖性递质释放的增加主要是由于胞吐融合概率的增加的观点一致。这些结果表明，NE结合到一种新的肾上腺素能受体，激活鸟苷酸环化酶和cGMP的积累激活PKG，这可能磷酸化参与突触囊泡胞吐的靶蛋白。