Neurotransmitter release at ribbon synapses in the retina
Neurotransmitter release at ribbon synapses in the retina
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DOI：
10.1046/j.1440-1711.2000.00923.x
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发表时间：
2000-08-01
影响因子：
4
通讯作者：
Morgans, CW
中科院分区：
文献类型：
--
作者：
Morgans, CW
视网膜中光感受器和双极细胞的突触在超微结构上很容易被识别，突触带是在活动区垂直于质膜的电子致密条，延伸到细胞质中约0.5微米。神经递质谷氨酸从这些“带状突触”持续(强直地)释放出来，释放的速度随着膜电位的逐渐变化而变化。这与传统突触由动作电位驱动的释放形成了鲜明对比。与其他突触相似，神经递质是通过突触小泡的钙依赖性胞吐作用在带状突触释放的。调节递质释放的分子机制的大部分成分在带状突触和常规突触之间是保守的，但已发现一些差异可能是紧张性递质释放的重要决定因素。例如，双极细胞和光感受器的突触前钙通道与大脑其他地方的不同。在涉及突触小泡重新聚集到活动区和突触小泡融合的蛋白质方面也发现了差异。这些差异和其他差异在它们对视网膜光感受器和双极细胞神经递质释放的影响方面进行了讨论。
The synapses of photoreceptors and bipolar cells in the retina are easily identified ultrastructurally by the presence of synaptic ribbons, electron-dense bars perpendicular to the plasma membrane at the active zones, extending about 0.5 mu m into the cytoplasm. The neurotransmitter, glutamate, is released continuously (tonically) from these 'ribbon synapses' and the rate of release is modulated in response to graded changes in the membrane potential. This contrasts with action potential-driven bursts of release at conventional synapses. Similar to other synapses, neurotransmitter is released at ribbon synapses by the calcium-dependent exocytosis of synaptic vesicles. Most components of the molecular machinery governing transmitter release are conserved between ribbon and conventional synapses, but a few differences have been identified that may be important determinants of tonic transmitter release. For example, the presynaptic calcium channels of bipolar cells and photoreceptors are different from those elsewhere in the brain. Differences have also been found in the proteins involved in synaptic vesicle recruitment to the active zone and in synaptic vesicle fusion. These differences and others are discussed in terms of their implications for neurotransmitter release from photoreceptors and bipolar cells in the retina.