Somatostatin peptides produce multiple effects on Gating properties of native cone photoreceptor cGMP-Gated channels that depend on circadian phase and previous illumination
Somatostatin peptides produce multiple effects on Gating properties of native cone photoreceptor cGMP-Gated channels that depend on circadian phase and previous illumination
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DOI：
10.1523/jneurosci.3541-07.2007
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发表时间：
2007-11-07
影响因子：
5.3
通讯作者：
Dryer, Stuart E.
中科院分区：
文献类型：
--
作者：
Chen, Shih-Kuo;Ko, Gladys Y. -P.;Dryer, Stuart E.
鸟类无长突细胞亚群表达生长抑素-14（SS 14）和生长抑素-28（SS 28），它们为光感受器的光依赖性调节提供了潜在的传出肢。在这里，我们证明SS 14和SS 28通过多种机制调节视锥细胞cGMP门控通道（CNGC）。在先前夹带到亮-暗（LD）循环后在恒定黑暗中培养2天的鸡视锥中或在维持在LD中的细胞中，应用100 nM SS 14或100 nM SS 28 15 min或2 h导致CNGC在夜间，在昼夜节律时间16（CT 16）-CT 20或Zeitgeber时间16（ZT 16）-ZT 20对cGMP的敏感性降低。SS 14在白天（CT 4-CT 8或ZT 4-ZT 8）没有作用。这些效应在用百日咳毒素（PTX）预处理的细胞中持续存在，并且像多巴胺一样，可能会加强由光感受器本身内的振荡器驱动的CNGC的长期昼夜节律波动。相比之下，15分钟暴露于SS 28导致CNGC对cGMP的敏感性在早期（ZT 4-ZT 6）似乎矛盾的增加，但仅在LD中维持的视锥细胞中。SS 28的这种作用迅速脱敏，被PTX预处理阻断，并被环己肽激动剂MK-678选择性模仿。这种短暂反应还需要激活磷脂酶C和蛋白激酶C。对SS 28的瞬态响应可能在光感受器适应环境照明的快速变化中起作用。这些数据还表明，光感受器对至少一些肽类神经递质的反应取决于先前的光暴露史。
A subpopulation of avian amacrine cells expresses somatostatin-14 (SS14) and somatostatin-28 (SS28), which provide a potential efferent limb for light-dependent regulation of photoreceptors. Here, we demonstrate that SS14 and SS28 modulate cone photoreceptor cGMP-gated channels (CNGCs) through multiple mechanisms. In chicken cones cultured in constant darkness for 2 d after previous entrainment to light-dark (LD) cycles or in cells maintained in LD, application of 100 nM SS14 or 100 nM SS28 for either 15 min or 2 h caused a decrease in the sensitivity of CNGCs to cGMP during the night, at circadian time 16 (CT16)-CT20 or zeitgeber time 16 (ZT16)-ZT20. SS14 had no effect during the day (CT4-CT8 or ZT4-ZT8). These effects persist in cells pretreated with pertussis toxin (PTX) and, like dopamine, may work to reinforce long-term circadian fluctuations in CNGCs driven by oscillators within the photoreceptors themselves. In contrast, a 15 min exposure to SS28 caused a seemingly paradoxical increase in the sensitivity of CNGCs to cGMP during the early day (ZT4-ZT6), but only in cones maintained in LD. This effect of SS28 desensitizes rapidly, is blocked by pretreatment with PTX, and is selectively mimicked by the cyclohexapeptide agonist MK-678. This transient response also requires activation of phospholipase C and protein kinase C. The transient response to SS28 may play a role in photoreceptor adaptation to rapid changes in ambient illumination. These data also show that photoreceptor responses to at least some peptide neurotransmitters depend on the previous history of light exposure.