Central regulation of photosensitive membrane turnover in the lateral eye of Limulus. I. Octopamine primes the retina for daily transient rhabdom shedding.
Central regulation of photosensitive membrane turnover in the lateral eye of Limulus. I. Octopamine primes the retina for daily transient rhabdom shedding.
复制标题
鲎外侧眼光敏膜周转的中枢调节。
DOI：
10.1017/s0952523802192066
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发表时间：
2002
影响因子：
1.9
通讯作者：
Jinks,RobertN
中科院分区：
文献类型：
--
作者：
Khadilkar,RashmiV;Mytinger,JohnR;Thomason,LauraE;Runyon,ScottL;Washicosky,KevinJ;Jinks,RobertN
凝胶侧眼每天脱落和更新一部分感光膜(条纹)。在许多物种中，脱落受到昼夜节律和光之间复杂的相互作用的调节。关于生物钟和光感受器如何沟通来调节脱落，我们知之甚少。示踪光感受器不包含内源性的昼夜节律振荡器，但依赖于从中央时钟传出的昼夜节律。为了研究可能的传出神经递质章鱼胺是否传递昼夜节律，从而为眼球短暂性横纹脱落做好准备，我们切断了外侧视神经(包含视网膜传出纤维)，使光感受器与时钟分离。过夜(6h)视网膜内注射40μ甲氧基异丁基异亮氨酸，可恢复有神经切断的侧眼的一过性脱落，恢复到与完整内对照眼相当的水平。为了确定眼压是否在传递昼夜节律方面单独起作用，从而为眼球的一过性脱落做好准备，我们用完整的神经为眼球做好准备，以便在主观的一天中用外源性的眼压进行一过性的眼球流出。在自然界中，在通宵传出启动后，侧眼每天只在黎明时脱掉一次纹状体。在主观白天将动物的眼睛置于黑暗中，此时视网膜传出是静止的，并注射40μM OA 6h，以响应第二次引入光。未经治疗的同一组动物的对照眼则没有。相似处理的侧眼在体外也观察到了同样的结果。章鱼胺是唯一的传出神经递质/信使，需要使侧眼有能力进行短暂的脱落。酚妥拉明是一种OA受体拮抗剂，它减少了为瞬间脱落而准备的光感受器的数量，并减少了这些光感受器中的纹状体数量，表明OA是通过特定的OA受体发挥作用的。
Limulus lateral eyes shed and renew a portion of their photosensitive membrane (rhabdom) daily. Shedding, in many species including Limulus, is regulated by complex interactions between circadian rhythms and light. Little is known about how circadian clocks and photoreceptors communicate to regulate shedding. Limulus photoreceptors do not contain an endogenous circadian oscillator, but rely upon efferent outflow from a central clock for circadian timing. To investigate whether the putative efferent neurotransmitter octopamine (OA) communicates circadian rhythms that prime the lateral eye for transient rhabdom shedding, we decoupled photoreceptors from the clock by transecting the lateral optic nerve (contains the retinal efferent fibers). Overnight (6 h) intraretinal injections of 40 μM OA restored transient shedding to lateral eyes with transected nerves to levels comparable to those of intact internal control eyes. To determine whether OA acts alone in communicating circadian rhythms that prime the lateral eye for transient shedding, we “primed” eyes with intact nerves for transient shedding with exogenous OA during subjective day. In nature, lateral eyes shed their rhabdoms only once a day at dawn following overnight efferent priming. Eyes in animals placed in darkness during subjective day, when the retinal efferents are quiescent, and injected for 6 h with 40 μM OA shed their rhabdoms in response to a second introduction to light. Untreated control eyes of the same animals did not. The same results were observed in vitro in lateral eyes treated similarly. Octopamine is the only efferent neurotransmitter/messenger required to make lateral eyes competent for transient shedding. Phentolamine, an OA receptor antagonist, reduced the number of photoreceptors primed for transient shedding and the amount of rhabdom shed in those photoreceptors suggesting that OA acts via a specific OA receptor.