Brain photoreceptor pathways contributing to circadian rhythmicity in crayfish.
Brain photoreceptor pathways contributing to circadian rhythmicity in crayfish.
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DOI：
10.3109/07420520903217960
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发表时间：
2009-08
影响因子：
2.8
通讯作者：
Sandeman DC
中科院分区：
文献类型：
--
作者：
Sullivan JM;Genco MC;Marlow ED;Benton JL;Beltz BS;Sandeman DC
淡水螯虾有三种已知的光感受系统：复眼、视网膜外脑光感受器和尾部光感受器。这里描述的工作的主要目标是探索大脑光感受器对昼夜运动活动的贡献，并定义一些潜在的神经通路。免疫细胞化学研究的大脑光感受器在寄生酸（南半球）螯虾Cherax destructor揭示他们的表达的蓝光敏感色素隐花色素和神经递质组胺。脑光感受器投射到两个小的前脑神经末梢，即脑光感受器神经末梢（brain photoreceptor neuropil，BPN），在那里它们终止于表达神经肽色素分散激素（PDH）的纤维之间，PDH是节肢动物昼夜节律系统中的信号分子。类似的途径也描述在astacid（北方）克氏原螯虾。尽管表现出明显不同的昼夜运动活动节律，去除复眼和尾部光感受器在两个C。destructor和P. clarkii的光感受器（保持脑光感受器完整）不会消除两个物种中正常的光/暗活动周期，也不会阻止它们的活动周期夹带到光/暗周期的相移中。这些结果表明，因此，小龙虾脑光感受器是足够的夹带的局部运动活动节奏的光刺激，并且它们可以在没有复眼和尾部光感受器的情况下起作用。我们还表明，在BPN的PDH表达的强度变化的阶段与运动的活动节奏的小龙虾物种。总之，这些研究结果表明，大脑感光细胞可以作为视网膜外昼夜光感受器，BPN代表了一个夹带途径的一部分，同步运动活动的环境光/暗周期，并牵连神经肽PDH在这些功能。（作者通讯：bbeltz@wellesley.edu）
Freshwater crayfish have three known photoreceptive systems: the compound eyes, extraretinal brain photoreceptors, and caudal photoreceptors. The primary goal of the work described here was to explore the contribution of the brain photoreceptors to circadian locomotory activity and define some of the underlying neural pathways. Immunocytochemical studies of the brain photoreceptors in the parastacid (southern hemisphere) crayfish Cherax destructor reveal their expression of the blue light-sensitive photopigment cryptochrome and the neurotransmitter histamine. The brain photo-receptors project to two small protocerebral neuropils, the brain photoreceptor neuropils (BPNs), where they terminate among fibers expressing the neuropeptide pigment-dispersing hormone (PDH), a signaling molecule in arthropod circadian systems. Comparable pathways are also described in the astacid (northern hemisphere) crayfish Procambarus clarkii. Despite exhibiting markedly different diurnal locomotor activity rhythms, removal of the compound eyes and caudal photoreceptors in both C. destructor and P. clarkii (leaving the brain photoreceptors intact) does not abolish the normal light/dark activity cycle in either species, nor prevent the entrainment of their activity cycles to phase shifts of the light/dark period. These results suggest, therefore, that crayfish brain photoreceptors are sufficient for the entrainment of loco-motor activity rhythms to photic stimuli, and that they can act in the absence of the compound eyes and caudal photoreceptors. We also demonstrate that the intensity of PDH expression in the BPNs varies in phase with the locomotor activity rhythm of both crayfish species. Together, these findings suggest that the brain photoreceptor cells can function as extraretinal circadian photoreceptors and that the BPN represents part of an entrainment pathway synchronizing locomotor activity to environmental light/dark cycles, and implicating the neuropeptide PDH in these functions. (Author correspondence: bbeltz@wellesley.edu)