A study on identification of pre-and postsynaptic neural elements of the circadian pacemaker neurons in insects.

为了揭示节律性运动活动背后的昼夜节律起搏器网络的连接，我们研究了昼夜节律起搏器神经元的突触前和突触后神经元件，以果蝇（Drosophila melanogaster）和原生鼠（protophoria terraenovae）为模式生物。P. terraenovae具有PDF（色素分散因子）免疫阳性神经元（这里称为Pt-PDF/LNs），与果蝇的PDF免疫阳性s-LNvs（小腹侧神经元）相对应，后者起昼夜节律起搏器的作用。因此，P. terraenovae也是一个很好的模式物种，与D. melanogaster平行。在D. melanogaster中，s-LNvs将昼夜节律信息传递给位于大脑背侧的其他时钟神经元亚群。我们检测了前脑背侧s-LNvs的pdf阳性纤维的突触连接，发现s-LNvs的纤维含有大的密包囊泡（DCVs），以及许多小的透明囊泡，这些囊泡形成发散的输出突触，连接到非神经突上。此外，三维重建显示s-LNvs纤维上存在输入突触。这些结果表明，除了通过突触输出或旁分泌释放DCV内容提供s-LNvs的双重输出的结构特征外，s-LNvs在背侧大脑中接受直接的突触输入。在P. terraenovae中，我们证明了副延髓中Pt-PDF/LNs的纤维接收来自视网膜外光感受器终端的输入突触，称为“Pt-eyelets”。此外，在背侧的原大脑中，我们发现Pt-PDF/LNs的纤维在位于侧部的PL神经元上形成输出突触，这对于诱导生殖滞育是必不可少的。这些结果表明，Pt-PDF/LNs将pt孔检测到的光信息传递给PL神经元，它们可能在时间测量系统中发挥一定的作用，并将处理后的信息传递给PL神经元。我们的研究结果首次揭示了生物钟神经回路的一些基本特征。少

To unravel the wiring of the circadian pacemaker networks underlying rhythmic locomotor activity, we surveyed the pre-and post-synaptic neural elements of the circadian pacemaker neurons, using Drosophila melanogaster and Protophormia terraenovae as model organisms. P. terraenovae has PDF (pigment dispersing factor)-immunopositive neurons (called here Pt-PDF/LNs), corresponding to the Drosophila PDF-immunopositive s-LNvs (small ventral lateral neurons) that function as circadian pacemakers. Therefore, P. terraenovae is also a good model species, paralleling D. melanogaster.In D. melanogaster, the s-LNvs transmit circadian information to the subsets of other clock neurons located in the dorsal protocerebrum of the brain. We examined the synaptic connections of the PDF-positive fibers of s-LNvs in the dorsal protocerebrum, and found that the fibers of s-LNvs contain large dense-cored vesicles (DCVs), as well as numerous small clear vesicles which form divergent output synapses onto unlab … More eled neurites. In addition, three-dimensional reconstruction revealed the presence of input synapses onto the s-LNvs fibers. These results indicate that the s-LNvs receive direct synaptic input in the dorsal protocerebrum, besides exhibiting structural features for supplying the dual outputs from the s-LNvs, either via synaptic outputs or via paracrine release of DCV contents. In P. terraenovae, we demonstrated that the fibers of Pt-PDF/LNs in the accessory medulla receive input synapses from the terminals of extraretinal photoreceptors called 'Pt-eyelets'. Furthermore, in the dorsal protocerebrum, we showed that the fibers of Pt-PDF/LNs form output synapses onto the PL neurons, which locate in the pars lateralis and are indispensable for the induction of reproductive diapause. These results indicate that Pt-PDF/LNs convey the light information detected by the Pt-eyelet to the PL neurons, and that they might play some roles in the time-measurement system and in sending processed information to the PL neurons. Our results provided the first insight into some basic characteristics of the clock's neural circuits. Less