Morphologycal analysses of the neural components of the input and output pathways involved in the Drosophila circadian system, with special reference to the cholinergic neurons.

在嗜龙动物中，各种各样的证据表明，日常运动节律的昼夜节律起搏器位于髓质前皮层的“侧神经元”（LNs）细胞中。然而，人们对这些起搏器细胞与行为节律之间的神经通路知之甚少。为了确定果蝇生物钟系统输入和输出通路的神经成分，我们使用免疫细胞化学技术对大脑进行了调查，特别是参考了胆碱能神经元。针对果蝇胆碱乙酰转移酶（ChAT）的单克隆抗体染色复眼后缘的一组视网膜外光感受器，称为“眼”。从小孔中伸出的轴突终止于前髓质区域，那里可能存在神经元的树突区。LNs对一种针对果蝇nAChR的抗体有免疫反应，这表明LNs有胆碱能输入。这一间接证据表明，小孔处的More参与了促进昼夜节律干扰的输入通路。携带含有1.2 kb顺式调控序列的ChAT cDNA的转基因转化蝇，在胆碱能神经元的特定亚群中，如在髓质远端终止的神经元中，ChAT的表达明显降低，髓质远端是神经元输出纤维曲张的地方。一项形态计量学研究显示，与野生型果蝇相比，转化型果蝇的髓质LN静脉曲张明显更大。与对照蝇（白色）一样，变形蝇也经历了光明和黑暗周期，并表现出带有早晚高峰的双峰运动活动模式。当光照水平较低（即0.24勒克斯）时，变形体表现出不寻常的单食运动活动，只发生在整个光照阶段，而对照组则出现双峰活动。这些观察结果表明，在转化体中，ChAT表达缺陷导致了异常的运动节律。少

In Drasophila, various lines of evidence suggest that the circadian pacemakers for daily locomotor rhythms reside in the cells called "lateral neurons" (LNs) lying in the anterior rind of the medulla. However, little is known about the neural pathways linking these pacemaker cells to behavioral rhythms. To identify the neural components of the input and output pathways of the Drosophila circadian clock system, we have surveyed the brain using immunocytochemical techniques, especially with reference to cholinergic neurons. A monoclonal antibody against Drosophila choline acetyltransferase (ChAT) stained a group of extraretinal photoreceptors at the posterior margin of the compound eye, which is called the "eyelet". The axons emerging from the eyelet terminated in the region of the anterior medulla, where the possible dendritic field of LNs resides. LNs were immunoreactive to an antibody against Drosophila nAChR, implying cholinergic input to LNs. This circumstantial evidence suggests th … More at the eyelet is involved in an input pathway contributing to circadian entrainment. Transformed flies carrying the transgene composed of ChAT cDNA with 1.2 kb of the cis-regulatory sequence showed obviously reduced ChAT expression in specific subsets of cholinergic neurons, such as the neurons terminating in the distal region of the medulla, where the varicosity of the output fibers of LNs resides. A morphometric study revealed that LN varicosity in the medulla was -significantly larger in the transformants than in the wild-type flies. The transformants entrained to light : dark cycles, and exhibited a double-peaked locomotor activity pattern with morning and evening peaks, as did control flies (white). When the illumination level was low (I.e., 0.24 lux), the transformants showed unusual monophagic locomotor activity exclusively occurring during the entire light phase, in contrast to double-peaked activity in the controls. These observations suggest that defects in ChAT expression resulted in the extraordinary locomotor rhythms in the transformants. Less