Animal brains have discrete circadian neurons, but little is known about how they are coordinated to influence and maintain sleep. Here, through a systematic optogenetic screening, we identified a subtype of uncharacterized circadian DN3 neurons that is strongly sleep promoting in Drosophila. These anterior-projecting DN3s (APDN3s) receive signals from DN1 circadian neurons and then output to newly identified noncircadian “claw” neurons (CLs). CLs have a daily Ca²⁺ cycle, which peaks at night and correlates with DN1 and DN3 Ca²⁺ cycles. The CLs feedback onto a subset of DN1s to form a positive recurrent loop that maintains sleep. Using trans-synaptic photoactivatable green fluorescent protein (PA-GFP) tracing and functional in vivo imaging, we demonstrated that the CLs drive sleep by interacting with and releasing acetylcholine onto the mushroom body γ lobe. Taken together, the data identify a novel self-reinforcing loop within the circadian network and a new sleep-promoting neuropile that are both essential for maintaining normal sleep.

动物的大脑具有离散的昼夜节律神经元，但人们对它们如何协调以影响和维持睡眠知之甚少。在这里，通过系统的光遗传学筛查，我们确定了一种在果蝇中具有强烈睡眠促进作用的未表征的昼夜节律 DN3 神经元亚型。这些向前突出的 DN3 (APDN3) 接收来自 DN1 昼夜节律神经元的信号，然后输出到新发现的非昼夜节律“爪”神经元 (CL)。CLs 有一个每日 Ca ²⁺循环，在夜间达到峰值并与 DN1 和 DN3 Ca ²⁺循环相关。CL 反馈到 DN1 的一个子集，以形成一个维持睡眠的正循环循环。使用反式突触光激活绿色荧光蛋白 (PA-GFP) 示踪和功能在体内成像中，我们证明了 CL 通过与乙酰胆碱相互作用并将其释放到蘑菇体 γ 叶上来驱动睡眠。总之，这些数据确定了昼夜节律网络中一个新的自我强化循环和一个新的促进睡眠的神经细胞，这两者对于维持正常睡眠都是必不可少的。