Chaverra Martha, Toney John Paul, Dardenne-Ankringa Lizetta D, Knee Jace Tolleson, Morris Ann R, Wadhams Joseph B, Certel Sarah J, Stowers R Steven
Montana State University, Department of Microbiology and Cell Biology, Bozeman, MT 59717.
The University of Montana, Division of Biological Sciences, Missoula, MT 59812.
bioRxiv. 2025 Jul 28:2025.07.23.666348. doi: 10.1101/2025.07.23.666348.
The essential outcome of a successful mating is the transfer of genetic material from males to females in sexually reproducing animals from insects to mammals. In males, this culminates in ejaculation, a precisely timed sequence of organ contractions driven by the concerted activity of interneurons, sensory neurons, and motor neurons. Although central command circuits that trigger copulation have been mapped, the motor architecture and the chemical logic that couple specific neuronal subclasses to organ specific contractility, seminal fluid secretion, and sperm emission remain largely uncharted. This gap in knowledge limits our ability to explain how neural circuits adapt to varying contexts and how their failure contributes to infertility. Here we present an in-depth anatomical and functional analysis of the motor neurons that innervate the internal male reproductive tract of Drosophila melanogaster. We identify two classes of multi-transmitter motor neurons based on neurotransmitter usage, namely octopamine and glutamate neurons (OGNs) and serotonin and glutamate neurons (SGNs), each with a biased pattern of innervation: SGNs predominate in the accessory glands, OGNs in the ejaculatory duct, with equal contributions of each to the seminal vesicles. Both classes co-express vesicular transporters for glutamate (vGlut) and amines (vMAT), confirming their dual chemical identity. Their target organs differentially express receptors for glutamate, octopamine, and serotonin, suggesting combinatorial neuromodulation of contractility. Functional manipulations show that SGNs are essential for male fertility but OGNs are dispensable. Glutamatergic transmission from both classes is also dispensable for fertility. These findings provide the first high-resolution map linking multi-transmitter motor neurons to specific reproductive organs, reveal an unexpected division of labor between serotonergic and octopaminergic signaling pathways, and establish a framework for dissecting conserved neural principles that govern ejaculation and male fertility.
在从昆虫到哺乳动物的有性生殖动物中，成功交配的关键结果是遗传物质从雄性转移到雌性。在雄性中，这最终导致射精，这是一个由中间神经元、感觉神经元和运动神经元协同活动驱动的精确计时的器官收缩序列。尽管触发交配的中枢控制回路已被绘制出来，但将特定神经元亚类与器官特定收缩性、精液分泌和精子排放相联系的运动结构和化学逻辑在很大程度上仍未被探索。这一知识空白限制了我们解释神经回路如何适应不同环境以及它们的故障如何导致不育的能力。在这里，我们对支配黑腹果蝇雄性内部生殖道的运动神经元进行了深入的解剖学和功能分析。我们根据神经递质的使用情况确定了两类多递质运动神经元，即章鱼胺和谷氨酸能神经元（OGNs）以及5-羟色胺和谷氨酸能神经元（SGNs），每一类都有偏向性的支配模式：SGNs在附腺中占主导，OGNs在射精管中占主导，二者对精囊的支配作用相当。这两类神经元都共同表达谷氨酸（vGlut）和胺类（vMAT）的囊泡转运体，证实了它们的双重化学特性。它们的靶器官差异表达谷氨酸、章鱼胺和5-羟色胺的受体，提示存在对收缩性的组合神经调节。功能操作表明，SGNs对雄性生育能力至关重要，而OGNs则是可有可无的。来自这两类神经元的谷氨酸能传递对生育能力也是可有可无的。这些发现提供了第一张将多递质运动神经元与特定生殖器官联系起来的高分辨率图谱，揭示了5-羟色胺能和章鱼胺能信号通路之间意想不到的分工，并建立了一个剖析控制射精和雄性生育能力的保守神经原理的框架。
