Living Systems Institute, University of Exeter, Exeter, United Kingdom.
Electron Microscopy Core Facility (EMCF), Heidelberg University, Heidelberg, Germany.
Elife. 2024 Sep 19;13:RP94306. doi: 10.7554/eLife.94306.
Hydrostatic pressure is a dominant environmental cue for vertically migrating marine organisms but the physiological mechanisms of responding to pressure changes remain unclear. Here, we uncovered the cellular and circuit bases of a barokinetic response in the planktonic larva of the marine annelid . Increased pressure induced a rapid, graded, and adapting upward swimming response due to the faster beating of cilia in the head multiciliary band. By calcium imaging, we found that brain ciliary photoreceptors showed a graded response to pressure changes. The photoreceptors in animals mutant for had a smaller sensory compartment and mutant larvae showed diminished pressure responses. The ciliary photoreceptors synaptically connect to the head multiciliary band via serotonergic motoneurons. Genetic inhibition of the serotonergic cells blocked pressure-dependent increases in ciliary beating. We conclude that ciliary photoreceptors function as pressure sensors and activate ciliary beating through serotonergic signalling during barokinesis.
静水压力是垂直迁移海洋生物的主要环境线索，但对压力变化做出反应的生理机制仍不清楚。在这里，我们揭示了海洋环节动物浮游幼虫对波动压力反应的细胞和回路基础。由于头部多纤毛带上的纤毛更快地跳动，增加的压力会导致快速、分级和适应的向上游动反应。通过钙成像，我们发现脑纤毛光感受器对压力变化表现出分级响应。对于 突变的动物，感光器的感觉腔更小，突变幼虫的压力反应减弱。纤毛光感受器通过 5-羟色胺能运动神经元与头部多纤毛带突触连接。5-羟色胺能细胞的遗传抑制阻断了纤毛跳动随压力增加的依赖性增加。我们得出结论，纤毛光感受器作为压力传感器，在波动运动期间通过 5-羟色胺能信号激活纤毛跳动。
