Mammalian hearing depends on sound-evoked displacements of the stereocilia of inner hair cells (IHCs), which cause the endogenous mechanoelectrical transducer channels to conduct inward currents of cations including Ca²⁺. Due to their presumed lack of contacts with the overlaying tectorial membrane (TM), the putative stimulation mechanism for these stereocilia is by means of the viscous drag of the surrounding endolymph. However, despite numerous efforts to characterize the TM by electron microscopy and other techniques, the exact IHC stereocilia-TM relationship remains elusive. Here we show that Ca²⁺-rich filamentous structures, that we call Ca²⁺ ducts, connect the TM to the IHC stereocilia to enable mechanical stimulation by the TM while also ensuring the stereocilia access to TM Ca²⁺. Our results call for a reassessment of the stimulation mechanism for the IHC stereocilia and the TM role in hearing.

哺乳动物的听力取决于内毛细胞 (IHC) 静纤毛的声音诱发位移，这会导致内源性机械电换能器通道传导包括 Ca ²⁺在内的阳离子的内向电流。由于假定它们与覆盖的盖膜 (TM) 缺乏接触，这些静纤毛的假定刺激机制是通过周围内淋巴的粘性阻力。然而，尽管通过电子显微镜和其他技术对 TM 进行了大量努力，但确切的 IHC 静纤毛-TM 关系仍然难以捉摸。在这里我们展示了富含Ca ^{2+ 的}丝状结构，我们称之为 Ca ²⁺导管，将 TM 连接到 IHC 静纤毛，以通过 TM 实现机械刺激，同时确保静纤毛获得 TM Ca ²⁺。我们的结果要求重新评估 IHC 静纤毛的刺激机制和 TM 在听力中的作用。