Guangdong-Hongkong-Macau Institute of CNS Regeneration, Ministry of Education CNS Regeneration Collaborative Joint Laboratory, Jinan University, Guangzhou 510632, China.
Guangdong key Laboratory of Brain Function and Diseases, Jinan University, Guangzhou 510632, China.
Nat Commun. 2017 Mar 31;8:14908. doi: 10.1038/ncomms14908.
Animals promote their survival by avoiding rapidly approaching objects that indicate threats. In mice, looming-evoked defensive responses are triggered by the superior colliculus (SC) which receives direct retinal inputs. However, the specific neural circuits that begin in the retina and mediate this important behaviour remain unclear. Here we identify a subset of retinal ganglion cells (RGCs) that controls mouse looming-evoked defensive responses through axonal collaterals to the dorsal raphe nucleus (DRN) and SC. Looming signals transmitted by DRN-projecting RGCs activate DRN GABAergic neurons that in turn inhibit serotoninergic neurons. Moreover, activation of DRN serotoninergic neurons reduces looming-evoked defensive behaviours. Thus, a dedicated population of RGCs signals rapidly approaching visual threats and their input to the DRN controls a serotonergic self-gating mechanism that regulates innate defensive responses. Our study provides new insights into how the DRN and SC work in concert to extract and translate visual threats into defensive behavioural responses.
动物通过避免接近可能带来威胁的快速移动的物体来促进自身的生存。在老鼠中，由上丘（SC）触发的逼近诱发防御反应，而上丘接收直接的视网膜输入。然而，起始于视网膜并介导这种重要行为的特定神经回路仍不清楚。在这里，我们鉴定出一小部分视网膜神经节细胞（RGCs），它们通过轴突侧支到中缝背核（DRN）和 SC 来控制老鼠的逼近诱发防御反应。由投射到 DRN 的 RGCs 传递的逼近信号激活 DRN GABA 能神经元，进而抑制 5-羟色胺能神经元。此外，激活 DRN 5-羟色胺能神经元会减少逼近诱发的防御行为。因此，一组特定的 RGCs 会发出快速接近视觉威胁的信号，它们对 DRN 的输入控制着一种 5-羟色胺能的自我门控机制，调节先天的防御反应。我们的研究为 DRN 和 SC 如何协同工作，将视觉威胁提取并转化为防御行为反应提供了新的见解。
