Department of Pharmacology, University of North Carolina, Chapel Hill, United States.
Neuroscience Center, University of North Carolina, Chapel Hill, United States.
Elife. 2020 Feb 26;9:e53129. doi: 10.7554/eLife.53129.
The supramammillary nucleus (SuM) provides substantial innervation to the dentate gyrus (DG). It remains unknown how the SuM and DG coordinate their activities at the circuit level to regulate spatial memory. Additionally, SuM co-releases GABA and glutamate to the DG, but the relative role of GABA versus glutamate in regulating spatial memory remains unknown. Here we report that SuM-DG Ca activities are highly correlated during spatial memory retrieval as compared to the moderate correlation during memory encoding when mice are performing a location discrimination task. Supporting this evidence, we demonstrate that the activity of SuM neurons or SuM-DG projections is required for spatial memory retrieval. Furthermore, we show that SuM glutamate transmission is necessary for both spatial memory retrieval and highly-correlated SuM-DG activities during spatial memory retrieval. Our studies identify a long-range SuM-DG circuit linking two highly correlated subcortical regions to regulate spatial memory retrieval through SuM glutamate release.
穹窿下核（SuM）向齿状回（DG）提供大量的神经支配。目前尚不清楚 SuM 和 DG 如何在回路水平上协调它们的活动，以调节空间记忆。此外，SuM 向 DG 共同释放 GABA 和谷氨酸，但 GABA 与谷氨酸在调节空间记忆方面的相对作用尚不清楚。在这里，我们报告说，与小鼠在执行位置辨别任务时进行记忆编码期间的中度相关性相比，在进行空间记忆检索时，SuM-DG Ca 活性高度相关。支持这一证据，我们证明 SuM 神经元或 SuM-DG 投射的活性对于空间记忆检索是必需的。此外，我们还表明，在空间记忆检索期间，SuM 谷氨酸传递对于空间记忆检索和 SuM-DG 活动的高度相关性都是必需的。我们的研究确定了一个长程 SuM-DG 回路，将两个高度相关的皮质下区域连接起来，通过 SuM 谷氨酸释放来调节空间记忆检索。
