In Vivo Imaging of Dentate Gyrus Mossy Cells in Behaving Mice

Abstract

Summary Mossy cells in the hilus of the dentate gyrus constitute a major excitatory principal cell type in the mammalian hippocampus, however, it remains unknown how these cells behave in vivo. Here, we have used two-photon Ca2+ imaging to monitor the activity of mossy cells in awake, behaving mice. We find that mossy cells are significantly more active than dentate granule cells in vivo, exhibit spatial tuning during head-fixed spatial navigation, and undergo robust remapping of their spatial representations in response to contextual manipulation. Our results provide the first characterization of mossy cells in the behaving animal and demonstrate their active participation in spatial coding and contextual representation.

Mossy Cells Control Adult Neural Stem Cell Quiescence and Maintenance through a Dynamic Balance between Direct and Indirect Pathways

“…MC are known to strongly respond to spatial exploration (Danielson et al, 2017). We therefore continuously exposed adult Nestin-GFP mice to enriched environment (EE) for 13 days.…”

“…Recent in vivo electrophysiology and intrinsic calcium imaging studies convincingly link unique MC circuits and properties to pattern separation (Danielson et al, 2017; GoodSmith et al, 2017; Senzai and Buzsaki, 2017). However, how MCs might contribute to the regulation of adult NSCs and hippocampal neurogenesis remains unknown.…”

“…It is worth mentioning that the activation state of MCs is a relative definition that only correlates with the CNO dose used for these experiments. Both in vitro electrophysiology and in vivo calcium imaging analysis has demonstrated that MCs are more active than dentate GCs (Danielson et al, 2017; Scharfman, 1995). The active basal state of MCs was also confirmed by our calcium imaging analysis of 5htr2A-expressing MCs in acute brain slices showing that MCs typically exhibit a high level of spontaneous activity.…”

“…Furthermore, MC loss caused a disinhibition and transient hyperexcitability of GCs (Jinde et al, 2012). Recent modeling data also concluded that deletion of the direct excitatory pathway would had little effect on GC excitability, but deletion of the indirect inhibitory pathways by deleting MC-basket cell connection would significantly increase GC excitability (Danielson et al, 2017). These results together implicate that rNSC activity is a reflection of the dentate network activity.…”

Dentate gyrus mossy cells control spontaneous convulsive seizures and spatial memory

“…MCs have multiple place fields and exhibit stronger place-field remapping than GCs in response to changes in environmental cues (22–24). We demonstrated that MCs are critical in encoding, but not in retrieval, of spatially relevant information.…”