A02

Role of plasticity at hippocampal output synapses in memory

The subiculum is the output region of the multi-synaptic hippocampal circuit and plays an important role in memory. Pyramidal cells in the subiculum are functionally heterogeneous and active during high-frequency “sharp-wave ripples” oscillations that are propagated from the subiculum via the retrosplenial cortex for long-term memory consolidation. Within the hippocampal circuit two synaptic connections – dentate gyrus (DG) to CA3 and CA1-subiculum – express a form of long-term plasticity that is cAMP dependent and is induced and expressed presynaptically. We found that, at DG-CA3 synapses, cAMP increase triggers a reorganization of synaptic vesicles leading to an increase in the number of docked vesicles belonging to the readily releasable pool (RRP). The increase in vesicle availability could be a mechanism for synaptic long-term potentiation and might be important also to gate information transfer out of the hippocampus at CA1-subiculum connections. We aim to test whether structural presynaptic plasticity at CA1-to-distal subiculum synapses is necessary for memory stabilizations.

Image credit: Rost9 Magnific.com

Archive – A02 (SFB1315/1)

Archive – A02 (SFB1315/2)

Graphical Abstract

Graphical Abstract Top left: output hippocampal circuit from CA1 (yellow) to proximal subiculum (grey) and distal subiculum (purple), and from there to the cortex. Top middle: zoom in into the subiculum (SUB) with proximal pyramidal cells (grey) and vGLUT2-positive distal pyramidal cells (purple). Top right: radial arm maze behavioral paradigm with tracked trajectories to goal arm (correct trajectory in blue, goal arm in green). Bottom left: synaptic connection between CA1 and distal SUB neurons. Bottom middle: optogenetic strategy with a fusion protein of vesicular protein synaptophysin (blue line, vesicle in grey) and bPAC (photoactivated adenylyl cyclase). Bottom right – optogenetically potentiated synapse from CA1 to SUB

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