Neuronal plasticity affects correlation between the size of dendritic spine and its postsynaptic density

Anna Caly,Kasia Radwanska,Malgorzata Borczyk,Tytus Bernas,Małgorzata Alicja Śliwińska

doi:10.1038/s41598-018-38412-7

Anna Caly, Kasia Radwanska + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-38412-7

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Abstract

Structural plasticity of dendritic spines is thought to underlie memory formation. Size of a dendritic spine is considered proportional to the size of its postsynaptic density (PSD), number of glutamate receptors and synaptic strength. However, whether this correlation is true for all dendritic spine volumes, and remains stable during synaptic plasticity, is largely unknown. In this study, we take advantage of 3D electron microscopy and reconstruct dendritic spines and cores of PSDs from the stratum radiatum of the area CA1 of organotypic hippocampal slices. We observe that approximately 1/3 of dendritic spines, in a range of medium sizes, fail to reach significant correlation between dendritic spine volume and PSD surface area or PSD-core volume. During NMDA receptor-dependent chemical long-term potentiation (NMDAR-cLTP) dendritic spines and their PSD not only grow, but also PSD area and PSD-core volume to spine volume ratio is increased, and the correlation between the sizes of these two is tightened. Further analysis specified that only spines that contain smooth endoplasmic reticulum (SER) grow during cLTP, while PSD-cores grow irrespectively of the presence of SER in the spine. Dendritic spines with SER also show higher correlation of the volumetric parameters than spines without SER, and this correlation is further increased during cLTP only in the spines that contain SER. Overall, we found that correlation between PSD surface area and spine volume is not consistent across all spine volumes, is modified and tightened during synaptic plasticity and regulated by SER.

Highlights

Dendritic spines are small protrusions on neurons that harbour synaptic receptors of excitatory connections
In the current study we ask whether the correlation of postsynaptic density (PSD) and dendritic spine size is an universal phenomenon across all spine sizes and if it is affected by synaptic plasticity and presence of smooth endoplasmic reticulum (SER)
Results chemically-induced long-term potentiation of synaptic transmission (cLTP) is associated with remodelling of dendritic spines and PSD-cores in organotypic hippocampal slice cultures (OHCs)

Summary

Introduction

Dendritic spines are small protrusions on neurons that harbour synaptic receptors of excitatory connections. In the current study we ask whether the correlation of PSD and dendritic spine size is an universal phenomenon across all spine sizes and if it is affected by synaptic plasticity and presence of SER. Toward this end we employed serial block-face scanning electron microscopy (SBEM)[31] to obtain high-resolution, 3D measurements of dendritic spines with PSD-cores in the organotypic hippocampal slices after induction of chemical, NMDAR-dependent long-term potentiation (NMDAR-cLTP)[32]. Our research shows that correlation of PSD surface area and PSD-core volume with dendritic spine volume is not a strict rule and may be affected by the volume of dendritic spine, synaptic plasticity and SER

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