Stimulation induces gradual increases in the thickness and curvature of postsynaptic density of hippocampal CA1 neurons in slice cultures

Jung-Hwa Tao-Cheng

doi:10.1186/s13041-019-0468-x

Abstract

Activity can induce structural changes in glutamatergic excitatory synapses, including increase in thickness and curvature of the postsynaptic density (PSD); these structural changes can only be documented by electron microscopy. Here in organotypic hippocampal slice cultures where experimental conditions can be easily manipulated, increases in thickness and curvature of PSDs were noticeable within 30 s of stimulation and progressed with time up to 3 min. These structural changes were reversible upon returning the samples to control medium for 5–10 min. Thus, the postsynaptic density is a very dynamic structure that undergoes rapid reorganization of its components upon stimulation, and recovery upon cessation of stimulation. The gradual increase in thickness of PSD could result from a gradual translocation of some PSD proteins to the PSD, and the increase in curvature of the PSD is likely led by postsynaptic elements.

Highlights

The postsynaptic density (PSD) appears as dark material ~ 30 nm thick under the postsynaptic membrane in glutamatergic excitatory synapses of mammalian central nervous system by electron microscopy (EM)
The PSD can be subdivided into two layers: (1) the PSD core, a layer close to the postsynaptic membrane that is relatively stable either under basal or stimulated conditions, and (2) the PSD “pallium”, a deeper layer that is contiguous with the PD core, but extending further into the cytoplasm
Stimulation increased the thickness and curvature of the postsynaptic density In control samples under basal conditions, the PSD appeared as a thin layer of dark material approximately 30–40 nm from the postsynaptic membrane (Fig. 1a)

Summary

Introduction

The postsynaptic density (PSD) appears as dark material ~ 30 nm thick under the postsynaptic membrane in glutamatergic excitatory synapses of mammalian central nervous system by electron microscopy (EM). The PSD can be subdivided into two layers: (1) the PSD core, a layer close to the postsynaptic membrane that is relatively stable either under basal or stimulated conditions, and (2) the PSD “pallium”, a deeper layer that is contiguous with the PD core, but extending further into the cytoplasm It is this deeper layer of the PSD that becomes darker upon stimulation [3], and gives the appearance of PSD thickening. Stimulation-induced thickening of PSD has been reported in dissociated hippocampal neuronal cultures [5,6,7], and in organotypic slice cultures of the hippocampus [8, 9] These studies only compared PSDs under control basal conditions vs those under intense excitatory stimulation

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Conclusion