Synaptic Elasticity

Synapses play a critical role in neural circuits, and their highly specialized structures and biochemical characteristics have been widely studied in learning and memory. Along with their role in signal transmission, synapses also serve as adhesion structures, yet their mechanical characteristics have not received much attention. Given the important role of mechanics in cell adhesion, mechanical studies of synapses could offer insights into synaptic development, maintenance, and function. Here, I investigated synaptic elasticity in cultured rat hippocampal neurons and suggest that mechanical elasticity may be related to synaptic plasticity. I used torsional harmonic atomic force microscopy (TH-AFM) to measure the nanomechanical properties of functional mature excitatory synapses, whose identity and activity was verified by fluorescence microscopy. I combined TH-AFM with transmission electron microscopy and found that high stiffness of synapses originated from postsynaptic spines, not presynaptic boutons. I observed that spines at functional mature excitatory synapses were on average 10 times stiffer than dendritic shafts and that the distribution of spine stiffness exhibited a logn