Synapse-specific and plasticity-regulated AMPA receptor mobility tunes synaptic integration

Synaptic responses adapt on millisecond-to-second timescales through short-term plasticity (STP), a key process that filters and transforms neuronal information. While STP is classically ascribed to presynaptic release mechanisms, postsynaptic receptor properties-particularly desensitization and surface diffusion-also shape synaptic responses. Here, we dissect pre- and postsynaptic contributions to synaptic adaptation using molecular tools to visualize glutamate release and manipulate AMPA receptor (AMPAR) diffusion in intact circuits. We find that synaptic gain during STP is tuned by synapse-specific regulation of AMPAR biophysics and diffusion-trapping. These features are determined constitutively by auxiliary subunit profiles and dynamically by activity-dependent signaling engaged during long-term plasticity. With modeling, we quantified how short-term synaptic dynamics are impacted by postsynaptic regulation of filtering properties, which broadened heterogeneity of filtering timescales to refine temporal selectivity in synaptic networks. By augmenting desensitization-mediated synaptic depression, AMPAR diffusion-trapping emerges as a fundamental regulatory mechanism of postsynaptic integration and circuit-level information processing.