Input-specific NMDA receptor function in thalamocortical neurons

Molecular and functional synapse diversity is generated, in part, by differential expression of neurotransmitter receptors and associated macromolecular complexes. N -methyl- D -aspartate receptors (NMDARs) are tetrameric ionotropic glutamate receptors that most often comprise two GluN1 and two GluN2 subunits. Cell-type-specific expression of GluN2 subunits (GluN2A – 2D), which have vastly different properties, generate functionally diverse synapses across neuron populations. Diverse NMDAR function has also been observed at anatomically distinct inputs to a single neuron population. However, prior research has primarily focused on synapse-specific function of only GluN2A and GluN2B subunits. Furthermore, the mechanisms that generate input-specific NMDAR function remain unknown as few studies have visualized subcellular GluN2 subunit localization in native brain tissue. We investigated NMDAR synaptic localization and function in thalamocortical (TC) neurons expressing all four GluN2 subunits. Utilizing high-resolution imaging and input-specific electrophysiology, we revealed subtype- and input-specific GluN2 localization and function at corticothalamic (CT) versus sensory inputs to TC neurons in 4-week-old male and female C57Bl/6J mice. GluN2B was the most abundant postsynaptic NMDAR subunit across all glutamatergic synapses followed by GluN2A and GluN2C, and GluN2D was localized to the fewest synapses. GluN2B mediated the majority of CT synaptic responses, while GluN2A preferentially mediated sensory synaptic responses. GluN2C and GluN2D contributed to both CT and sensory inputs, but GluN2C showed preferential localization to sensory synapses over CT synapses. This work indicates that TC neurons exhibit subtype- and input-specific localization of diverse NMDARs and associated scaffolding proteins that contribute to functional differences between CT and sensory synapses. This work was supported by funding from the National Institutes of Health (NS105804 and NS128635) and CURE Epilepsy. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.