Glutamate delta-1 receptors regulate a novel tonic excitatory conductance in the mouse bed nucleus of the stria terminalis and influence neuronal function

The plasticity of ionotropic receptors (mainly AMPARs and NMDARs) within the glutamatergic system has long been investigated as a mechanism for physiological and pathological adaptive learning. The tetrameric delta glutamate receptors (δGluRs, GluD1 and GluD2) are homologs of the AMPARs and NMDARs, however they are insensitive to glutamate. These proteins, especially GluD1, have been implicated in multiple psychiatric conditions and play a functional role in synapses assembly and stability, but recent evidence suggests they also may supply a tonic excitatory conductance, are sensitive to poly-amine blockade, and regulate synaptic plasticity. Here we use whole-cell patch clamp electrophysiology to functionally characterize these receptors in the dorsolateral bed nucleus of the stria terminalis (dlBNST) and investigate their modulation of both synaptic transmission and cell excitability. Our results suggest that δGluRs, and in particular GluD1, carry a tonic conductance, modulate excitatory synapses, and regulate cell excitability in the dlBNST. These results imply that GluD1 functions to regulate the flow of information through the BNST and may play a role in affect, stress, and substance use disorders.