Abstract: Disclosed are negative allosteric modulators of GluN3-containing NMDA receptors. In general, these compounds are highly selective for GluN3 (such as GluN3A and/or GluN3B) over GluN1 and/or GluN2. They can function as non-competitive antagonists with activity that is independent of membrane potential, glycine concentration, and extracellular pH. Also disclosed are pharmaceutical formulations of the negative allosteric modulators. These compounds can be used to enhance synaptic function and/or treating a neurological condition or disorder. Exemplary neurological conditions or disorders include, but are not limited to, major mental disorders, conditions that involve basal ganglia or altered dopamine, substance abuse/addiction or predisposition to substance abuse/addiction, pain disorders, developmental delay or situations with impaired learning, memory, and/or cognition, acute neuronal or glial injuries, and circuit disorders.