Understanding the role of the NMDA receptor subunit, GluN2D, in mediating NMDA receptor antagonist-induced behavioral disruptions in male and female mice.

Blocking NMDA receptors with drugs like PCP and ketamine causes psychosis-like symptoms in humans and hyperlocomotion in rodents. Mice lacking the GluN2D subunit of the NMDA receptor show reduced hyperlocomotion in response to these drugs, suggesting this subunit is key for that effect. This study tested male and female mice lacking GluN2D and found they also had blunted locomotor responses to PCP, S-ketamine, and R-norketamine, in both sexes. These knockout mice showed an anxious baseline, and the drugs had anxiolytic effects that varied by sex and genotype. S-ketamine disrupted spatial memory in females and object recognition in both sexes, regardless of genotype. The GluN2D subunit mediates sex-specific and drug-specific behavioral effects of NMDA receptor antagonists.

Study at a glance

Abstract

Noncompetitive NMDA receptor (NMDAR) antagonists like phencyclidine (PCP) and ketamine cause psychosis-like symptoms in healthy humans, exacerbate schizophrenia symptoms in people with the disorder, and disrupt a range of schizophrenia-relevant behaviors in rodents, including hyperlocomotion. This is negated in mice lacking the GluN2D subunit of the NMDAR, suggesting the GluN2D subunit mediates the hyperlocomotor effects of these drugs. However, the role of GluN2D in mediating other schizophrenia-relevant NMDAR antagonist-induced behavioral disturbances, and in both sexes, is unclear. This study aimed to investigate the role of the GluN2D subunit in mediating schizophrenia-relevant behaviors induced by a range of NMDA receptor antagonists. Using both male and female GluN2D knockout (KO) mice, we examined the effects of the NMDAR antagonist's PCP, the S-ketamine enantiomer (S-ket), and the ketamine metabolite R-norketamine (R-norket) on locomotor activity, anxiety-related behavior, and recognition and short-term spatial memory. GluN2D-KO mice showed a blunted locomotor response to R-norket, S-ket, and PCP, a phenotype present in both sexes. GluN2D-KO mice of both sexes showed an anxious phenotype and S-ket, R-norket, and PCP showed anxiolytic effects that were dependent on sex and genotype. S-ket disrupted spatial recognition memory in females and novel object recognition memory in both sexes, independent of genotype. This datum identifies a role for the GluN2D subunit in sex-specific effects of NMDAR antagonists and on the differential effects of the R- and S-ket enantiomers.