Inhibition of GluN2B-containing NMDA receptors in early life combined with social stress in adulthood leads to alterations in prefrontal PNNs in mice.

Abstract

Perineuronal nets (PNNs) are specialized extracellular matrix (ECM) structures present in the central nervous system (CNS) and have been identified as significant regulators of developmental plasticity in the developing cortex. PNNs are particularly enriched in the cortex surrounding parvalbumin-expressing (PV⁺) cells. A growing body of evidence suggests that the abnormalities in PV⁺ neurons and PNNs are associated with various neurological disorders, including schizophrenia, which is a neurodevelopmental defect disease. The N-methyl-D-aspartate receptor (NMDAR) selective antagonist is frequently employed to establish animal models of schizophrenia in laboratory settings. The crucial involvement of GluN2B-containing NMDARs in the development of CNS has been extensively established. However, the role of GluN2B in the pathophysiology of schizophrenia has yet to be thoroughly investigated. The present study inhibited GluN2B function through intraperitoneal infusion of the GluN2B selective antagonist ifenprodil into juvenile mice aged 3-4 weeks, followed by the administration of social stress when these mice reached 9 weeks of age. Then, immunofluorescence staining was employed to examine the changes in the PNNs and PV⁺ cells, an acoustic startle and prepulse inhibition test was used to detect activities of the PV⁺ cells, and Western blot was used to quantify the protein expression levels of GluN2A and GluN2B in the prefrontal cortex (PFC). The study revealed that in the PFC of mice subjected to GluN2B antagonist treatment in early life and social stress in adulthood, there was an increase in the number of PV⁺ cells wrapped by PNNs, and a decrease in the activation of PV⁺ cells during the prepulse inhibition test, which is an indicator of sensory gating functions, as well as changes in the protein expression levels of GluN2A and GluN2B, which resulted in an increase in the ratio of GluN2A to GluN2B. These aberrations in the mice are comparable to those observed in animal models and patients with schizophrenia. The findings suggest that even a transient hypofunction of GluN2B in early life poses a significant risk for the emergence of schizophrenia symptoms in adulthood.