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Wang CC, Held RG, Chang SC, Yang L, Delpire E, Ghosh A, Hall BJ. A Critical Role for GluN2B-Containing NMDA Receptors in Cortical Development and Function. Neuron. 2011 Dec 8 ; 72(5):789-805. Pubmed Abstract

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Comment by:  Stefan KolataKazu Nakazawa
Submitted 21 February 2012
Posted 21 February 2012

The original NMDA receptor (NMDAR) hypofunction theory of schizophrenia was predicated on the discovery that, in adulthood, NMDAR antagonists mimicked disease symptomatology and exacerbated symptoms in schizophrenic patients (Javitt and Zukin, 1991). Recent advances have since shown that, in addition to this effect in adulthood, there may be a postnatal developmental sensitive period necessary for NMDAR hypofunction to later manifest as schizophrenia phenotypes. For instance, in mice, schizophrenia-like phenotypes were observed when NR1 (GluN1) was ablated selectively in corticolimbic interneurons after postnatal day 7, but not when the knockout occurred after adolescence (Belforte et al., 2010). Similarly, transient antagonism of NMDA during development later resulted in schizophrenia-like phenotypes in adult rats (Stefani and Moghaddam, 2005; Baier et al., 2009). In the present work by Wang et al. (2011), using an elegant molecular genetic technique, Benjamin Hall and his colleagues were able to show that it is perhaps the NR2B (GluN2B) subunit during this developmental period that is most critical for the later development of the symptomatology. NR2B is highly expressed during this postnatal sensitive period, and is only later replaced by NR2A (GluN2A) in most NMDA receptors. The present paper showed that an early replacement of NR2B with NR2A recapitulated some of the NMDA hypomorph phenotypes. While these results are very intriguing and dovetail nicely with the emerging thinking about the neurodevelopmental role of NMDARs, the possible involvement of NR2A itself in schizophrenia should not be lost. Impairment of NR2A results in several schizophrenia-like phenotypes, including a reduction in parvalbumin immunoreactivity, impaired fast-spiking interneuron maturation, altered dopamine metabolism, and a hyperlocomotion response in the open field that is rescued by antipsychotic treatment (Zhang and Sun, 2011; Miyamoto et al., 2001). Further studies of synapses, neurons, and neuronal networks regulated by NR2A and NR2B may lead to a better understanding of the mechanisms underlying the NMDAR hypofunction theory of schizophrenia.

References:

Baier PC, Blume A, Koch J, Marx A, Fritzer G, Aldenhoff JB, Schiffelholz T. Early postnatal depletion of NMDA receptor development affects behaviour and NMDA receptor expression until later adulthood in rats--a possible model for schizophrenia. Behav Brain Res. 2009 Dec 14;205(1):96-101. Abstract

Belforte JE, Zsiros V, Sklar ER, Jiang Z, Yu G, Li Y, Quinlan EM, Nakazawa K. Postnatal NMDA receptor ablation in corticolimbic interneurons confers schizophrenia-like phenotypes. Nat Neurosci. 2010 Jan;13(1):76-83. Abstract

Javitt DC, Zukin SR. Recent advances in the phencyclidine model of schizophrenia. Am J Psychiatry. 1991 Oct;148(10):1301-8. Abstract

Miyamoto Y, Yamada K, Noda Y, Mori H, Mishina M, Nabeshima T. Hyperfunction of dopaminergic and serotonergic neuronal systems in mice lacking the NMDA receptor epsilon1 subunit. J Neurosci. 2001 Jan 15;21(2):750-7. Abstract

Stefani MR, Moghaddam B. Transient N-methyl-D-aspartate receptor blockade in early development causes lasting cognitive deficits relevant to schizophrenia. Biol Psychiatry. 2005 Feb 15;57(4):433-6. Abstract

Zhang Z, Sun QQ. Development of NMDA NR2 subunits and their roles in critical period maturation of neocortical GABAergic interneurons. Dev Neurobiol. 2011 Mar;71(3):221-45. Abstract

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