Differential Role of NR2A and NR2B Subunits in N-Methyl-D-Aspartate Receptor Antagonist-Induced Aberrant Cortical Gamma Oscillations

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• 作者：Bernat Kocsis ; ^{bkocsis@hms.harvard.edu}
• 关键词：Glutamate ; ketamine ; MK801 ; neural network ; NMDA hypofunction ; schizophrenia
• 刊名：Biological Psychiatry
• 出版年：2012
• 期刊代码：34_00063223
• 类别：med
• 出版时间：1 June, 2012
• 卷：71
• 期：11
• 页码：987-995
• 文件大小：1673 K

摘要

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Background

N-methyl-D-aspartate receptor (NMDA-R) hypofunction plays an important role in cognitive impairment in schizophrenia. NMDA-R antagonists elicit psychotic symptoms in humans and schizophrenia-relevant signs in rodents, including a strong increase in cortical gamma activity. NMDA-Rs are composed of different subunits, and accumulating evidence indicates that neuronal damage due to NMDA-R antagonists depends on their action on a specific type of the receptor containing the NR2A subunit. In human schizophrenics, NR2A is selectively reduced in fast-firing interneurons. These neurons are critical for gamma oscillations, indicating that pathological changes in gamma activity may depend on subunit-specific NMDA-R deficit. The present study tested this hypothesis.

Methods

Cortical electroencephalograms were recorded in freely moving rats and the changes in gamma power were measured after administration of NMDA-R antagonists with different subunit selectivity, including NR2A-preferring (PEAQX, n = 5; NVP-AAM077, n = 18), NR2B-selective (ifenprodil, n = 6; threo-ifenprodil, n = 4; Ro25-6985, n = 13), and NR2C/D-selective (n = 8) antagonists, along with vehicle and nonselective NMDA-R antagonists (ketamine, n = 10; MK801, n = 12). Changes in prepulse inhibition of startle was tested after MK-801 (n = 6), NVP-AAM077, and Ro-6891 (n = 5) injection.

Results

Strong increase in gamma power was induced by nonselective NMDA-R antagonists and by blockade of NMDA-Rs containing the NR2A subunit, with co-occurring gating deficits and diminished low-frequency modulation of gamma oscillations. In contrast, selective blockade of NR2B, C, or D subunit-containing receptors had minor effects.

Conclusions

Major subtype-specific differences in the role of NMDA-Rs in cortical gamma oscillation may have implications for the pathomechanism and treatment of cognitive impairment in schizophrenia.