Changes in subunit composition of NMDA receptors in animal models of schizophrenia by repeated administration of methamphetamine
PROGRESS IN NEURO-PSYCHOPHARMACOLOGY & BIOLOGICAL PSYCHIATRY
Authors: Oka, Matsuhiko; Ito, Koki; Koga, Minori; Kusumi, Ichiro
Abstract
The dopamine and glutamate hypotheses reflect only some of the pathophysiological changes associated with schizophrenia. We have proposed a new comprehensive progressive pathophysiology model based on the dopamine to glutamate hypothesis. Repeated administration of methamphetamine (METH) at a dose of 2.5mg/kg in rats has been used to assess dynamic changes in the pathophysiology of schizophrenia. Previous use of this model suggested N-methyl-d-aspartate receptor (NMDA-R) dysfunction, but the mechanism could only be inferred from limited, indirect observations. In the present study, we used this model to investigate changes in the expression of NMDA-R subunits. Repeated administration of METH significantly decreased the gene expression levels of glutamate ionotropic receptor NMDA type subunit (Grin) subtypes Grin1 and Grin2c in the prefrontal cortex (PFC), Grin1 and Grin2a in the hippocampus (HPC), and Grin1, Grin2b, and Grin2d in the striatum (ST).We observed a significant difference in Grin1 expression between the PFC and ST. Furthermore, repeated administration of METH significantly decreased the protein expression of GluN1 in both cytosolic and synaptosomal fractions isolated from the PFC, and significantly decreased the protein expression of GluN1 in the cytosolic fraction, but not the synaptosomal fraction from the ST. These regional differences may be due to variations in the synthesis of GluN1 or intracellular trafficking events in each area of the brain. Considering that knockdown of Grin1 in mice affects vulnerability to develop schizophrenia, these results suggest that this model reflects some of the pathophysiological changes of schizophrenia, combining both the dopamine and glutamate hypotheses.
Glutamate Genetics in Obsessive-Compulsive Disorder: A Review
JOURNAL OF THE CANADIAN ACADEMY OF CHILD AND ADOLESCENT PSYCHIATRY
Authors: Rajendram, Rageen; Kronenberg, Sefi; Burton, Christie L.; Arnold, Paul D.
Abstract
Objective: Obsessive-compulsive disorder (OCD) is common and debilitating with patients exhibiting persistent intrusive thoughts (obsessions), repetitive ritualistic behaviours (compulsions) and anxiety. While it is known that OCD is highly heritable, the specific genetic risk factors for OCD are still largely unknown. The etiology of OCD has also not been fully elucidated but there is growing evidence that glutamate signaling dysfunction in the cortico-striatal-thalamo-cortical (CSTC) circuitry plays a role in its pathogenesis. Methods: We conducted a focused review of recent literature on the role of glutamate genes in OCD. Results: There have been several recent discoveries in the SAPAP (DLGAP) family, SLC1A1, and GRIN/GRIK families of proteins related to OCD. Conclusion: There is growing evidence supporting a role for genetic variation leading to dysfunctional glutamate signaling in OCD. Based on this new evidence we hypothesize that sustained glutamatergic neurotransmission in key areas of the brain may be contributing to the etiology of OCD.