Hence, selective positive allosteric modulators (PAMs) of mGlu1 receptors hold promise for the treatment of positive symptoms of schizophrenia. mGlu5 receptors are widely expressed in the CNS and regulate the activity of cells that are involved in the pathophysiology of schizophrenia, such as cortical GABAergic interneurons and microglial cells. mGlu5 receptor PAMs are under development for the treatment of schizophrenia and cater the potential to act as disease modifiers by restraining neuroinflammation. mGlu2 receptors have attracted considerable interest because they negatively modulate 5-HT<sub>2A</sub> serotonin receptor signaling in the cerebral cortex.
In this review, we focus on pharmacological, neurodevelopmental, and genetic animal models of disrupted PPI, with the aim of showing the potential role of mGluR5 in modulating the activity of N-methyl-D-aspartate receptors and their contributions toward the treatment of schizophrenia.
Although the role of the NMDA receptor in cognitive and negative symptoms of schizophrenia is well studied, information about the role of mGluR5 receptors in schizophrenia is sparse.
Our data suggest that neurochemical abnormalities impinging the glutamatergic and GABAergic systems may be responsible for the behavioral phenotype associated with mGlu5 KO animals and point to the close interaction of these molecular players for the development of neuropsychiatric disorders such as schizophrenia.
The objectives of this first-in-human study were to evaluate the safety and tolerability, pharmacokinetics and pharmacodynamics, and maximum tolerated dose (MTD) of single ascending oral doses of RG7342, a positive allosteric modulator (PAM) of the metabotropic glutamate receptor 5 (mGlu5) for the treatment of schizophrenia, in healthy male subjects.
We find that reduced GluN2 phosphorylation can be precipitated by attenuated mGluR5 activity and that increased mGluR5 phosphorylation can result from decreased GluN function, suggesting a reciprocal interplay between the two pathways in schizophrenia.
These findings will inform translational approaches using this preclinical model and the pursuit of mGlu5 as therapeutic target for schizophrenia and other brain disorders.
These findings will inform translational approaches using this preclinical model and the pursuit of mGlu5 as therapeutic target for schizophrenia and other brain disorders.
Here, we summarise the known processes that regulate mGluR5 and those that have already been studied in schizophrenia, and discuss the consequences of this dysregulation for current mGluR5 pharmacological strategies.
The metabotropic glutamate receptor subtype 5 (mGlu5) is a closely associated signaling partner with NMDARs and regulates NMDAR function in forebrain regions implicated in the pathology of schizophrenia.
A comprehensive understanding of mGluR5 regulation in major depression, particularly in comparison to schizophrenia, is crucial as this has extensive implications for mGluR5 targeting novel therapeutics, especially considering that opposing modulation of mGluR5 is of therapeutic interest for these two disorders.
As a result, we identified one gene set with a joint effect significantly associated with schizophrenia and gene expression profiling analysis suggested that they were mainly neuro- and immune-related genes, such as glutamatergic gene (GRM5), GABAergic genes (GABRB1, GABARAP) and genes located in the MHC region (HLA-C, TAP2, HIST1H1B).
Previous work has suggested that activation of mGlu5 receptor augments NMDA receptor function and thereby may constitute a rational approach addressing glutamate hypofunction in schizophrenia and a target for novel antipsychotic drug development.
As a result, we identified one gene set with a joint effect significantly associated with schizophrenia and gene expression profiling analysis suggested that they were mainly neuro- and immune-related genes, such as glutamatergic gene (GRM5), GABAergic genes (GABRB1, GABARAP) and genes located in the MHC region (HLA-C, TAP2, HIST1H1B).
A comprehensive understanding of mGluR5 regulation in major depression, particularly in comparison to schizophrenia, is crucial as this has extensive implications for mGluR5 targeting novel therapeutics, especially considering that opposing modulation of mGluR5 is of therapeutic interest for these two disorders.
We observed multiple statistically significant mRNA and protein changes in levels of GABRθ, GABRρ2, mGluR5 and FMRP molecules including concordant reductions in mRNA and proteins for GABRθ and mGluR5 in lateral cerebella of subjects with schizophrenia; for increased mRNA and protein for GABRρ2 in lateral cerebella of subjects with bipolar disorder; and for reduced mRNA and protein for mGluR5 in BA9 of subjects with bipolar disorder.
To the best of our knowledge, this is the first evidence showing that the promoter methylation of the GMR2 and GMR5 genes greatly decreased the risk of schizophrenia, and the expression level of the GRM2, GRM5, and GRIA3 genes increased significantly in patients in comparison to healthy controls.
Selective activation of metabotropic glutamate receptor subtype 5 (mGlu5) may provide a novel therapeutic approach for treatment of symptoms associated with schizophrenia through facilitation of transmission through central glutamatergic circuits.
Furthermore, this review will discuss the potential of mGluR5 modulators in the therapy of schizophrenia as well as aspects of mGluR5 that require further characterisation.
The methylation of GRM2 and GRM5 greatly decreased the risk of schizophrenia in comparison to the reference unmethylated pattern [OR=0.38, 95% CI; 0.144-1.035, p=0.05; OR=0.06, 95% CI; 0.007-0.54.10, p=0.01], respectively.