Synthesis and evaluation of [11C]MMPIP as a potential radioligand for imaging of metabotropic glutamate 7 receptor in the brain

Neuroimaging genetics approaches to identify new biomarkers for the early diagnosis of autism spectrum disorder

Autism-spectrum disorders (ASDs) are developmental disabilities that manifest in early childhood and are characterized by qualitative abnormalities in social behaviors, communication skills, and restrictive or repetitive behaviors. To explore the neurobiological mechanisms in ASD, extensive research has been done to identify potential diagnostic biomarkers through a neuroimaging genetics approach. Neuroimaging genetics helps to identify ASD-risk genes that contribute to structural and functional variations in brain circuitry and validate biological changes by elucidating the mechanisms and pathways that confer genetic risk. Integrating artificial intelligence models with neuroimaging data lays the groundwork for accurate diagnosis and facilitates the identification of early diagnostic biomarkers for ASD. This review discusses the significance of neuroimaging genetics approaches to gaining a better understanding of the perturbed neurochemical system and molecular pathways in ASD and how these approaches can detect structural, functional, and metabolic changes and lead to the discovery of novel biomarkers for the early diagnosis of ASD.

The mGlu7 receptor in schizophrenia - An update and future perspectives

The mGlu₇ receptor belongs to the III group of metabotropic glutamatergic (mGlu) receptors and physiologically serves as an "emergency" receptor that is activated by high, almost pathological, glutamate concentrations. Of all mGlu receptors, this receptor is most highly expressed in the brain. Additionally, relatively intense expression of the receptor was found at the periphery, for example in the bowels or in the reproductive system of male mice, but this review will be focused predominantly on its role in the brain. In the CNS, the receptor is expressed presynaptically, in the center of the synaptic cleft, at the terminals of both excitatory glutamatergic and inhibitory GABAergic neurons. Thus, it may regulate the release of both glutamate and GABA. Schizophrenia is thought to develop as a consequence of a disturbed glutamatergic-GABAergic balance in different parts of the brain. Thus, the mGlu₇ receptor may be involved in the pathophysiology of schizophrenia and consequently constitute the target for antipsychotic drug discovery. In this review, we summarize the available data about mGlu₇ receptor ligands and their activity in animal models of schizophrenia. At present, only a few ligands are available, and negative allosteric modulators (NAMs) appear to exert antipsychotic-like efficacy, indicating that the inhibition of the receptor could constitute a promising target in the search for novel drugs. Additionally, the data concerning the expression of the receptor in the CNS and putative mechanisms by which its inhibition may contribute to the treatment of schizophrenia will be discussed. Finally, the polymorphisms of genes encoding the receptor in schizophrenic patients will also be provided.

Progress toward allosteric ligands of metabotropic glutamate 7 (mGlu7) receptor: 2008-present

Metabotropic glutamate type 7 (mGlu7) receptor is a member of the group III family of mGlu receptors. It is widely distributed in the central nervous system (CNS) and is preferentially expressed on presynaptic nerve terminals where it is thought to play a critical role in modulating normal neuronal function and synaptic transmission, making it particularly relevant in neuropharmacology. The lack of small-molecule mGlu7 ligands with adequate potency, selectivity and drug-like properties has resulted in difficulties in the preclinical validation of mGlu7 modulation in disease models. In the last decade, allosteric modulators of mGlu7 receptors have emerged as valuable tools with good potency, selectivity and physicochemical properties to study and unleash the therapeutic potential of mGlu7 receptors. This review focusses on the medicinal chemistry of mGlu7 receptor allosteric ligands discovered since 2008.

Practical Strategies and Concepts in GPCR Allosteric Modulator Discovery: Recent Advances with Metabotropic Glutamate Receptors

Allosteric modulation of GPCRs has initiated a new era of basic and translational discovery, filled with therapeutic promise yet fraught with caveats. Allosteric ligands stabilize unique conformations of the GPCR that afford fundamentally new receptors, capable of novel pharmacology, unprecedented subtype selectivity, and unique signal bias. This review provides a comprehensive overview of the basics of GPCR allosteric pharmacology, medicinal chemistry, drug metabolism, and validated approaches to address each of the major challenges and caveats. Then, the review narrows focus to highlight recent advances in the discovery of allosteric ligands for metabotropic glutamate receptor subtypes 1-5 and 7 (mGlu1-5,7) highlighting key concepts ("molecular switches", signal bias, heterodimers) and practical solutions to enable the development of tool compounds and clinical candidates. The review closes with a section on late-breaking new advances with allosteric ligands for other GPCRs and emerging data for endogenous allosteric modulators.