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Background: N-methyl-D-aspartate receptors (NMDARs) are members of the ionotropic glutamate receptor family. These ligand-gated channels are entwined with numerous fundamental neurological functions within the central nervous system (CNS), and numerous neuropsychiatric disorders may arise from their malfunction. Methods: The purpose of the present review is to provide a detailed description of NMDARs by addressing their molecular structures, activation mechanisms, and physiological roles in the mammalian brain. In the second part, their role in various neuropsychiatric disorders including stroke, epilepsy, anti-NMDA encephalitis, Alzheimer's and Huntington's diseases, schizophrenia, depression, neuropathic pain, opioid-induced tolerance, and hyperalgesia will be covered. Results: Finally, through a careful exploration of the main non-competitive NMDARs antagonists (channel-blockers). Conclusion: We discuss the strengths and limitations of the various molecular structures developed for diagnostic or therapeutic purposes. [ABSTRACT FROM AUTHOR]

Purpose: NMDA receptors (NMDARs) dysfunction plays a central role in the physiopathology of psychiatric and neurodegenerative disorders whose mechanisms are still poorly understood. The development of a PET (positron emission tomography) tracer able to selectively bind to the NMDARs intra-channel PCP site may make it possible to visualize NMDARs in an open and active state. We describe the in vitro pharmacological characterization of [18F]-fluoroethylnormemantine ([18F]-FNM) and evaluate its ability to localize activated NMDA receptors in a rat preclinical model of excitotoxicity. Procedures: The affinity of the non-radioactive analog for the intra-channel PCP site was determined in a radioligand competition assay using [3H]TCP ([3H]N-(1-[thienyl]cyclohexyl)piperidine) on rat brain homogenates. Selectivity was also investigated by the displacement of specific radioligands targeting various cerebral receptors. In vivo brain lesions were performed using stereotaxic quinolinic acid (QA) injections in the left motor area (M1) of seven Sprague Dawley rats. Each rat was imaged with a microPET/CT camera, 40 min after receiving a dose of 30 MBq + / − 20 of [18F]-FNM, 24 and 72 h after injury. Nine non-injured rats were also imaged using the same protocol. Results: FNM displayed IC50 value of 13.0 ± 8.9 µM in rat forebrain homogenates but also showed significant bindings on opioid receptors. In the frontal and left somatosensory areas, [18F]FNM PET detected a mean of 37% and 41% increase in [18F]FNM uptake (p < 0,0001) 24 and 72 h after QA stereotaxic injection, respectively, compared to the control group. Conclusions: In spite of FNM's poor affinity for NMDAR PCP site, this study supports the ability of this tracer to track massive activation of NMDARs in neurological diseases. [ABSTRACT FROM AUTHOR]

Abstract: This study presents the binding and functional properties of the mouse NPFF2 (mNPFF2) receptor, in comparison with its human counterpart (hNPFF2). Binding experiments were performed by using the NPFF2 selective radioligand [3H]-EYF in membranes from CHO cells transfected with mouse and human NPFF2 receptors and compared to membranes from mouse olfactory bulb, the brain region expressing the highest density of NPFF2 receptors in mouse. mNPFF2 receptors exhibited a high affinity (Kd=0.2–0.4nM) for [3H]-EYF, comparable to that of hNPFF2 receptors. Also, the binding selectivity profile of mNPFF2 receptors was comparable to that of hNPFF2 receptors, except for three ligands (NPSF, NPVF, RF9) that were about tenfold more potent and active on mouse receptors than on human receptors. In particular, compared to hNPFF2 receptors, mNPFF2 receptors were less discriminative towards the proNPFFB-derived peptide. This suggests some species-related differences in the binding properties of NPFF2 receptors that could have repercussion when evaluating the pharmacological properties of drugs in vivo. [Copyright &y& Elsevier]

Abstract: The binding characteristics of [3H]-NPVF and [3H]-EYF, the two first tritiated probes for the respective labelling of NPFF1 and NPFF2 receptors, are presented. In membranes from CHO cells transfected with the human NPFF1 receptor, [3H]-NPVF labelled one class of binding sites with a high affinity (Bmax=4pmol/mg protein, Kd=2.65nM). In membranes from CHO cells transfected with the human NPFF2 receptor, [3H]-EYF labelled one class of binding sites with a high affinity (Bmax=16pmol/mg protein, Kd=0.54nM). Both radioligands exhibited time-dependent binding, low (10–20%) non-specific binding and poor cross-reactivity towards the related receptor subtype. The potency of different NPFF ligands to displace [3H]-NPVF and [3H]-EYF binding profiles was in good agreement with the profile previously measured by using 125I-probes (NPFF1 receptor: NPVF≥1DMe=SPA-NPFF>NPFF=SQA-NPFF=QFW-NPSF>NPSF>RF9; NPFF2 receptor: SPA-NPFF>>SQA-NPFF=QFW-NPSF=1DMe=NPFF≫NPSF=NPVF>RF9). Therefore, [3H]-NPVF and [3H]-EYF are new valuable tools for performing binding on NPFF receptors. [Copyright &y& Elsevier]

Multiple sclerosis (MS) is a disease of the central nervous system with a very debilitating inflammatory component that usually affects young people (years 20-40). This disease is characterized by the progressive destruction of the myelin sheath of the axons by the cells of the immune system, which results in neuronal degeneration. The T and B lymphocytes are the main players in this disease, which can be remittent with relapses or progressive. Among the drugs used to treat MS is the immunosuppressor fingolimod, the targets of which are the sphingosine 1-phosphate receptors. This molecule acts orally by preventing lymphocytes from leaving the thymus and lymph nodes and from reaching inflammatory brain foci. Other immunosuppressive drugs affecting sphingosine 1-phosphate receptors are under development and an intense search for curative drugs and treatments is being conducted., (© 2020 médecine/sciences – Inserm.)

The expression of the EGFP-human mu-opioid receptor fusion protein in the methylotrophic yeast Pichia pastoris was optimized and monitored using both fluorescence and ligand-binding experiments. A set of parameters, including gene copy number, strain type, temperature, pH, and methanol inducer levels, was studied for its effect on the production of the recombinant protein. We show here that the expression level is optimal after 10 h of promoter induction and that the maximum is reached at a lower temperature and a higher pH than normally used. The optimized conditions have allowed a fourfold increase of the ligand-binding active form of the receptor, whereas the total expression level determined by EGFP fluorescence measurements was not modified., (Copyright 2002 Elsevier Science (USA).)