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Currently, there are no effective drugs for the treatment of amyotrophic lateral sclerosis (ALS). Only two drugs-edaravone and riluzole-have been approved, but they have very limited efficacy. The aim of this work was to modify the structural core of the Edaravone-phenylpyrazolone moiety and combine it with aminoadamantane pharmacophore in order to expand the spectrum of its action to a number of processes involved in the pathogenesis of ALS. New conjugates of edaravone derivatives with 1-aminoadamantanes combined with alkylene or hydroxypropylene spacers were synthesized, and their biological activity was investigated. Compounds were found that could inhibit lipid peroxidation and calcium-related mitochondrial permeability, block fast sodium currents of CNS neurons, and reduce aggregation of the mutated form of the FUS-protein typical to ALS. So, the proposed modification of the edaravone molecule has allowed the obtaining of new original structures that combine some prospective therapeutic mechanisms against key chains of the pathogenesis of ALS. The identified lead compounds can be used for further optimization and development of new promising drugs on this basis for the treatment of ALS.

An efficient regioselective approach to novel functionalized bis(isoxazoles) with a variety of aromatic and aliphatic linkers was elaborated, based on the heterocyclization reaction of electrophilic alkenes under the treatment with tetranitromethane-triethylamine complex affording 3-EWG-5-nitroisoxazoles. The subsequent S N Ar reactions of 5-nitroisoxazoles with various O , O -, N , N - and S , S -bis(nucleophiles) provide a wide range of bis(isoxazole) derivatives in good isolated yields. Employing an elaborated method, a series of novel bis(3-EWG-isoxazoles) as the promising allosteric modulators of AMPA receptors were designed and synthesized. The effect of the compounds on the kainate-induced currents was studied in the patch clamp experiments, revealing modulator properties for several of them. The best positive modulator potency was found for dimethyl 5,5'-(ethane-1,2-diylbis(sulfanediyl))bis(isoxazole-3-carboxylate), which potentiated the kainate-induced currents in a wide concentration range (10 -12 -10 -6 M) with maximum potentiation of 77% at 10 -10 M. The results were rationalized using molecular docking and molecular dynamics simulations of modulator complexes with the dimeric ligand-binding domain of the GluA2 AMPA receptor. The predicted physicochemical, ADMET, and PAINS properties confirmed that the AMPA receptor modulators based on the bis(isoxazole) scaffold may serve as potential lead compounds for the development of neuroprotective drugs.

Positive allosteric modulators (PAMs) of AMPA receptors represent attractive candidates for the development of drugs for the treatment of cognitive and neurodegenerative disorders. Dimeric molecules have been reported to have an especially potent modulating effect, due to the U-shaped form of the AMPA receptor's allosteric binding site. In the present work, novel bis(pyrimidines) were studied as AMPA receptor modulators. A convenient and flexible preparative approach to bis(pyrimidines) containing a hydroquinone linker was elaborated, and a series of derivatives with varied substituents was obtained. The compounds were examined in the patch clamp experiments for their influence on the kainate-induced currents, and 10 of them were found to have potentiating properties. The best potency was found for 2-methyl-4-(4-((2-methyl-5,6,7,8-tetrahydroquinazolin-4-yl)oxy)phenoxy)-6,7,8,9-tetrahydro-5 H -cyclohepta[ d ]pyrimidine, which potentiated the kainate-induced currents by up to 77% in all tested concentrations (10 -12 -10 -6 M). The results were rationalized via the modeling of modulator complexes with the dimeric ligand binding domain of the GluA2 AMPA receptor, using molecular docking and molecular dynamics simulation. The prediction of ADMET, physicochemical, and PAINS properties of the studied bis(pyrimidines) confirmed that PAMs of this type may act as the potential lead compounds for the development of neuroprotective drugs., Competing Interests: The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

A convenient synthetic approach to novel functionalized bis(isoxazoles), the promising bivalent ligands of the AMPA receptor, was elaborated. It was based on the heterocyclization reactions of readily available electrophilic alkenes with the tetranitromethane-triethylamine complex. The structural diversity of the synthesized compounds was demonstrated. In the electrophysiological experiments using the patch clamp technique on Purkinje neurons, the compound 1,4-phenylenedi(methylene)bis(5-aminoisoxazole-3-carboxylate) was shown to be highly potent positive modulator of the AMPA receptor, potentiating kainate-induced currents up to 70% at 10 -11 M.

A new series of conjugates of aminoadamantane and γ-carboline, which are basic scaffolds of the known neuroactive agents, memantine and dimebon (Latrepirdine) was synthesized and characterized. Conjugates act simultaneously on several biological structures and processes involved in the pathogenesis of Alzheimer's disease and some other neurodegenerative disorders. In particular, these compounds inhibit enzymes of the cholinesterase family, exhibiting higher inhibitory activity against butyrylcholinesterase (BChE), but having almost no effect on the activity of carboxylesterase (anti-target). The compounds serve as NMDA-subtype glutamate receptor ligands, show mitoprotective properties by preventing opening of the mitochondrial permeability transition (MPT) pore, and act as microtubule stabilizers, stimulating the polymerization of tubulin and microtubule-associated proteins. Structure-activity relationships were studied, with particular attention to the effect of the spacer on biological activity. The synthesized conjugates showed new properties compared to their prototypes (memantine and dimebon), including the ability to bind to the ifenprodil-binding site of the NMDA receptor and to occupy the peripheral anionic site of acetylcholinesterase (AChE), which indicates that these compounds can act as blockers of AChE-induced β-amyloid aggregation. These new attributes of the conjugates represent improvements to the pharmacological profiles of the separate components by conferring the potential to act as neuroprotectants and cognition enhancers with a multifunctional mode of action.

Using the patch-clamp method in the whole cell configuration, it was shown that external potassium ions play an important role in the regulation of calcium-activated chloride channels (CaCCs). A clear dependence of the conductivity of the СаССs on the external potassium concentration was shown. The effect of external potassium in the range 0-15 mM on the conductivity of chloride channels was significantly greater than the effect it had on other ionic currents (sodium or potassium). There is reason to believe that these changes in the conductivity of CaCCs may contribute to the development of pathophysiological processes such as hypokalemia or hyperkalemia., (© 2021. Pleiades Publishing, Ltd.)

Using the patch-clamp method in the whole cell configuration, it was shown that new conjugates of 2-aminothiophene-3-carboxylic acid with adamantane derivatives exhibit the ability to modulate CaCC activity in the single Purkinje neurons of rat cerebellum. It was noted that, depending on the nature of the substitution in the thiophene fragment, the nature of the effect on CaCC varies from inhibition to potentiation of CaCC currents. The described compounds are also blockers of the NMDA receptor ifenprodile site, which may have an additional neuroprotective contribution to the spectrum of biological activity of these compounds.

A new derivative of 3,7-diazabicyclo[3.3.1]nonane, which showed a high activity as a positive allosteric modulator of AMPA receptors of the CNS, was studied in electrophysiological experiments. At doses of 0.01 mg/kg, this compound significantly improved the memory of experimental animals disturbed by maximal electric shock. The results indicate that this compound is a promising candidate for preclinical trials and clinical studies as a drug for treatment of a number of psychoneurological diseases.

The first example of a novel class of AMPA receptor positive allosteric modulators of the bis(pyrimidine) series having a hydroquinone linker has been obtained and showed a potency to increase kainate-induced currents at subnanomolar concentrations., (This journal is © The Royal Society of Chemistry 2019.)

Using the patch-clamp method in the whole-cell configuration, we showed that the new derivatives of 2-aminothiophene-3-carboxylic acid, which were synthesized by us earlier, can both block (compound 1) and potentiate (compound 2) calcium-activated chloride currents in single rat cerebellar Purkinje cells.

A decrease in the external chloride ion concentration to 4 mM caused a decrease in the fast sodium current to 85-100% in rat cerebellum Purkinje neurons in the whole-cell configuration using the patchclamp method. This effect did not depend on the main cation from the internal side of the cell membrane (120 mM of potassium or cesium) and also appeared when Cl - was substituted with sulfate (SO 2 -4 ) or phosphate (H 2 PO 4 - ) anion outside of the cell. The effect was reversible after washing out the low chloride by the standard saline.

The whole-cell voltage clamp technique was employed to record the total ionic currents in rat cerebellar Purkinje neurons. When intrapipette solution contained 120 mM KCl, replacement of the standard external physiological saline with Na-free solution resulted in appearance of inward tail current after the end of the depolarizing pulse. When intrapipette potassium ions were replaced for cesium ones, the tail currents were observed even in the presence of normal Na + concentration (140 mM) in the external solution. Tail currents were not observed when external solution contained no Cl - and/or Ca 2+ ions. Niflumic acid (25-100 μM) blocked these currents by 80-100%. Complete replacement of external Na + for Tris ions pronouncedly augmented the amplitude and duration of the tail currents. These findings suggest that the tail transients in rat cerebellar Purkinje neurons are calcium-activated chloride currents whose amplitude and kinetics depend on ionic composition of the extracellular and intracellular solutions.

We have previously shown that neuropeptide cycloprolylglycine (CPG) increases the content of brain-derived neurotrophic factor (BDNF) in the culture of neuronal cells under normal conditions and in pathology. This is the first study to show that CPG at a physiological concentration of 10 -6 M significantly enhances the transmembrane AMPA currents in rat cerebellar Purkinje cells. Thus, CPG is a positive endogenous modulator of AMPA receptors. It was assumed that the neuropsychotropic effects of CPG are implemented as a result of BDNF accumulation after the activation of AMPA receptors by this neuropeptide.

Using patch-clamp method (whole cell configuration), it was shown that tetraethylammonium (TEA) and 4-aminopyridine (4-AP) block calcium-dependent chloride currents in the membrane of freshly isolated cerebellar Purkinje cells of rats (12-15 days). In the concentration range studied (50 μM-10 mM TEA and 100 μM-1 mM 4-AP), both compounds blocked the chloride current at IC 50 130 μM for TEA and 110 μM for 4-AP. TEA blockade was reversible after washing. The effect of 4-AP at concentrations greater than 100 μM was irreversible: both outward and inward chloride currents were blocked even after the removal of 4-AP from the incubation medium.

The presence of calcium-dependent potential-activated chloride currents in the membranes of freshly isolated rat cerebellar Purkinje cells (12-15 days) was shown by the whole-cell patch clamp technique. Chloride currents appeared in a sodium-free external solution and reversibly disappeared in the absence of external chloride and calcium ions.

We studied the effect of somatostatin on presinaptic NMDA receptors and postsinaptic GABA, NMDA, and AMPA receptors in rat brain. It was shown that somatostatin inhibits NMDA-induced (45)Ca(2+) uptake into synaptosomes isolated from rat brain cortex (IC50=2.8×10(-11) M). Somatostatin potentiates AMPA receptors and inhibits hippocampal NMDA receptors in the entire range of examined concentrations (10(-14)-10(-7) M); it also potentiates or inhibits GABA receptor currents in a concentration-dependent manner. Our results suggest that somatostatin modulates the function of ionotropic glutamate and GABA receptors and is involved in cognitive and neurodegenerative processes in the mammalian brain.

Using the patch-clamp technique the action of internal barium- and magnesium-ions on the calcium-dependent potassium channel in the membrane of vascular smooth muscle cells from the media layer of the human aorta was studied. Under symmetrical potassium conditions in excised inside-out patches bathed in the standard solution containing EGTA, the addition of barium as well as magnesium led to a concentration-dependent shift of the activation-curves to negative values of the membrane potential compared with the control, a block of single channel activity by barium, whereas no inhibitory effects by magnesium were registered. Thus, these results suggest that the process of channel activation of the calcium-dependent potassium channel of high conductance depends not merely on calcium but also on other divalent earthalkali ions.