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Cervical spinal cord injury (SCI) is a traumatic condition where individuals lose crucial motor and sensory functions in their hands and arms. These deficits can be caused by myelin damage, which exposes juxtaparanodal potassium channels leading to large potassium effluxes and ultimately, shortened and decreased conduction. However, potassium channel blockers such as 4-aminopyridine (4-AP) and the novel derivative, 4-aminopyridine-3-methanol (4-AP-3-MeOH) prevent potassium ion leakage and increase conduction to improve motor function. Currently, it is possible to regain voluntary motor control and strength in the forelimbs and hands by using complementary electrical stimulation, pharmacological agents and training to transform dormant spinal circuitry into active states. Here, we evaluated the extent to which potassium channel blockers, 4-AP and 4-AP-3-MeOH enable functional forelimb ability when used in combination with spinal stimulation and motor training after incomplete cervical SCI. 4-AP restored reaching and grasping function and muscle activation in rats after two weeks of treatment. 4-AP-3-MeOH, however, did not lead to improve motor functioning or muscle activation. Both drugs decreased muscle activation latency and allowed for earlier muscle activation. Our findings suggest 4-AP synergistically works with spinal stimulation and training to enable spared circuitry following SCI and can be used acutely to restore forelimb function.

The objective of the present study was to scrutinize the effect of nitric oxide (NO), cyclic GMP (cGMP), potassium channel blockers, and metformin on the citral-produced peripheral antinociception. The rat paw 1% formalin test was used to assess nociception and antinociception. Rats were treated with local peripheral administration of citral (10–100 µg/paw). The antinociception of citral (100 µg/paw) was evaluated with and without the local pretreatment of naloxone, NG-L-nitro-arginine methyl ester (L-NAME, a NO synthesis inhibitor), 1H-(1,2,4)-oxadiazolo(4,2-a)quinoxalin-1-one (ODQ, a soluble guanylyl cyclase inhibitor), metformin, opioid receptors antagonists, and K+ channel blockers. Injection of citral in the rat paw significantly decreased the nociceptive effect of formalin administration during the two phases of the test. Local pretreatment of the paws with L-NAME and ODQ did not reduced the citral-induced antinociception. Glipizide or glibenclamide (Kir6.1-2; ATP-sensitive K+ channel blockers), tetraethylammonium or 4-aminopyridine (KV; voltage-gated K+ channel blockers), charybdotoxin (KCa1.1; big conductance calcium-activated K+ channel blocker), apamin (KCa2.1-3; small conductance Ca2+-activated K+ channel antagonist), or metformin, but not the opioid antagonists, reduced the antinociception of citral. Citral produced peripheral antinociception during both phases of the formalin test. These effects were due to the activation of K+ channels and a biguanide-dependent mechanism.

Pellino-2 is an E3 ubiquitin ligase that mediates intracellular signaling in innate immune pathways. Most studies of endogenous Pellino-2 have been performed in macrophages, but none in nonimmune cells. Using yeast two-hybrid screening and co-immunoprecipitation, we identified six novel interaction partners of Pellino-2, with various localizations: insulin receptor substrate 1, NIMA-related kinase 9, tumor necrosis factor receptor-associated factor 7, cyclin-F, roundabout homolog 1, and disheveled homolog 2. Pellino-2 showed cytoplasmic localization in a wide range of nonimmune cells under physiological potassium concentrations. Treatment with the potassium ionophore nigericin resulted in nuclear localization of Pellino-2, which was reversed by the potassium channel blocker tetraethylammonium. Live-cell imaging revealed intracellular migration of GFP-tagged Pellino-2. In summary, Pellino-2 interacts with proteins at different cellular locations, taking part in dynamic processes that change its intracellular localization influenced by potassium efflux. publishedVersion

The effects of 5/6 nephrectomy on contractile and dilatory properties of the superior mesenteric artery (SMA) and internal carotid artery (ICA) segments in spontaneously hypertensive rats (SHR) were studied under isometric conditions by wire myography. Subtotal 5/6 nephrectomy (5/6 Nx) in 3-month-old rats was taken as a chronic kidney disease model. Dilatation of phenylephrine-preconstricted arterial segments was elicited by acetylcholine (AСh) or sodium nitroprusside (SNP) in the absence and presence of potassium channel blockers (tetraethylammonium, glibenclamide) or a guanylyl cyclase inhibitor methylene blue. In 5/6 Nx vs. control rats, the phenylephrine-induced contractile response of the SMA was only slightly reduced, but significantly reduced in the presence of methylene blue. In the ICA of 5/6 Nx vs. control rats, this response was significantly weaker both in the absence and presence of the potassium channel blockers and guanylyl cyclase inhibitor. 5/6 nephrectomy had no effect on the dilatory response of both arteries to AСh or SNP, however, the contractile phase of the ICA response to AСh in the presence of glibenclamide significantly decreased in 5/6 Nx, but not in control, rats. It is concluded that chronic kidney disease may attenuate endothelium-dependent and independent vasoconstriction in SHR, to a greater extent in the ICA than SMA, as well as differently affect the signaling pathways of these responses in different types of arteries, involving ATP-sensitive potassium channels in the ICA and guanylyl cyclase in the SMA.

Background and purpose KV 1.3 potassium channels play a predominant role in regulating calcium signalling that is essential for the activation and proliferation of effector memory T (TEM ) cells. This ion channel has been recognized as a promising therapeutic target against various autoimmune diseases. Experimental approach In a high-throughput screening programme, WP1066 was identified as a KV 1.3 channel inhibitor. Using molecular biology and electrophysiological methods, the mechanism(s) underlying WP1066 blockade of Kv1.3 channels was investigated. Using TEM cell proliferation assay and mouse delayed-type hypersensitivity (DTH) model, the effects of WP1066 were examined. Key results WP1066 blocked KV 1.3 channels in a dose-dependent manner with an IC50 of 3.2 μM and induced a hyperpolarizing shift of the steady-state inactivation curve. This blockade was use-dependent, as WP1066 interacted preferentially with channels in their open state, rather than the closed state or inactivated state. When the residues located in the S6 domain scaffolding the inner vestibule, were sequentially mutated, the potency of WP1066 was significantly impaired, especially by mutations A413C and I420C, indicating a higher affinity of interacting sites for WP1066. Moreover, WP1066 effectively suppressed mouse TEM cell proliferation in vitro and mouse DTH reaction in vivo. Conclusions and implications The results presented here have identified WP1066 as a KV 1.3 channel blocker with an open-state-dependent property, providing fundamental evidence for the application of WP1066 in further immunomodulatory studies targeting KV 1.3 channels.

Background In the current study, a simple, improved, precise, rapid, and accurate reverse phase liquid chromatographic method was produced for the estimation of dalfampridine in bulk and tablet dosage form which is a potassium channel blocker used for the treatment of multiple sclerosis (MS). The separation of dalfampridine was achieved isocratically on a C18 column (250 × 4.6 mm, 5 μm) using (0.1% v/v) buffer pH 3.0 ± 0.05 adjusted with diluted orthophosphoric acid (OPA) and acetonitrile (ACN) in the ratio of 60:40% (v/v) as a mobile phase, at a flow rate of 0.5 mL/min, and column temperature of 40 °C. HPLC grade methanol as diluents was used. Five microliters of the standard solution of the drug was injected, and the eluted analytes were detected at 262 nm. Results Dalfampridine was eluted at 4.5 min with a run time of 10 min. Linearity in the method was measured in the concentration range of 25–75 ppm with a correlation coefficient of 0.999. Limit of detection and limit of quantitation were found to be 0.711 μg/mL and 2.154 μg/mL, respectively. Dalfampridine was subjected for forced degradation stability study in conditions of thermal, acid, alkali, and oxidation and photo-degradation condition. The degradants were well resolved from the dalfampridine main peak. Validation of the developed method is carried as per USFDA and ICH guidelines. Conclusion The results of the analysis prove that the method is simple, improved, precise, accurate, and rapid for estimating the content of dalfampridine in bulk drug and tablet dosage form and can be applied for routine analysis.

In this work, a stochastic Langevin approach is adopted to coupled Hodgkin-Huxley neuron system to elucidate the role of channel noise in the kinetics and energetics of spiking of action potential and the synchronization between neurons. The size of patch plays a pivotal role in synchronization and metabolic energy consumption. The behavior of postsynaptic neuron is explored by taking three different patch size ranges from noise enhanced phase to dead range state before reaching a deterministic limit. We also discuss the effect of sodium and potassium channel blockers on kinetic and energetic characteristics of synchronization and metabolic energy consumption rate.

A high salt diet leads to a decrease in vascular dilatation to agonists, but the vascular mechanisms involved in this process are not extensively studied. A group of male Wistar rats at the age of 3 months was transferred to a high-salt diet containing 8% NaCl (HS) for 3 months, while the second group received a normal-salt diet with a standard salt content (0.34%) (NS). At the end of the experiment, the rats were euthanized and the abdominal aorta and superior mesenteric artery (SMA) were extracted. The vascular segments were placed into a myograph, and the acetylcholine (ACh)-induced relaxation of the phenylephrine (PHE)-precontracted vascular segments was measured. A high-salt diet led to attenuate the relaxation of the SMA in a calcium-free solution. In response to ACh and sodium nitroprusside, a pronounced relaxation of the vascular segments was observed, while the ACh-induced vascular relaxation in HS rats showed a lower amplitude. Potassium channel blockers (TEA, TRAM-34, apamine) attenuated the ACh-induced relaxation of the SMA, but not the aorta. In the SMA of HS rats, a decrease in the relaxation under the effect of K+ channel blockers was more prominent. Inhibition of the production of endogenous hydrogen sulfide (H2S) also led to attenuate the ACh-induced relaxation of SMA segments. In SMA of HS rats, the degree of attenuation of the ACh-induced relaxation against the background of propargylglycine was larger than in NS rats. The data obtained in the study show that a long-term high-salt diet leads to a decrease in agonist-induced relaxation of the aortic segments and SMA due to a decrease in the production of NO by the endothelium. In the SMA of HS rats, a decrease in NO-mediated relaxation is partially compensated by the increasing role of EDHF in ACh-induced relaxation. The results of the study also show that one of the EDHFs in the rat SMA is H2S, the role of which in SMA relaxation increases in HS rats.

4-Aminopyridine (4-AP) is a potassium channel blocker that enhances nerve excitability. In this study, rat models that have facial nerve crush injury (FNCI) were grouped and treated with methylprednisolone (MP), 4-AP, and a combination of these two drugs. Electrophysiologic and histopathologic outcomes of these groups will be compared with a control group. Thirty healthy male Wistar rats (mean weight of 265 g) were used in this study. The rats were randomly divided into five groups with six subjects in each: Group 1 (sham group), Group 2 (control group), Group 3 (MP group), Group 4 (4-aminopyridine group), and Group 5 (4-AP + MP group). All groups except the sham group underwent crush injury to the right facial nerve. Electrophysiologic and histologic recovery was recorded three weeks postoperatively. The 4-AP group and the combined group had a more significant recovery at Nerve Excitability Thresholds (NET) at the end of three weeks. The methylprednisolone group and the control group had a minimal recovery of NET. Histologically, when compared with the control group, the combined group was the only group that had significant recovery at all three of axonal degeneration, axon diameter, and myelin thickness. In this experimental study, we demonstrated that a combination treatment of 4-AP and MP is more effective in the recovery of peripheric FNCI than in the no-treatment control group and in the 4-AP- or MP-alone groups. Moreover, our results suggested that 4-AP can be a potent alternative to MP in the treatment of the FNCI. N/A.

Root ofChrysopogon zizanioides(L.) Roberty has been used in Siddha system of medicine to treat hypertension. The present study was therefore to investigate the vasorelaxation effect of root essential oil ofC. zizanioidesusing rat isolated thoracic aortic rings. Chemical characterization of root essential oil was carried out using Gas Chromatography–Flame Ionization Detector (GC–FID) and Gas Chromatography–Mass Spectrometry (GC–MS). Essential oil nanoemulsion (EONE) was prepared and characterized. Vasorelaxant effect of EONE in endothelium-intact aortic rings precontracted with phenylephrine (PE) (1 µM) or KCl (80 mM) was investigated. Role of Ca2+, nitric oxide and K+channels in precontracted aortic rings were investigated to elucidate the mechanism of action of the essential oil. Further, the role of muscarinic and prostacyclin receptors in EONE induced relaxation was studied. The EONE significantly induced relaxation (Emax77.1 ± 4.87%) in PE precontracted aortic rings. The nitric oxide synthase, and cyclooxygenase inhibitors and potassium channel blockers have not significantly inhibited the vasorelaxation induced by EONE. However, EONE induced relaxation in precontracted endothelium-intact aortic rings was significantly inhibited by muscarinic receptor and calcium channel. The root essential oil ofC. zizanioidespossesses vasorelaxant effect through muscarinic pathway as well as acts as calcium channel blocker.

Clinical and genetic features of five unrelated patients with de novo pathogenic variants in the synaptic vesicle-associated membrane protein 2 (VAMP2) reveal common features of global developmental delay, autistic tendencies, behavioral disturbances, and a higher propensity to develop epilepsy. For one patient, a cognitively impaired adolescent with a de novo stop-gain VAMP2 mutation, we tested a potential treatment strategy, enhancing neurotransmission by prolonging action potentials with the aminopyridine family of potassium channel blockers, 4-aminopyridine and 3,4-diaminopyridine, in vitro and in vivo. Synaptic vesicle recycling and neurotransmission were assayed in neurons expressing three VAMP2 variants by live-cell imaging and electrophysiology. In cellular models, two variants decrease both the rate of exocytosis and the number of synaptic vesicles released from the recycling pool, compared with wild-type. Aminopyridine treatment increases the rate and extent of exocytosis and total synaptic charge transfer and desynchronizes GABA release. The clinical response of the patient to 2 years of off-label aminopyridine treatment includes improved emotional and behavioral regulation by parental report, and objective improvement in standardized cognitive measures. Aminopyridine treatment may extend to patients with pathogenic variants in VAMP2 and other genes influencing presynaptic function or GABAergic tone, and tested in vitro before treatment.

By responding to environmental and intracellular stimuli, ion channels play critical roles in sperm function regulation. Although the importance of ion channel in male reproduction has drawn increasing attention in many species, the knowledge about ion channels in zebrafish sperm is limited. Here, we show zebrafish sperm motility could be suppressed by general calcium channel blockers rather than by general potassium channel blockers. Further investigation found that sperm motility was not only suppressed by antagonist for the transient receptor potential vanilloid channel, subtype 1 (Trpv1), but also restored by its agonist, suggesting functional presence of Trpv1 in zebrafish spermatozoa. As a consequence, the suppression of sperm motility by Trpv1 antagonist could reduce in vitro fertilization rate. Western blot and immunofluorescence analysis proved that Trpv1 was mainly distributed in the neck and tail regions of zebrafish sperm. Additionally, neither antagonist nor agonist of Trpv1 exhibited effect on the motility of trpv1−/− zebrafish sperm. To our knowledge, this is one of the limited studies showing the importance of ion channels in regulating zebrafish sperm function, and may enrich our understanding on male reproductive physiology of zebrafish and offer novel regulatory target for fish breeding and sperm cryopreservation.

In this study, we investigated the relaxation effect and mechanisms of patchouli alcohol (PA) on rat corpus cavernosum. Corpus cavernosum strips were used in organ baths for isometric tension studies. The results showed that PA demonstrated concentration-dependent relaxation effect on rat corpus cavernosum. The relaxant response to PA was not influenced by tetrodotoxin and atropine while it was significantly inhibited by removal of endothelium. L-NG-nitroarginine methyl ester (L-NAME, a nitric oxide synthase inhibitor) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor) significantly inhibited relaxation response to PA, whereas indomethacin (COX inhibitor) had no effect on PA-induced relaxation. The treatment of endothelium-deprived corpus cavernosum with several potassium channel blockers including tetraethylammonium (TEA), 4-aminopyridine (4-AP), and glibenclamide had no effect on PA-induced relaxation. Endothelium-deprived corpus cavernosal contractions induced by cumulative addition of Ca2+ to high KCl solution without CaCl2 were significantly inhibited by PA. Also, PA improved relaxant capacity of sildenafil in rat corpus cavernosum. In addition, the perfusion with PA significantly increased the levels of cGMP and expression of mRNA and protein of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS). Furthermore, intracavernous injection of PA enhanced the rise in intracavernous pressure in rats during cavernosal nerve electric stimulation. In conclusion, PA relaxed the rat corpus cavernosum attributed to both endothelium-dependent and -independent properties. While the former component was mostly involved in nitric oxide signaling pathway, the endothelium-independent mechanism involved in PA-induced relaxation was probably linked to calcium antagonism.

Resveratrol is found in numerous plant-based foods and beverages and is known to have an impact on the cardiovascular system. The aim of this study was to investigate the vasorelaxant effect of resveratrol and its underlying mechanisms by employing an aortic ring assay model. Resveratrol caused relaxation of aortic rings that had been precontracted with phenylephrine in the presence of endothelium or with potassium chloride in endothelium-intact aortic rings. The vasorelaxant effect was decreased in the absence of an endothelium. The mechanisms underlying the vasorelaxant effect of resveratrol were determined through the addition of antagonists. In the presence of the endothelium, indomethacin (a nonselective cyclooxygenase inhibitor), methylene blue (cyclic guanosine monophosphate lowering agent), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, selective soluble guanylate cyclase inhibitor), Nω-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), tetraethylammonium (TEA, nonselective calcium activator potassium channel blocker), 4-aminopyridine (4-AP, voltage-dependent K+ channel blocker), barium chloride (BaCl2, inwardly rectifying K+ channel blocker), glibenclamide (non-specific ATP-sensitive K+ channel blocker) and propranolol (β-adrenergic receptor blocker) led to a significant reduction in the vasorelaxation effect induced by resveratrol. Resveratrol was also found to reduce Ca2+ release from the sarcoplasmic reticulum and block calcium channels. In conclusion, resveratrol targets multiple signalling pathways for exerting its vasorelaxant effects in the rat aortic ring model in both the presence and absence of endothelium.

Tk-hefu is an artificial peptide designed based on the α-hairpinin scaffold, which selectively blocks voltage-gated potassium channels K(v)1.3. Here we present its spatial structure resolved by NMR spectroscopy and analyze its interaction with channels using computer modeling. We apply protein surface topography to suggest mutations and increase Tk-hefu affinity to the K(v)1.3 channel isoform. We redesign the functional surface of Tk-hefu to better match the respective surface of the channel pore vestibule. The resulting peptide Tk-hefu-2 retains K(v)1.3 selectivity and displays ∼15 times greater activity compared with Tk-hefu. We verify the mode of Tk-hefu-2 binding to the channel outer vestibule experimentally by site-directed mutagenesis. We argue that scaffold engineering aided by protein surface topography represents a reliable tool for design and optimization of specific ion channel ligands.

The discovery of ways to enhance skin healing is of great importance due to the frequency and severity of skin wounds. We discovered that 4-aminopyridine (4-AP), a potassium channel blocker, greatly enhances skin wound healing. Benefits include faster wound closure, restoration of normal-appearing skin architecture and epidermal thickness, increased vascularization and increases in K14+ keratinocytes. Hair follicle number was increased, both histologically and by analysis of K15 and K17 expression. Levels of vimentin (which marks fibroblasts) and α-smooth muscle actin (α-SMA, which marks collagen-producing myofibroblasts) increased, as did α-SMA+ cell numbers. 4-AP also increased numbers of axons and S-100+ Schwann cells, and increased expression of p75-NTR and SOX10. Treatment also increased levels of nerve growth factor, transforming growth factor-β, Substance P and PGP9.5, important modulators of wound healing. As 4-AP is already used for treatment of multiple sclerosis and other chronic neurological syndromes, it has strong potential for rapid translational development.

Pharmacology graduates require an understanding of both in vitro and in vivo drug responses but there has been a decline in animal use in pharmacology education over the last 30 years. To address this, we present the novel invertebrate model, Lumbriculus variegatus, for in vivo testing of drugs in a teaching environment. We have developed two novel behavioral assays: the stereotypical movement assay, which measures the effect of drugs on the ability of L. variegatus to perform stereotypical movements following tactile stimulation, and the free locomotion assay, which measures drug effects on unstimulated movement. We report the effects of compounds with diverse pharmacodynamic properties on L. variegatus using these assays. The ryanodine receptor antagonist, dantrolene, altered the unstimulated movement of L. variegatus at 5 μM, whereas stimulated movement was inhibited at ≥25 μM. Lidocaine, a voltage‐gated sodium channel blocker, and quinine, a nonselective sodium and potassium channel blocker, reduced both stimulated and unstimulated L. variegatus movement at ≥0.5 mM. Inhibitory effects of quinine persisted for up to 24 h after drug removal, whereas lidocaine effects were reduced 10 min after drug removal. Herein, we provide proof‐of‐concept utilization of L. variegatus as an organism for use in in vivo pharmacology education but without regulatory constraints or the need for specialized equipment and training., Lumbriculus variegatus were used as a novel organism for studying the effects of drug compounds on stereotypical behaviors and unstimulated movement for use within in vivo pharmacology education.

Thermal signals are critical elements in the operation of interoceptive and exteroceptive neural circuits, essential for triggering thermally-driven reflexes and conscious behaviors. A fraction of cutaneous and visceral sensory endings are activated by cold temperatures. Compared to somatic (DRG and TG) neurons, little is known about the mechanisms underlying cold sensitivity of visceral vagal neurons. We used pharmacological and genetic tools for a side-by-side characterization of cold-sensitive (CS) neurons in adult mouse trigeminal (TG) and vagal ganglia (VG).We found that CS neurons are more abundant in VG than in TG. In both ganglia, sensitivity to cold varied widely and was enhanced by the potassium channel blocker 4-AP. The majority of CS neurons in VG co-express TRPA1 markers and cold-evoked responses are severely blunted in Trpa1 KO mice, with little impact of TRPM8 deletion or pharmacological TRPM8 blockade. Consistent with these findings, the expression of TRPM8-positive neurons was low in VG and restricted to the rostral jugular ganglion. In vivo retrograde labelling of airway-innervating vagal neurons demonstrated their enhanced cold sensitivity and a higher expression of TRPA1 compared to neurons innervating the stomach wall. In contrast, the majority of CS TG neurons co-express TRPM8 markers and their cold sensitivity is reduced after TRPM8 deletion or blockade. However, pharmacological or genetic reduction of TRPA1 showed that these channels contribute significantly to their cold sensitivity in TG. In both ganglia, a fraction of CS neuron respond to cooling by a mechanism independent of TRPA1 or TRPM8 yet to be characterized.

Ketamine is a clinical anesthetic and antidepressant. Although ketamine is a known NMDA receptor antagonist, the mechanisms contributing to antidepression are unclear. This present study examined the loci and duration of ketamine’s actions, and the involvement of NMDA receptors. Local field potentials were recorded from the CA1 region of mouse hippocampal slices. Ketamine was tested at antidepressant and anesthetic concentrations. Effects of NMDA receptor antagonists APV and MK-801, GABA receptor antagonist bicuculline, and a potassium channel blocker TEA were also studied. Ketamine decreased population spike amplitudes during application, but a long-lasting increase in amplitudes was seen during washout. Bicuculline reversed the acute effects of ketamine, but the washout increase was not altered. This long-term increase was statistically significant, sustained for &gt, 2 h, and involved postsynaptic mechanisms. A similar effect was produced by MK-801, but was only partially evident with APV, demonstrating the importance of the NMDA receptor ion channel block. TEA also produced a lasting excitability increase, indicating a possible involvement of potassium channel block. This is this first report of a long-lasting increase in excitability following ketamine exposure. These results support a growing literature that increased GABA inhibition contributes to ketamine anesthesia, while increased excitatory transmission contributes to its antidepressant effects.

Introduction Drug-induced block of the hERG potassium channel could predispose to torsade de pointes, depending on occurrence of concomitant blocks of the calcium and/or sodium channels. Since the hERG potassium channel block affects cardiac repolarization, the aim of this study was to propose a new reliable index for non-invasive assessment of drug-induced hERG potassium channel block based on electrocardiographic T-wave features. Methods ERD30% (early repolarization duration) and TS/A (down-going T-wave slope to T-wave amplitude ratio) features were measured in 22 healthy subjects who received, in different days, doses of dofetilide, ranolazine, verapamil and quinidine (all being hERG potassium channel blockers and the latter three being also blockers of calcium and/or sodium channels) while undergoing continuous electrocardiographic acquisition from which ERD30% and TS/A were evaluated in fifteen time points during the 24 h following drug administration ("ECG Effects of Ranolazine, Dofetilide, Verapamil, and Quinidine in Healthy Subjects" database by Physionet). A total of 1320 pairs of ERD30% and TS/A measurements, divided in training (50%) and testing (50%) datasets, were obtained. Drug-induced hERG potassium channel block was modelled by the regression equation BECG(%) = a·ERD30% + b·TS/A+ c·ERD30%·TS/A + d; BECG(%) values were compared to plasma-based measurements, BREF(%). Results Regression coefficients values, obtained on the training dataset, were: a = -561.0 s-1, b = -9.7 s, c = 77.2 and d = 138.9. In the testing dataset, correlation coefficient between BECG(%) and BREF(%) was 0.67 (p Conclusion BECG(%) is a reliable non-invasive index for the assessment of drug-induced hERG potassium channel block, independently from concomitant blocks of other ions.

Exaggerated vasoconstriction plays a critical role in the development of hypertension in metabolic syndrome (MetS). A crude methanolic extract of Euryops arabicus (EA) was found to alleviate MetS-associated exaggerated vasoconstriction. The methanolic extract of EA had a direct vasodilatory effect which might account for the alleviation of vasoconstriction. Bio-guided fractionation revealed that the chloroform fraction is responsible for this effect. The observed vasodilation was not affected by Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), a nitric oxide (NO) synthase inhibitor or methylene blue (MB), a guanylate cyclase inhibitor, while it was increased by tetraethylammonium (TEA), a potassium channel blocker. In addition, the chloroform extract showed concentration-dependent inhibition of calcium-induced contraction. Chemical investigations of the chloroform fraction of EA revealed three new furanoeremophilanes, namely, 6-β-(2`-methyl-2`,3`-epoxy-propionyloxy)-10-α-H-9-oxofuranoeremophilane (4), 6- α -(2`-methyl, 2`,3`-epoxy-butyryloxy)-10-α-H-9-oxofuranoeremophilane (7), and 6-β-(2`-methyl, 2`,3`-epoxy-butyryloxy)-euryopsin (8), in addition to five other known metabolites, namely, 6-isovaleryloxy-euryopsin (1), 6-isopropionyl-euryopsin (adenostylone) (2), 6-senecioyl-euryopsin-9-one (3) 6-β -(2`-methyl-2`,3`-epoxy-butyryloxy)-10-α-H-9-oxofuranoeremophilane (5), and euryopsonol-senecioate (6). All the isolated compounds showed significant vasodilatory effects that might involve calcium channel blocking, and compounds 7 and 8 were found to be the most bioactive ones.

Introduction We recently demonstrated the beneficial effects of 4-aminopyridine (4-AP), a potassium channel blocker, in enhancing remyelination and recovery of nerve conduction velocity and motor function after sciatic nerve crush injury in mice. Although muscle atrophy occurs very rapidly after nerve injury, the effect of 4-AP on muscle atrophy and intrinsic muscle contractile function is largely unknown. Methods Mice were assigned to sciatic nerve crush injury and no-injury groups and were followed for 3, 7, and 14 days with/without 4-AP or saline treatment. Morphological, functional, and transcriptional properties of skeletal muscle were assessed. Results In addition to improving in vivo function, 4-AP significantly reduced muscle atrophy with increased muscle fiber diameter and contractile force. Reduced muscle atrophy was associated with attenuated expression of atrophy-related genes and increased expression of proliferating stem cells. Discussion These findings provide new insights into the potential therapeutic benefits of 4-AP against nerve injury-induced muscle atrophy and dysfunction. Muscle Nerve 60: 192-201, 2019.

Atrial fibrillation (AF) is a major cause of stroke, heart failure, sudden death and cardiovascular morbidity. The Kv1.5 potassium channel conducts the IKur current and has been demonstrated to be predominantly expressed in atrial versus ventricular tissue. Blockade of Kv1.5 has been proven to be an effective approach to restoring and maintaining sinus rhythm in preclinical models of AF. In the clinical setting, however, the therapeutic value of this approach remains an open question. Herein, we present synthesis and optimization of a novel series of 1,2-bis(aryl)ethane-1,2-diamines with selectivity for Kv1.5 over other potassium ion channels. The effective refractory period in the right atrium (RAERP) in a rabbit PD model was investigated for a selection of potent and selective compounds with balanced DMPK properties. The most advanced compound (10) showed nanomolar potency in blocking Kv1.5 in human atrial myocytes and based on the PD data, the estimated dose to man is 700 mg/day. As previously reported, 10 efficiently converted AF to sinus rhythm in a dog disease model.

BACKGROUND/AIMS:The phenylalkylamine class of L-type Ca2+ channel antagonist verapamil prolongs the effective refractory period (ERP) of human atrium, which appears to contribute to the efficacy of verapamil in preventing reentrant-based atrial arrhythmias including atrial fibrillation. This study was designed to investigate the molecular and electrophysiological mechanism underlying the action of verapamil on human Kv1.5 (hKv1.5) channel that determines action potential duration and ERP in human atrium., METHODS:Site-directed mutagenesis created 10 single-point mutations within pore region of hKv1.5 channel. Wholecell patch-clamp method investigated the effect of verapamil on wild-type and mutant hKv1.5 channels heterologously expressed in Chinese hamster ovary cells. Docking simulation was conducted using open-state homology model of hKv1.5 channel pore., RESULTS:Verapamil preferentially blocked hKv1.5 channel in its open state with IC50 of 2.4±0.6 μM (n = 6). The blocking effect of verapamil was significantly attenuated in T479A, T480A, I502A, V505A, I508A, L510A, V512A and V516A mutants, compared with wild-type hKv1.5 channel. Computer docking simulation predicted that verapamil is positioned within central cavity of channel pore and has contact with Thr479, Thr480, Val505, Ile508, Ala509, Val512, Pro513 and Val516., CONCLUSION:Verapamil acts as an open-channel blocker of hKv1.5 channel, presumably due to direct binding to specific amino acids within pore region of hKv1.5 channel, such as Thr479, Thr480, Val505, Ile508, Val512 and Val516. This blocking effect of verapamil on hKv1.5 channel appears to contribute at least partly to prolongation of atrial ERP and resultant antiarrhythmic action on atrial fibrillation in humans.

Photopharmacology is an area based on the creation of chemical compounds able to control the functioning of biological molecules using light. Photochromic compounds which activate or inhibit the activity of key cellular proteins, particularly ion channels, depending on the wavelength of the light, are powerful tools for noninvasive control of neural networks and, thus, for controlling the organs and behavior of animals. Photochromic substances can be divided into two main classes: (a) soluble photochromic ligands and (b) compounds covalently binding to target proteins, or tethered photochromic ligands. Potassium channel blockers, modulators of glutamate and GABA receptors, and cationic TRP channels have been created on this basis. Photopharmacology opens up the potential for controlling pain, restoring the photosensitivity of the retina, and controlling other physiological functions. This minireview will briefly present the main principles of the organization and actions of light-controlled switches, along with a description of photochromic chemical compounds able to modulate the activity of voltage-gated ion channels, and present preliminary investigations on the creation of photopharmacological compounds for therapeutic use.