Neuropathic pain is a chronic debilitating symptom characterized by spontaneous pain and mechanical allodynia. It occurs in distinct forms, including brush-evoked dynamic and filament-evoked punctate mechanical allodynia. Potassium channel 2.1 (Kir2.1), which exhibits strong inward rectification, is and regulates the activity of lamina I projection neurons. However, the relationship between Kir2.1 channels and mechanical allodynia is still unclear. In this study, we first found that pretreatment with ML133, a selective Kir2.1 inhibitor, by intrathecal administration, preferentially inhibited dynamic, but not punctate, allodynia in mice with spared nerve injury (SNI). Intrathecal injection of low doses of strychnine, a glycine receptor inhibitor, selectively induced dynamic, but not punctate allodynia, not only in naïve but also in ML133-pretreated mice. In contrast, bicuculline, a GABA receptor antagonist, induced only punctate, but not dynamic, allodynia. These results indicated the involvement of glycinergic transmission in the development of dynamic allodynia. We further found that SNI significantly suppressed the frequency, but not the amplitude, of the glycinergic spontaneous inhibitory postsynaptic currents (gly-sIPSCs) in neurons on the lamina II-III border of the spinal dorsal horn, and pretreatment with ML133 prevented the SNI-induced gly-sIPSC reduction. Furthermore, 5 days after SNI, ML133, either by intrathecal administration or acute bath perfusion, and strychnine sensitively reversed the SNI-induced dynamic, but not punctate, allodynia and the gly-sIPSC reduction in lamina IIi neurons, respectively. In conclusion, our results suggest that blockade of Kir2.1 channels in the spinal dorsal horn selectively inhibits dynamic, but not punctate, mechanical allodynia by enhancing glycinergic inhibitory transmission.
Animals ; Bicuculline ; pharmacology ; Disease Models, Animal ; Glycine ; metabolism ; Hyperalgesia ; drug therapy ; etiology ; metabolism ; Imidazoles ; pharmacology ; Inhibitory Postsynaptic Potentials ; drug effects ; physiology ; Male ; Mice, Inbred C57BL ; Neurons ; drug effects ; metabolism ; Neurotransmitter Agents ; pharmacology ; Peripheral Nerve Injuries ; drug therapy ; metabolism ; Phenanthrolines ; pharmacology ; Potassium Channels, Inwardly Rectifying ; antagonists & inhibitors ; metabolism ; Receptors, GABA-A ; metabolism ; Receptors, Glycine ; metabolism ; Strychnine ; pharmacology ; Synaptic Transmission ; drug effects ; physiology ; Tissue Culture Techniques ; Touch

OBJECTIVE: To observe the effect of cinobufagin on transient outward potassium current () in rat dorsal root ganglion cells of cancer-induced bone pain (CIBP) and explore the possible analgesic mechanism of cinobufagin. METHODS: Whole cell patch clamp technique was used to examine the effect of cionbufagin on in acutely isolated dorsal root ganglion (DRG) cells from normal SD rats and rats with bone cancer pain. RESULTS: The DRG cells from rats with CIBP showed obviously decreased current density, an activation curve shift to the right, and an inactivation curve shift to the left. Cinobufagin treatment significantly increased the current density and reversed the changes in the activation and inactivation curves in the DRG cells. CONCLUSIONS current is decreased in DRG neurons from rats with CIBP. Cinobufagin can regulate the activation and inactivation of current in the DRG cells, which may be related to its analgesic mechanism.
Analgesics ; pharmacology ; Animals ; Bufanolides ; pharmacology ; Cancer Pain ; drug therapy ; Cells, Cultured ; Ganglia, Spinal ; drug effects ; Patch-Clamp Techniques ; Potassium Channels ; metabolism ; Rats ; Rats, Sprague-Dawley

Cyproheptadine (CPH), a first-generation antihistamine, enhances the delayed rectifier outward K current (I) in mouse cortical neurons through a sigma-1 receptor-mediated protein kinase A pathway. In this study, we aimed to determine the effects of CPH on neuronal excitability in current-clamped pyramidal neurons in mouse medial prefrontal cortex slices. CPH (10 µmol/L) significantly reduced the current density required to generate action potentials (APs) and increased the instantaneous frequency evoked by a depolarizing current. CPH also depolarized the resting membrane potential (RMP), decreased the delay time to elicit an AP, and reduced the spike threshold potential. This effect of CPH was mimicked by a sigma-1 receptor agonist and eliminated by an antagonist. Application of tetraethylammonium (TEA) to block I channels hyperpolarized the RMP and reduced the instantaneous frequency of APs. TEA eliminated the effects of CPH on AP frequency and delay time, but had no effect on spike threshold or RMP. The current-voltage relationship showed that CPH increased the membrane depolarization in response to positive current pulses and hyperpolarization in response to negative current pulses, suggesting that other types of membrane ion channels might also be affected by CPH. These results suggest that CPH increases the excitability of medial prefrontal cortex neurons by regulating TEA-sensitive I channels as well as other TEA-insensitive K channels, probably I and inward-rectifier Kir channels. This effect of CPH may explain its apparent clinical efficacy as an antidepressant and antipsychotic.
Animals ; Cyproheptadine ; pharmacology ; Female ; Histamine H1 Antagonists ; pharmacology ; Membrane Potentials ; drug effects ; physiology ; Mice, Inbred C57BL ; Patch-Clamp Techniques ; Potassium Channel Blockers ; pharmacology ; Potassium Channels ; metabolism ; Prefrontal Cortex ; drug effects ; physiology ; Pyramidal Cells ; drug effects ; physiology ; Receptors, sigma ; agonists ; metabolism ; Tetraethylammonium ; pharmacology ; Tissue Culture Techniques

The hyphal development of Candida albicans (C. albicans) has been considered as an essential virulent factor for host cell damage. However, the missing link between hyphae and virulence of C. albicans is also been discovered. Here, we identified that the null mutants of ERG3 and ERG11, two key genes in ergosterol biosynthesis pathway, can form typical hyphae but failed to cause the oral mucosal infection in vitro and in vivo for the first time. In particular, the erg3Δ/Δ and erg11Δ/Δ strains co-cultured with epithelial cells significantly reduced the adhesion, damage, and cytokine (interleukin-1α (IL-1α)) production, whereas the invasion was not affected in vitro. Importantly, they were incapable of extensive hyphal invasion, formation of micro-abscesses, and tongue epithelium damage compared to wild type due to the decrease of the colonization and epithelial infection area in a murine oropharyngeal candidiasis model. The fluconazole (FLC), an antifungal targeted at ergosterol biosynthesis, relieved the epithelial infection of C. albicansin vitro and in vivo even under non-growth inhibitory dosage confirming the virulent contribution of ergosterol biosynthesis pathway. The erg3Δ/Δ and erg11Δ/Δ strains were cleared by macrophages similar to wild type, whereas their virulence factors including agglutinin-like sequence 1 (Als1), secreted aspartyl proteinase 6 (Sap6), and hyphal wall protein-1 (Hwp1) were significantly reduced indicated that the non-toxicity might not result from the change on immune tolerance but the defective virulence. The incapacity of erg3Δ/Δ and erg11Δ/Δ in epithelial infection highlights the contribution of ergosterol biosynthesis pathway to C. albicans pathogenesis and fluconazole can not only eliminate the fungal pathogens but also reduced their virulence even at low dosage.
Animals ; Antifungal Agents ; pharmacology ; Candida albicans ; drug effects ; genetics ; pathogenicity ; Candidiasis, Oral ; drug therapy ; genetics ; microbiology ; Fluconazole ; pharmacology ; Genes, Fungal ; genetics ; Mice ; Microscopy, Electron, Scanning ; Potassium Channels ; genetics ; Virulence

OBJECTIVETo investigate whether the methanol extract of Berberis amurensis Rupr. (BAR) augments penile erection using in vitro and in vivo experiments.

METHODSThe ex vivo study used corpus cavernosum strips prepared from adult male New Zealand White rabbits. In in vivo studies for intracavernous pressure (ICP), blood pressure, mean arterial pressure (MAP), and increase of peak ICP were continuously monitored during electrical stimulation of Sprague-Dawley rats.

RESULTSPreconstricted with phenylephrine (PE) in isolated endotheliumintact rabbit corus cavernosum, BAR relaxed penile smooth muscle in a dose-dependent manner, which was inhibited by pretreatment with NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, and H-[1,2,4]-oxadiazole-[4,3-α]-quinoxalin-1-one, a soluble guanylyl cclase inhibitor. BAR significantly relaxed penile smooth muscles dose-dependently in ex vivo, and this was inhibited by pretreatment with L-NAME H-[1,2,4]-oxadiazole-[4,3-α]-quinoxalin-1-one. BAR-induced relaxation was significantly attenuated by pretreatment with tetraethylammonium (TEA, P<0.01), a nonselective K channel blocker, 4-aminopyridine (4-AP, P<0.01), a voltage-dependent K channel blocker, and charybdotoxin (P<0.01), a large and intermediate conductance Ca sensitive-K channel blocker, respectively. BAR induced an increase in peak ICP, ICP/MAP ratio and area under the curve dose dependently.

CONCLUSIONBAR augments penile erection via the nitric oxide/cyclic guanosine monophosphate system and Ca sensitive-K (BK and IK) channels in the corpus cavernosum.

Animals ; Area Under Curve ; Berberis ; chemistry ; Blood Pressure ; drug effects ; Cyclic GMP ; metabolism ; Epoprostenol ; pharmacology ; In Vitro Techniques ; Indomethacin ; pharmacology ; Male ; Models, Biological ; Muscle Relaxation ; drug effects ; Muscle, Smooth ; drug effects ; physiology ; NG-Nitroarginine Methyl Ester ; pharmacology ; Nitric Oxide ; metabolism ; Penile Erection ; drug effects ; Phenylephrine ; pharmacology ; Plant Extracts ; pharmacology ; Potassium Channel Blockers ; pharmacology ; Potassium Channels ; metabolism ; Pressure ; Rabbits

PURPOSE: The mechanisms underlying repolarization abnormalities during pregnancy are not fully understood. Although maternal serotonin (5-hydroxytryptamine, 5-HT) production is an important determinant for normal fetal development in mice, its role in mothers remains unclear. We evaluated the role of serotonin in ventricular repolarization in mice hearts via 5Htr3 receptor (Htr3a) and investigated the mechanism of QT-prolongation during pregnancy. MATERIALS AND METHODS: We measured current amplitudes and the expression levels of voltage-gated K⁺ (Kv) channels in freshly-isolated left ventricular myocytes from wild-type non-pregnant (WT-NP), late-pregnant (WT-LP), and non-pregnant Htr3a homozygous knockout mice (Htr3a(−/−)-NP). RESULTS: During pregnancy, serotonin and tryptophan hydroxylase 1, a rate-limiting enzyme for the synthesis of serotonin, were markedly increased in hearts and serum. Serotonin increased Kv current densities concomitant with the shortening of the QT interval in WT-NP mice, but not in WT-LP and Htr3a(−/−)-NP mice. Ondansetron, an Htr3 antagonist, decreased Kv currents in WT-LP mice, but not in WT-NP mice. Kv4.3 directly interacted with Htr3a, and this binding was facilitated by serotonin. Serotonin increased the trafficking of Kv4.3 channels to the cellular membrane in WT-NP. CONCLUSION: Serotonin increases repolarizing currents by augmenting Kv currents. Elevated serotonin levels during pregnancy counterbalance pregnancy-related QT prolongation by facilitating Htr3-mediated Kv currents.
*Action Potentials/drug effects ; Animals ; Cell Membrane/drug effects/metabolism ; Disease Models, Animal ; Electrocardiography ; Female ; HSC70 Heat-Shock Proteins/metabolism ; HSP90 Heat-Shock Proteins/metabolism ; Heart Ventricles/drug effects/*metabolism ; Mice, Inbred C57BL ; Mice, Knockout ; Myocytes, Cardiac/drug effects/metabolism ; Potassium Channels/metabolism ; Pregnancy ; Rabbits ; Rats, Sprague-Dawley ; Receptors, Serotonin, 5-HT3/metabolism ; Serotonin/*metabolism ; Serotonin 5-HT3 Receptor Agonists/pharmacology

The present study attempted to test a novel hypothesis that Ca(2+) sparks play an important role in arterial relaxation induced by tacrolimus. Recorded with confocal laser scanning microscopy, tacrolimus (10 µmol/L) increased the frequency of Ca(2+) sparks, which could be reversed by ryanodine (10 µmol/L). Electrophysiological experiments revealed that tacrolimus (10 µmol/L) increased the large-conductance Ca(2+)-activated K(+) currents (BKCa) in rat aortic vascular smooth muscle cells (AVSMCs), which could be blocked by ryanodine (10 µmol/L). Furthermore, tacrolimus (10 and 50 µmol/L) reduced the contractile force induced by norepinephrine (NE) or KCl in aortic vascular smooth muscle in a concentration-dependent manner, which could be also significantly attenuated by iberiotoxin (100 nmol/L) and ryanodine (10 µmol/L) respectively. In conclusion, tacrolimus could indirectly activate BKCa currents by increasing Ca(2+) sparks released from ryanodine receptors, which inhibited the NE- or KCl-induced contraction in rat aorta.
Animals ; Aorta ; cytology ; metabolism ; physiology ; Calcium Signaling ; Cells, Cultured ; Large-Conductance Calcium-Activated Potassium Channels ; metabolism ; Male ; Muscle, Smooth, Vascular ; drug effects ; metabolism ; physiology ; Myocytes, Smooth Muscle ; drug effects ; metabolism ; Norepinephrine ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Ryanodine ; pharmacology ; Tacrolimus ; pharmacology ; Vasoconstriction

OBJECTIVETo assess the biological effects of the six-herb mixture Anti-Insomia Formula (AIF) extract using caffeine-induced insomnia Drosophila model and short-sleep mutants.

METHODSCaffeineinduced insomnia wild-type Drosophila and short-sleep mutant flies minisleep (mns) and Hyperkinetic(Y) (Hk(Y)) were used to assess the hypnotic effects of the AIF in vivo. The night time activity, the amount of night time sleep and the number of sleep bouts were determined using Drosophila activity monitoring system. Sleep was defined as any period of uninterrupted behavioral immobility (0 count per minute) lasting > 5 min. Night time sleep was calculated by summing up the sleep time in the dark period. Number of sleep bouts was calculated by counting the number of sleep episodes in the dark period.

RESULTSAIF at the dosage of 50 mg/mL, effectively attenuated caffeine-induced wakefulness (P<0.01) in wild-type Canton-S flies as indicated by the reduction of the sleep bouts, night time activities and increase of the amount of night time sleep. AIF also significantly reduced sleeping time of short-sleep Hk(Y) mutant flies (P<0.01). However, AIF did not produce similar effect in mns mutants.

CONCLUSIONAIF might be able to rescue the abnormal condition caused by mutated modulatory subunit of the tetrameric potassium channel, but not rescuing the abnormal nerve firing caused by Shaker gene mutation. This study provides the scientific evidence to support the use of AIF in Chinese medicine for promoting sleep quality in insomnia.

Animals ; Caffeine ; Chromatography, High Pressure Liquid ; Disease Models, Animal ; Drosophila melanogaster ; drug effects ; physiology ; Hypnotics and Sedatives ; pharmacology ; therapeutic use ; Mutation ; genetics ; Potassium Channels ; genetics ; Sleep ; drug effects ; Sleep Initiation and Maintenance Disorders ; drug therapy ; Wakefulness ; drug effects

Chloroquine ; pharmacology ; Down-Regulation ; Gene Expression ; drug effects ; HEK293 Cells ; Humans ; Leupeptins ; pharmacology ; Membrane Proteins ; antagonists & inhibitors ; genetics ; metabolism ; Microscopy, Fluorescence ; Protein Binding ; Protein Subunits ; genetics ; metabolism ; RNA Interference ; RNA, Small Interfering ; metabolism ; Shab Potassium Channels ; genetics ; metabolism

OBJECTIVETo observe the neurological protective effects of progesterone (PROG) on focal cerebral ischemia/reperfusion injury in rats and to explore its possible mechanism.

METHODSOne handred and twenty male SD rats were divided into three groups randomly: sham-operated group, middle cerebral artery occlusion ( MCAO ) group and PROG + MCAO group( n = 40). The right temporary MCAO model was established by the line-embolism method. The PROG + MCAO group rats were according to 8 mg/kg intraperitoneal injection PROG, after that 30 min, the rats were suffered ischemia/reperfusion. After rats were suffered ischemia for 2 h and reperfusion 0, 24, 48, 72 h stress, the nervous functional defect degree were evaluated by longe scoring, and the expression of two-pore domain K channel 3 (TASK3) mRNA in brain tissue were detected by the real-time PCR.

RESULTSPROG (8 mg/kg) could significantly reduced the nervous functional defect degree in rats after ischemia/reperfusion 24, 48, 72 h (P < 0.05). The results of real-time PCR showed that the TASK3 mRNA expression in the brain tissue at all time points significantly decreased in MCAO group compared with sham-operated group (P < 0.05). However, compared with MCAO group, the expression of TASK3 mRNA in brain tissue at all time points dramatically increased in PROG + MCAO group (P < 0.05).

CONCLUSIONPROG can improve the nervous functional defect degree after focal cerebral ischemia/reperfusion injury in rats, and the mechanism might be associated with up-regulating the expression of TASK3 mRNA in brain tissue.

Animals ; Brain ; drug effects ; pathology ; Brain Ischemia ; drug therapy ; Infarction, Middle Cerebral Artery ; Male ; Neuroprotective Agents ; pharmacology ; Potassium Channels, Tandem Pore Domain ; metabolism ; Progesterone ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Real-Time Polymerase Chain Reaction ; Reperfusion Injury ; drug therapy