Quercetin mainly exists in the skin of colored fruits and vegetables as one of flavonoids. Recent studies show that quercetin, like other flavonoids, has diverse pharmacological actions. However, relatively little is known about quercetin effects in the regulations of ligand-gated ion channels. In the previous reports, we have shown that quercetin regulates subsets of homomeric ligand-gated ion channels such as glycine, 5-HT3A and alpha7 nicotinic acetylcholine receptors. In the present study, we examined quercetin effects on heteromeric neuronal alpha3beta4 nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding bovine neuronal alpha3 and beta4 subunits. Treatment with acetylcholine elicited an inward peak current (IACh) in oocytes expressing alpha3beta4 nicotinic acetylcholine receptor. Co-treatment with quercetin and acetylcholine inhibited IACh in oocytes expressing alpha3beta4 nicotinic acetylcholine receptors. The inhibition of IACh by quercetin was reversible and concentration-dependent. The half-inhibitory concentration (IC50) of quercetin was 14.9+/-0.8 microM in oocytes expressing alpha3beta4 nicotinic acetylcholine receptor. The inhibition of IACh by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate alpha3beta4 nicotinic acetylcholine receptor and this regulation might be one of the pharmacological actions of quercetin in nervous systems.
Acetylcholine ; Flavonoids ; Fruit ; Glycine ; Ligand-Gated Ion Channels ; Nervous System ; Neurons ; Oocytes ; Quercetin ; Receptors, Nicotinic ; RNA, Complementary ; Skin ; Social Control, Formal ; Vegetables ; Xenopus

BACKGROUND: Both ondansetron and granisetron exert their antiemetic effects via a blockade of the 5-hydroxytryptamine 3 receptor (5-HT(3)R). Because the 5-HT(3)R is a member of a superfamily of ligand-gated ion channels and has structural similarities to the nicotinic acetylcholine receptor (nAChR), a 5-HT(3)R antagonist may also inhibit the nAChR. This study examined the effects of 5-HT(3)R antagonists, ondansetron and granisetron, on rocuronium-induced neuromuscular blockade in vitro. METHODS: Rat phrenic nerve-hemidiaphragm preparations were isolated and allocated randomly into seven groups (control, 1, 10, 100 microgram/ml of ondansetron, 0.1, 1, 10 microgram/ml of granisetron). Two studies were carried out using single twitch responses. In the cumulative dose-response study, rocuronium 1 microgram/ml and each doses of ondansetron or granisetron were administered simultaneously, and incremental 0.5 microgram/ml doses of rocuronium were added to obtain more than 95% neuromuscular twitch inhibition. ED(5), ED(50), ED(90), and ED(95) of rocuronium in each group were calculated using a logistic model. In the partial curarization study, the twitch heights were measured after administering ondansetron or granisetron (10 minutes after administering 3 microgram/ml rocuronium) and were measured 10 minutes later. The 2 twitch heights were then compared. RESULTS: In the cumulative dose-response study, ondansetron 100 microgram/ml and granisetron 10 microgram/ml significantly reduced the ED50 of rocuronium (P < 0.05). There were no intergroup differences in the partial curarization study. CONCLUSIONS: High concentration of ondansetron and granisetron enhanced the neuromuscular blockade of rocuronium. Granisetron enhanced the neuromuscular blockade of rocuronium more potently than ondansetron.
Animals ; Antiemetics ; Drug Interactions ; Granisetron* ; Ligand-Gated Ion Channels ; Logistic Models ; Neuromuscular Blockade* ; Ondansetron* ; Rats* ; Receptors, Nicotinic ; Serotonin

BACKGROUND: The 5-hydroxytryptamine type 3 (5-HT3) receptor is a member of the Cys-loop superfamily of ligand-gated ion channels (LGICs) and modulated by pharmacologic relevant concentrations of volatile anesthetics or n-alcohols like most receptors of LGICs. The goal of this study was to reveal whether the site-directed single mutations of E-106, F-107 and R-222 in 5-HT3 receptor may affect the anesthetic modulation of halothane known as positive modulator. METHODS: The wild-type and mutant receptors, E106D, F107Y, R222F, R222V, were expressed in Xenopus Laevis oocytes and receptor function was assessed using two electrode voltage clamp techniques. RESULTS: E106D, F107Y, R222F, R222V mutant 5-HT3A receptors were functionally expressed. F107Y mutant 5-HT3A receptors displayed decreased sensitivity to 5-HT compared to the wild type 5-HT3A receptor (P < 0.05). Halothane showed positive modulation in both wild and F107Y mutant 5-HT3A receptors but F107Y mutant 5-HT3 receptor showed greater enhancing modulation comparing to wild-type receptor. Meanwhile, R222F and R222V mutant 5-HT3 receptor lost positive modulation with 1 and 2 MAC of halothane. Most interestingly, positive modulation by halothane was converted into negative modulation in E106D mutant 5-HT3A receptor. CONCLUSIONS: The present study implicate the amino acid residues known for agonist binding and linking agonist binding to channel gating might also have important role for anesthetic modulation in 5-HT3A receptor.
Anesthetics ; Electrodes ; Electrophysiology ; Halothane ; Ligand-Gated Ion Channels ; Oocytes ; Patch-Clamp Techniques ; Receptors, Serotonin, 5-HT3 ; Serotonin ; Xenopus laevis

Resveratrol is a phytoalexin found in grapes, red wine, and berries. Resveratrol has been known to have many beneficial health effects, such as anti-cancer, neuroprotective, anti-inflammatory, and life-prolonging effects. However, relatively little is known about the effects of resveratrol on the regulation of ligand-gated ion channels. We have previously reported that resveratrol regulates subsets of homomeric ligand-gated ion channels such as those of 5-HT3A receptors. The gamma-aminobutyric acidC (GABAC) receptor is mainly expressed in retinal bipolar cells and plays an important role in visual processing. In the present study, we examined the effects of resveratrol on the channel activity of homomeric GABAC receptor expressed in Xenopus oocytes injected with cRNA encoding human GABAC rho subunits. Our data show that the application of GABA elicits an inward peak current (IGABA) in oocytes that express the GABAC receptor. Resveratrol treatment had no effect on oocytes injected with H2O or with GABAC receptor cRNA. Co-treatment with resveratrol and GABA inhibited IGABA in oocytes with GABAC receptors. The inhibition of IGABA by resveratrol was in a reversible and concentration-dependent manner. The IC50 of resveratrol was 28.9+/-2.8 microM in oocytes expressing GABAC receptor. The inhibition of IGABA by resveratrol was in voltage-independent and non-competitive manner. These results indicate that resveratrol might regulate GABAC receptor expression and that this regulation might be one of the pharmacological actions of resveratrol on the nervous system.
Fruit ; gamma-Aminobutyric Acid ; Humans ; Inhibitory Concentration 50 ; Ligand-Gated Ion Channels ; Nervous System ; Oocytes ; Receptors, GABA ; Retinal Bipolar Cells ; RNA, Complementary ; Sesquiterpenes ; Stilbenes ; Vitis ; Wine ; Xenopus

The medial vestibular nucleus (MVN) neurons are controlled by excitatory synaptic transmission from the vestibular afferent and commissural projections, and by inhibitory transmission from interneurons. Spontaneous synaptic currents of MVN neurons were studied using whole cell patch clamp recording in slices prepared from 13- to 17-day-old rats. The spontaneous inhibitory postsynaptic currents (sIPSCs) were significantly reduced by the GABAA antagonist bicuculline (20micrometer), but were not affected by the glycine antagonist strychnine (1micrometer). The frequency, amplitude, and decay time constant of sIPSCs were 4.3 0.9 Hz, 18.1 2.0 pA, and 8.9 0.4 ms, respectively. Spontaneous excitatory postsynaptic currents (sEPSCs) were mediated by non-NMDA and NMDA receptors. The specific AMPA receptor antagonist GYKI-52466 (50micrometer) completely blocked the non-NMDA mediated sEPSCs, indicating that they are mediated by an AMPA-preferring receptor. The AMPA mediated sEPSCs were characterized by low frequency (1.5 0.4 Hz), small amplitude (13.9 1.9 pA), and rapid decay kinetics (2.8 0.2 ms). The majority (15/21) displayed linear I-V relationships, suggesting the presence of GluR2-containing AMPA receptors. Only 35% of recorded MVN neurons showed NMDA mediated currents, which were characterized by small amplitude and low frequency. These results suggest that the MVN neurons receive excitatory inputs mediated by AMPA, but not kainate, and NMDA receptors, and inhibitory transmission mediated by GABAA receptors in neonatal rats.
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid ; Animals ; Bicuculline ; Excitatory Postsynaptic Potentials* ; Glycine ; Inhibitory Postsynaptic Potentials ; Interneurons ; Kainic Acid ; Kinetics ; N-Methylaspartate ; Neurons* ; Rats* ; Receptors, AMPA ; Receptors, N-Methyl-D-Aspartate ; Strychnine ; Synaptic Transmission ; Vestibular Nuclei*

BACKGROUND: The 5-hydroxytryptamine 3 receptor (5-HT3R) is a member of a superfamily of ligand-gated ion channels which has structural similarities and common evolutionary origin to those of the nicotinic acetylcholine receptor (nAChR). 5-hydroxytryptamine (5-HT) and muscle relaxants may have cross reaction. Rocuronium is a non-depolarizing neuromuscular blocking agent which has a rapid onset. The aim of this study was to examined the effects of 5-HT on rocuronium-induced neuromuscular blockade in a rat phrenic nerve-hemidiaphragm preparation. METHODS: Institutional approval was obtained for the experimental procedure. Fifty male Sprague-Dawley rats (150-200 g) were divided into 5 groups; the control, and 0.1, 1, 10, and 20microgram/ml of 5-HT. The animals were injected with phentobarbital at 40 mg/kg into the peritoneal cavity. The hemidiaphragm with the phrenic nerve was dissected and then mounted in a bath containing 100 ml Krebs solution at room temperature. The phrenic nerve was stimulated at the supramaximal intensity using a Grass(R) S88 stimulator via an SIU5 isolation unit. The twitch height was measured and recorded using a precalibrated Grass(R) FT88 force displacement transducer and recorded with a Grass(R) 79 polygraph, respectively. In the cumulative dose-response study, the rocuronium 100microgram/dl and each dose of 5-HT were administered simultaneously administered, with additional 50microgram/dl incremental doses of rocuronium were added to obtain grteater than 95% neuromuscular twitch inhibition. The ED5, ED50, ED90, and ED95 of rocuronium in each group were calculated using a probit model. RESULTS: The ED50, ED90, and ED95 of rocuronium were significantly reduced in 5-HT 20microgram/ml group (P < 0.05), but no differences were observed with the other 5-HT groups compared to the control groups. CONCLUSIONS: 5-HT at 20microgram/ml enhanced the neuromuscular blockade of rocuronium.
Animals ; Baths ; Cross Reactions ; Humans ; Ligand-Gated Ion Channels ; Male ; Neuromuscular Blockade* ; Peritoneal Cavity ; Phrenic Nerve ; Rats* ; Rats, Sprague-Dawley ; Receptors, Nicotinic ; Serotonin* ; Transducers

The flavonoid quercetin is a low molecular weight compound generally found in apple, gingko, tomato, onion and other red-colored fruits and vegetables. Like other flavonoids, quercetin has diverse pharmacological actions. However, relatively little is known about the influence of quercetin effects in the regulation of ligand-gated ion channels. Previously, we reported that quercetin regulates subsets of nicotinic acetylcholine receptors such as alpha3beta4, alpha7 and alpha9alpha10. Presently, we investigated the effects of quercetin on muscle-type of nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding human fetal or adult muscle-type of nicotinic acetylcholine receptor subunits. Acetylcholine treatment elicited an inward peak current (IACh) in oocytes expressing both muscle-type of nicotinic acetylcholine receptors and co-treatment of quercetin with acetylcholine inhibited IACh. Pre-treatment of quercetin further inhibited IACh in oocytes expressing adult and fetal muscle-type nicotinic acetylcholine receptors. The inhibition of IACh by quercetin was reversible and concentration-dependent. The IC50 of quercetin was 18.9+/-1.2 microM in oocytes expressing adult muscle-type nicotinic acetylcholine receptor. The inhibition of IACh by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate human muscle-type nicotinic acetylcholine receptor channel activity and that quercetin-mediated regulation of muscle-type nicotinic acetylcholine receptor might be coupled to regulation of neuromuscular junction activity.
Acetylcholine ; Adult ; Flavonoids ; Fruit ; Ginkgo biloba ; Humans ; Inhibitory Concentration 50 ; Ligand-Gated Ion Channels ; Lycopersicon esculentum ; Molecular Weight ; Neuromuscular Junction ; Onions ; Oocytes ; Quercetin ; Receptors, Nicotinic ; RNA, Complementary ; Vegetables ; Xenopus

Visceral pain is the most common form of pain caused by varied diseases and a major reason for patients to seek medical consultation. It also leads to a significant economic burden due to workdays lost and reduced productivity. Further, long-term use of non-specific medications is also associated with side effects affecting the quality of life. Despite years of extensive research and the availability of several therapeutic options, management of patients with chronic visceral pain is often inadequate, resulting in frustration for both patients and physicians. This is, most likely, because the mechanisms associated with chronic visceral pain are different from those of acute pain. Accumulating evidence from years of research implicates several receptors and ion channels in the induction and maintenance of central and peripheral sensitization during chronic pain states. Understanding the specific role of these receptors will facilitate to capitalize on their unique properties to augment the therapeutic efficacy while at the same time minimizing unwanted side effects. The aim of this review is to provide a concise review of the recent literature that reports on the role of principal ionotropic receptors and metabotropic receptors in the modulation visceral pain. We also include an overview of the possibility of these receptors as potential new targets for the treatment of chronic visceral pain conditions.
Acute Pain ; Chronic Pain ; Efficiency ; Frustration ; Humans ; Ion Channels ; Ligand-Gated Ion Channels ; Quality of Life ; Receptors, Metabotropic Glutamate ; Visceral Pain*

Ca2+ influx appears to be important for triggering myoblast fusion. It remains, however, unclear how Ca2+ influx rises prior to myoblast fusion. Recently, several studies suggested that NMDA receptors may be involved in Ca2+ mobilization of muscle, and that Ca2+ influx is mediated by NMDA receptors in C2C12 myoblasts. Here, we report that other types of ionotropic glutamate receptors, non-NMDA receptors (AMPA and KA receptors), are also involved in Ca2+ influx in myoblasts. To explore which subtypes of non-NMDA receptors are expressed in C2C12 myogenic cells, RT-PCR was performed, and the results revealed that KA receptor subunits were expressed in both myoblasts and myotubes. However, AMPA receptor was not detected in myoblasts but expressed in myotubes. Using a Ca2+ imaging system, Ca2+ influx mediated by these receptors was directly measured in a single myoblast cell. Intracellular Ca2+ level was increased by KA, but not by AMPA. These results were consistent with RT-PCR data. In addition, KA-induced intracellular Ca2+ increase was completely suppressed by treatment of nifedifine, a L-type Ca2+ channel blocker. Furthermore, KA stimulated myoblast fusion in a dose-dependent manner. CNQX inhibited not only KA-induced myoblast fusion but also spontaneous myoblast fusion. Therefore, these results suggest that KA receptors are involved in intracellular Ca2+ increase in myoblasts and then may play an important role in myoblast fusion.
6-Cyano-7-nitroquinoxaline-2,3-dione ; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid ; Kainic Acid* ; Muscle Fibers, Skeletal ; Myoblasts ; Receptors, AMPA ; Receptors, Ionotropic Glutamate ; Receptors, Kainic Acid* ; Receptors, N-Methyl-D-Aspartate

Noxious stimuli in the esophagus activate nociceptive receptors on esophageal mucosa, such as transient receptor potential, acid-sensing ion channel and the P2X family, a family of ligand-gated ion channels responsive to ATP, and this generates signals that are transmitted to the central nervous system via either spinal nerves or vagal nerves, resulting in esophageal sensation. Among the noxious stimuli, gastric acid and other gastric contents are clinically most important, causing typical reflux symptoms such as heartburn and regurgitation. A conventional acid penetration theory has been used to explain the mechanism of heartburn, but much recent evidence does not support this theory. Therefore, it may be necessary to approach the causes of heartburn symptoms from a new conceptual framework. Hypersensitivity of the esophagus, like that of other visceral organs, includes peripheral, central and probably psychosocial factor-mediated hypersensitivity, and is known to play crucial roles in the pathoegenesis of nonerosive reflux disease, functional heartburn and non-cardiac chest pain. There also are esophagitis patients who do not perceive typical symptoms. This condition is known as silent gastroesophageal reflux disease. Although the pathogenesis of silent gastroesophageal reflux disease is still not known, hyposensitivity to reflux of acid may possibly explain the condition.
Adenosine Triphosphate ; Central Nervous System ; Chest Pain ; Esophagitis ; Esophagus ; Gastric Acid ; Gastroesophageal Reflux ; Heartburn ; Humans ; Hypersensitivity ; Ion Channels ; Ligand-Gated Ion Channels ; Mucous Membrane ; Nociceptors ; Sensation ; Spinal Nerves