RESUMEN
Pyrethroids are widely used against agricultural pests and human disease vectors due to their broad insecticidal spectrum, fast action, and low mammalian toxicity. Unfortunately, overuse of pyrethroids has led to knockdown resistance (kdr) caused by mutations in voltage-gated sodium channels. Mutation I1011M was repeatedly detected in numerous pyrethroid-resistant Aedes aegypti populations from Latin American and Brazil. In addition, mutation G923V was first reported to coexist with I1011M in permethrin/DDT-resistant Ae. aegypti, whether G923V enhances the I1011M-mediated pyrethroid resistance in sodium channels remains unclear. In this study, we introduced mutations G923V and I1011M alone or in combination into the pyrethroid-sensitive sodium channel AaNav1-1 and examined the effects of these mutations on gating properties and pyrethroid sensitivity. We found mutations I1011M and G923V + I1011M shifted the voltage dependence of activation in the depolarizing direction, and none of mutations affect the voltage-dependence of inactivation. G923V and G923V + I1011M mutations reduced the channel sensitivity to both Type I and Type II pyrethroids. However, I1011M alone conferred resistance to Type I pyrethroids, not to Type II pyrethroids. Interestingly, significant synergism effects on Type I pyrethroids were observed between mutations G923V and I1011M. The effects of all mutations on channel sensitivity to DDT were identical with those to Type I pyrethroids. Our results confirm the molecular basis of resistance mediated by mutations G923V and I1011M and may contribute to develop molecular markers for monitoring pest resistance to pyrethroids.
Asunto(s)
Aedes , Resistencia a los Insecticidas , Insecticidas , Piretrinas , Piretrinas/farmacología , Animales , Resistencia a los Insecticidas/genética , Aedes/genética , Aedes/efectos de los fármacos , Insecticidas/farmacología , Glicina/farmacología , Glicina/análogos & derivados , Canales de Sodio/genética , Canales de Sodio/metabolismo , Canales de Sodio/efectos de los fármacos , Valina/genética , Mutación , Sustitución de Aminoácidos , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Dominios ProteicosRESUMEN
The lateral parabrachial nucleus (PBL) is implicated in the regulation of respiratory activity. Sodium leak channel (NALCN) mutations disrupt the respiratory rhythm and influence anesthetic sensitivity in both rodents and humans. Here, we investigated whether the NALCN in PBL glutamatergic neurons maintains respiratory function under general anesthesia. Our results showed that chemogenetic activation of PBL glutamatergic neurons increased the respiratory frequency (RF) in mice; whereas chemogenetic inhibition suppressed RF. NALCN knockdown in PBL glutamatergic neurons but not GABAergic neurons significantly reduced RF under physiological conditions and caused more respiratory suppression under sevoflurane anesthesia. NALCN knockdown in PBL glutamatergic neurons did not further exacerbate the respiratory suppression induced by propofol or morphine. Under sevoflurane anesthesia, painful stimuli rapidly increased the RF, which was not affected by NALCN knockdown in PBL glutamatergic neurons. This study suggested that the NALCN is a key ion channel in PBL glutamatergic neurons that maintains respiratory frequency under volatile anesthetic sevoflurane but not intravenous anesthetic propofol.
Asunto(s)
Anestésicos por Inhalación , Neuronas , Núcleos Parabraquiales , Sevoflurano , Sevoflurano/farmacología , Animales , Núcleos Parabraquiales/efectos de los fármacos , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Anestésicos por Inhalación/farmacología , Ratones , Masculino , Canales de Sodio/efectos de los fármacos , Canales de Sodio/metabolismo , Propofol/farmacología , Ácido Glutámico/metabolismo , Ratones Endogámicos C57BL , Frecuencia Respiratoria/efectos de los fármacos , Respiración/efectos de los fármacos , Canales Iónicos , Proteínas de la MembranaRESUMEN
BACKGROUND: Stimulation of the paraventricular thalamus has been found to enhance anesthesia recovery; however, the underlying molecular mechanism by which general anesthetics modulate paraventricular thalamus is unclear. This study aimed to test the hypothesis that the sodium leak channel (NALCN) maintains neuronal activity in the paraventricular thalamus to resist anesthetic effects of sevoflurane in mice. METHODS: Chemogenetic and optogenetic manipulations, in vivo multiple-channel recordings, and electroencephalogram recordings were used to investigate the role of paraventricular thalamus neuronal activity in sevoflurane anesthesia. Virus-mediated knockdown and/or overexpression was applied to determine how NALCN influenced excitability of paraventricular thalamus glutamatergic neurons under sevoflurane. Viral tracers and local field potentials were used to explore the downstream pathway. RESULTS: Single neuronal spikes in the paraventricular thalamus were suppressed by sevoflurane anesthesia and recovered during emergence. Optogenetic activation of paraventricular thalamus glutamatergic neurons shortened the emergence period from sevoflurane anesthesia, while chemogenetic inhibition had the opposite effect. Knockdown of the NALCN in the paraventricular thalamus delayed the emergence from sevoflurane anesthesia (recovery time: from 24 ± 14 to 64 ± 19 s, P < 0.001; concentration for recovery of the righting reflex: from 1.13% ± 0.10% to 0.97% ± 0.13%, P < 0.01). As expected, the overexpression of the NALCN in the paraventricular thalamus produced the opposite effects. At the circuit level, knockdown of the NALCN in the paraventricular thalamus decreased the neuronal activity of the nucleus accumbens, as indicated by the local field potential and decreased single neuronal spikes in the nucleus accumbens. Additionally, the effects of NALCN knockdown in the paraventricular thalamus on sevoflurane actions were reversed by optical stimulation of the nucleus accumbens. CONCLUSIONS: Activity of the NALCN maintains the excitability of paraventricular thalamus glutamatergic neurons to resist the anesthetic effects of sevoflurane in mice.
Asunto(s)
Anestésicos por Inhalación , Núcleos Talámicos de la Línea Media , Neuronas , Sevoflurano , Animales , Sevoflurano/farmacología , Ratones , Anestésicos por Inhalación/farmacología , Neuronas/efectos de los fármacos , Neuronas/fisiología , Núcleos Talámicos de la Línea Media/efectos de los fármacos , Núcleos Talámicos de la Línea Media/fisiología , Masculino , Ratones Endogámicos C57BL , Canales de Sodio/efectos de los fármacos , Canales de Sodio/fisiología , Ácido Glutámico/metabolismo , Ácido Glutámico/farmacología , Canales Iónicos , Proteínas de la MembranaRESUMEN
Bile acids (BAs) are known to be important regulators of intestinal motility and epithelial fluid and electrolyte transport. Over the past two decades, significant advances in identifying and characterizing the receptors, transporters, and ion channels targeted by BAs have led to exciting new insights into the molecular mechanisms involved in these processes. Our appreciation of BAs, their receptors, and BA-modulated ion channels as potential targets for the development of new approaches to treat intestinal motility and transport disorders is increasing. In the current review, we aim to summarize recent advances in our knowledge of the different BA receptors and BA-modulated ion channels present in the gastrointestinal system. We discuss how they regulate motility and epithelial transport, their roles in pathogenesis, and their therapeutic potential in a range of gastrointestinal diseases.
Asunto(s)
Ácidos y Sales Biliares/metabolismo , Tracto Gastrointestinal/efectos de los fármacos , Canales Iónicos/efectos de los fármacos , Hígado/efectos de los fármacos , Humanos , Canales Iónicos/agonistas , Receptores de Calcitriol/efectos de los fármacos , Canales de Sodio/efectos de los fármacosRESUMEN
Many human cardiovascular and neurological disorders (such as ischemia, epileptic seizures, traumatic brain injury, neuropathic pain, etc.) are associated with the abnormal functional activity of voltage-gated sodium channels (VGSCs/NaVs). Many natural toxins, including the sea anemone toxins (called neurotoxins), are an indispensable and promising tool in pharmacological researches. They have widely been carried out over the past three decades, in particular, in establishing different NaV subtypes functional properties and a specific role in various pathologies. Therefore, a large number of publications are currently dedicated to the search and study of the structure-functional relationships of new sea anemone natural neurotoxins-potential pharmacologically active compounds that specifically interact with various subtypes of voltage gated sodium channels as drug discovery targets. This review presents and summarizes some updated data on the structure-functional relationships of known sea anemone neurotoxins belonging to four structural types. The review also emphasizes the study of type 2 neurotoxins, produced by the tropical sea anemone Heteractis crispa, five structurally homologous and one unique double-stranded peptide that, due to the absence of a functionally significant Arg14 residue, loses toxicity but retains the ability to modulate several VGSCs subtypes.
Asunto(s)
Venenos de Cnidarios , Neurotoxinas , Anémonas de Mar , Canales de Sodio , Animales , Humanos , Venenos de Cnidarios/toxicidad , Neurotoxinas/toxicidad , Neurotoxinas/química , Péptidos , Anémonas de Mar/química , Canales de Sodio/efectos de los fármacosRESUMEN
OBJECTIVE: Volatile anesthetics are widely used for general anesthesia during surgical operations. Voltage-gated Na+ channels expressed in central neurons are major targets for volatile anesthetics; but it is unclear whether these drugs modulate native tetrodotoxin-resistant (TTX-R) Na+ channels, which are involved in the development and maintenance of inflammatory pain. METHODS: In this study, we examined the effects of sevoflurane on TTX-R Na+ currents (INa) in acutely isolated rat dorsal root ganglion neurons, using a whole-cell patch-clamp technique. RESULTS: Sevoflurane slightly potentiated the peak amplitude of transient TTX-R INa but more potently inhibited slow voltage-ramp-induced persistent INa in a concentration-dependent manner. Sevoflurane (0.86 ± 0.02 mM) (1) slightly shifted the steady-state fast inactivation relationship to hyperpolarizing ranges without affecting the voltage-activation relationship, (2) reduced the extent of use-dependent inhibition of Na+ channels, (3) accelerated the onset of inactivation and (4) delayed the recovery from inactivation of TTX-R Na+ channels. Thus, sevoflurane has diverse effects on TTX-R Na+ channels expressed in nociceptive neurons. CONCLUSIONS: The present results suggest that the inhibition of persistent INa and the modulation of the voltage dependence and inactivation might be, at least in part, responsible for the analgesic effects elicited by sevoflurane.
Asunto(s)
Anestésicos por Inhalación/farmacología , Ganglios Espinales/citología , Nociceptores/efectos de los fármacos , Sevoflurano/farmacología , Canales de Sodio/efectos de los fármacos , Animales , Potenciales de la Membrana , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Nociceptores/metabolismo , Técnicas de Placa-Clamp , Ratas , Canales de Sodio/metabolismo , Tetrodotoxina , Canales de Sodio Activados por Voltaje/efectos de los fármacos , Canales de Sodio Activados por Voltaje/metabolismoRESUMEN
Propranolol, a representative adrenergic ß-receptor antagonist, is widely used to prevent migraine attacks. Although propranolol is well known to inhibit tetrodotoxin-resistant (TTX-R) Na+ channels in cardiac myocytes, it is unclear whether the drug modulates these channels expressed in dural afferent neurons. In this study, we examined the effects of propranolol on TTX-R Na+ channels in medium-sized dural afferent neurons identified by the fluorescent dye DiI. The TTX-R Na+ currents (INa) were recorded from acutely isolated DiI-positive neurons using a whole-cell patch clamp technique under voltage-clamp conditions. Propranolol inhibited the noninactivating steady-state component more potently than the peak component of transient TTX-R INa. Propranolol also potently inhibited the slow voltage ramp-induced TTX-R INa in a concentration-dependent manner, suggesting that it preferentially inhibited the noninactivating or persistent INa in DiI-positive neurons. Propranolol had little effect on voltage dependence, but it increased the extent of the use-dependent inhibition of TTX-R Na+ channels. Propranolol also accelerated the onset of inactivation and retarded recovery from inactivation in these channels. Under current-clamp conditions, propranolol decreased the number of action potentials elicited by depolarizing current stimuli. In conclusion, the propranolol-mediated preferential inhibition of persistent INa and modulation of the inactivation kinetics of TTX-R Na+ channels might represent additional mechanisms for migraine prophylaxis.
Asunto(s)
Neuronas Aferentes/metabolismo , Neuronas/efectos de los fármacos , Propranolol/farmacología , Bloqueadores de los Canales de Sodio/farmacología , Canales de Sodio/metabolismo , Tetrodotoxina/farmacología , Animales , Conductividad Eléctrica , Colorantes Fluorescentes , Activación del Canal Iónico , Masculino , Trastornos Migrañosos/tratamiento farmacológico , Trastornos Migrañosos/metabolismo , Neuronas Aferentes/efectos de los fármacos , Técnicas de Placa-Clamp , Ratas Sprague-Dawley , Canales de Sodio/efectos de los fármacosRESUMEN
Many foods and drinks contain histamine; however, the mechanisms that drive histamine taste perception have not yet been investigated. Here, we use a simple model organism, Drosophila melanogaster, to dissect the molecular sensors required to taste histamine. We first investigated histidine and histamine taste perception by performing a binary food choice assay and electrophysiology to identify essential sensilla for histamine sensing in the labellum. Histamine was found to activate S-type sensilla, which harbor bitter-sensing gustatory receptor neurons. Moreover, unbiased genetic screening for chemoreceptors revealed that a gustatory receptor, GR22e and an ionotropic receptor, IR76b are required for histamine sensing. Ectopic expression of GR22e was sufficient to induce a response in I-type sensilla, which normally do not respond to histamine. Taken together, our findings provide new insights into the mechanisms by which insects discriminate between the toxic histamine and beneficial histidine via their taste receptors.
Asunto(s)
Proteínas de Drosophila , Histamina , Histidina , Receptores de Superficie Celular , Receptores Ionotrópicos de Glutamato , Animales , Células Quimiorreceptoras/efectos de los fármacos , Proteínas de Drosophila/efectos de los fármacos , Proteínas de Drosophila/genética , Proteínas de Drosophila/fisiología , Drosophila melanogaster/genética , Drosophila melanogaster/fisiología , Electrofisiología , Histamina/farmacología , Histidina/farmacología , Receptores de Superficie Celular/efectos de los fármacos , Receptores de Superficie Celular/genética , Receptores de Superficie Celular/fisiología , Receptores Ionotrópicos de Glutamato/efectos de los fármacos , Receptores Ionotrópicos de Glutamato/genética , Receptores Ionotrópicos de Glutamato/fisiología , Sensilos/efectos de los fármacos , Sensilos/metabolismo , Canales de Sodio/efectos de los fármacos , Canales de Sodio/genética , Canales de Sodio/fisiología , Gusto/genética , Gusto/fisiologíaRESUMEN
BACKGROUND: SGLT2 (sodium/glucose cotransporter 2) inhibitors exert robust cardioprotective effects against heart failure in patients with diabetes, and there is intense interest to identify the underlying molecular mechanisms that afford this protection. Because the induction of the late component of the cardiac sodium channel current (late-INa) is involved in the etiology of heart failure, we investigated whether these drugs inhibit late-INa. METHODS: Electrophysiological, in silico molecular docking, molecular, calcium imaging, and whole heart perfusion techniques were used to address this question. RESULTS: The SGLT2 inhibitor empagliflozin reduced late-INa in cardiomyocytes from mice with heart failure and in cardiac Nav1.5 sodium channels containing the long QT syndrome 3 mutations R1623Q or ΔKPQ. Empagliflozin, dapagliflozin, and canagliflozin are all potent and selective inhibitors of H2O2-induced late-INa (half maximal inhibitory concentration = 0.79, 0.58, and 1.26 µM, respectively) with little effect on peak sodium current. In mouse cardiomyocytes, empagliflozin reduced the incidence of spontaneous calcium transients induced by the late-INa activator veratridine in a similar manner to tetrodotoxin, ranolazine, and lidocaine. The putative binding sites for empagliflozin within Nav1.5 were investigated by simulations of empagliflozin docking to a three-dimensional homology model of human Nav1.5 and point mutagenic approaches. Our results indicate that empagliflozin binds to Nav1.5 in the same region as local anesthetics and ranolazine. In an acute model of myocardial injury, perfusion of isolated mouse hearts with empagliflozin or tetrodotoxin prevented activation of the cardiac NLRP3 (nuclear-binding domain-like receptor 3) inflammasome and improved functional recovery after ischemia. CONCLUSIONS: Our results provide evidence that late-INa may be an important molecular target in the heart for the SGLT2 inhibitors, contributing to their unexpected cardioprotective effects.
Asunto(s)
Compuestos de Bencidrilo/farmacología , Glucósidos/farmacología , Canales de Sodio/efectos de los fármacos , Inhibidores del Cotransportador de Sodio-Glucosa 2/farmacología , Animales , Compuestos de Bencidrilo/uso terapéutico , Glucósidos/uso terapéutico , Humanos , Masculino , Ratones , Inhibidores del Cotransportador de Sodio-Glucosa 2/uso terapéuticoRESUMEN
Aconitine (ACO), a main active ingredient of Aconitum, is well-known for its cardiotoxicity. However, the mechanisms of toxic action of ACO remain unclear. In the current study, we investigated the cardiac effects of ACO and mesaconitine (MACO), a structurally related analog of ACO identified in Aconitum with undocumented cardiotoxicity in guinea pigs. We showed that intravenous administration of ACO or MACO (25 µg/kg) to guinea pigs caused various types of arrhythmias in electrocardiogram (ECG) recording, including ventricular premature beats (VPB), atrioventricular blockade (AVB), ventricular tachycardia (VT), and ventricular fibrillation (VF). MACO displayed more potent arrhythmogenic effect than ACO. We conducted whole-cell patch-clamp recording in isolated guinea pig ventricular myocytes, and observed that treatment with ACO (0.3, 3 µM) or MACO (0.1, 0.3 µM) depolarized the resting membrane potential (RMP) and reduced the action potential amplitude (APA) and durations (APDs) in a concentration-dependent manner. The ACO- and MACO-induced AP remodeling was largely abolished by an INa blocker tetrodotoxin (2 µM) and partly abolished by a specific Na+/K+ pump (NKP) blocker ouabain (0.1 µM). Furthermore, we observed that treatment with ACO or MACO attenuated NKP current (INa/K) and increased peak INa by accelerating the sodium channel activation with the EC50 of 8.36 ± 1.89 and 1.33 ± 0.16 µM, respectively. Incubation of ventricular myocytes with ACO or MACO concentration-dependently increased intracellular Na+ and Ca2+ concentrations. In conclusion, the current study demonstrates strong arrhythmogenic effects of ACO and MACO resulted from increasing the peak INa via accelerating sodium channel activation and inhibiting the INa/K. These results may help to improve our understanding of cardiotoxic mechanisms of ACO and MACO, and identify potential novel therapeutic targets for Aconitum poisoning.
Asunto(s)
Aconitina/análogos & derivados , Aconitina/toxicidad , Arritmias Cardíacas/inducido químicamente , Cardiotoxicidad/etiología , Aconitina/aislamiento & purificación , Aconitum/química , Potenciales de Acción/efectos de los fármacos , Animales , Arritmias Cardíacas/fisiopatología , Cardiotoxicidad/fisiopatología , Electrocardiografía , Cobayas , Masculino , Potenciales de la Membrana/efectos de los fármacos , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/patología , Técnicas de Placa-Clamp , Canales de Sodio/efectos de los fármacos , Canales de Sodio/metabolismoRESUMEN
BACKGROUND: Concomitant apamin-sensitive small conductance calcium-activated potassium current (IKAS) activation and sodium current inhibition induce J-wave syndrome (JWS) in rabbit hearts. Sudden death in JWS occurs predominantly in men at night when parasympathetic tone is strong. OBJECTIVE: The purpose of this study was to test the hypotheses that acetylcholine (ACh), the parasympathetic transmitter, activates IKAS and causes JWS in the presence of ajmaline. METHODS: We performed optical mapping in Langendorff-perfused rabbit hearts and whole-cell voltage clamp to determine IKAS in isolated ventricular cardiomyocytes. RESULTS: ACh (1 µM) + ajmaline (2 µM) induced J-point elevations in all (6 male and 6 female) hearts from 0.01± 0.01 to 0.31 ± 0.05 mV (P<.001), which were reduced by apamin (specific IKAS inhibitor, 100 nM) to 0.14 ± 0.02 mV (P<.001). More J-point elevation was noted in male than in female hearts (P=.037). Patch clamp studies showed that ACh significantly (P<.001) activated IKAS in isolated male but not in female ventricular myocytes (n=8). Optical mapping studies showed that ACh induced action potential duration (APD) heterogeneity, which was more significant in right than in left ventricles. Apamin in the presence of ACh prolonged both APD at the level of 25% (P<.001) and APD at the level of 80% (P<.001) and attenuated APD heterogeneity. Ajmaline further increased APD heterogeneity induced by ACh. Ventricular arrhythmias were induced in 6 of 6 male and 1 of 6 female hearts (P=.015) in the presence of ACh and ajmaline, which was significantly suppressed by apamin in the former. CONCLUSION: ACh activates ventricular IKAS. ACh and ajmaline induce JWS and facilitate the induction of ventricular arrhythmias more in male than in female ventricles.
Asunto(s)
Acetilcolina/farmacología , Ajmalina/farmacología , Arritmias Cardíacas/tratamiento farmacológico , Ventrículos Cardíacos/metabolismo , Miocitos Cardíacos/metabolismo , Canales de Potasio Calcio-Activados/efectos de los fármacos , Canales de Sodio/metabolismo , Animales , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/patología , Agonistas Colinérgicos/farmacología , Modelos Animales de Enfermedad , Ventrículos Cardíacos/efectos de los fármacos , Ventrículos Cardíacos/patología , Preparación de Corazón Aislado/métodos , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/patología , Imagen Óptica , Técnicas de Placa-Clamp , Canales de Potasio Calcio-Activados/metabolismo , Conejos , Canales de Potasio de Pequeña Conductancia Activados por el Calcio/antagonistas & inhibidores , Canales de Sodio/efectos de los fármacos , Bloqueadores del Canal de Sodio Activado por Voltaje/farmacologíaRESUMEN
Isoliensinine (IL) extracted from lotus seed has a good therapeutic effect on cardiovascular diseases. However, its effect on ion channels of ventricular myocytes is still unclear. We used whole-cell patch-clamp techniques to detect the effects of IL on transmembrane ion currents and action potential (AP) in isolated rabbit left ventricular myocytes. IL inhibited the transient sodium current (INaT), late sodium current (INaL) enlarged by sea anemone toxin (ATX II) and L-type calcium current (ICaL) in a concentration-dependent manner without affecting inward rectifier potassium current (IK1) and delayed rectifier potassium current (IK). These inhibitory effects are mainly manifested as reduced the AP amplitude (APA) and maximum depolarization velocity (Vmax) and shortened the action potential duration (APD), but had no significant effect on the resting membrane potential (RMP). Moreover, IL significantly eliminated ATX II-induced early afterdepolarizations (EADs) and high extracellular calcium-induced delayed afterdepolarizations (DADs). These results revealed that IL effectively eliminated EADs and DADs through inhibiting INaL and ICaL in ventricular myocytes, which indicates it has potential antiarrhythmic action.
Asunto(s)
Potenciales de Acción/efectos de los fármacos , Antiarrítmicos/farmacología , Arritmias Cardíacas/prevención & control , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio Tipo L/efectos de los fármacos , Isoquinolinas/farmacología , Miocitos Cardíacos/efectos de los fármacos , Bloqueadores de los Canales de Sodio/farmacología , Canales de Sodio/efectos de los fármacos , Animales , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/fisiopatología , Canales de Calcio Tipo L/metabolismo , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Masculino , Miocitos Cardíacos/metabolismo , Conejos , Canales de Sodio/metabolismo , Factores de TiempoRESUMEN
BACKGROUND: Delta-opioid receptor (DOR)-mediated modulation of hippocampal neural networks is involved in emotions, cognition, and in pathophysiology and treatment of mood disorders. In this study, we examined the effects of DOR agonist (SNC80) and antagonist (naltrindole) on the excitability of individual hippocampal neurons. METHODS: Primary neuronal cultures were prepared from hippocampi of newborn rats and cultivated in vitro for 8-14 days (DIV8-14). The effects of SNC80 naltrindole on evoked and spontaneous action potentials (APs) were measured at DIV8-9 and DIV13-14, respectively. RESULTS: SNC80 (100 µM) potentiated spontaneous AP firing and stimulated sodium current; naltrindole had opposite effects. The stimulatory effect of 100 µM of SNC80 was revoked by pre-administration of 1 µM of naltrindole. SNC80 and naltrindole induced similar inhibitory effects on the evoked AP firing and on the calcium current. Further, SNC80 inhibited both peak and sustained potassium currents. Naltrindole had no effect on potassium currents. CONCLUSION: We suggest that the effects of naltrindole and high concentration of SNC80 on the sodium currents are mediated via DORs and underlying the changes in spontaneous activity. The inhibitory effects of SNC80 on calcium and potassium currents might also be DOR-dependent; these currents might mediate SNC80 effect on the evoked AP firing. The inhibitory effects of naltrindole on calcium and of low doses of SNC80 on sodium currents might be however DOR independent. The behavioral effects of SNC80 and naltrindole, observed in previous studies, might be mediated, at least in part, via the modulatory effect of these ligands on the excitability of hippocampal neurons.
Asunto(s)
Hipocampo/efectos de los fármacos , Neuronas/efectos de los fármacos , Receptores Opioides delta/efectos de los fármacos , Potenciales de Acción/efectos de los fármacos , Animales , Conducta Animal/efectos de los fármacos , Benzamidas/farmacología , Canales de Calcio/efectos de los fármacos , Femenino , Naltrexona/análogos & derivados , Naltrexona/farmacología , Antagonistas de Narcóticos/farmacología , Piperazinas/farmacología , Canales de Potasio/efectos de los fármacos , Cultivo Primario de Células , Ratas , Ratas Wistar , Receptores Opioides delta/agonistas , Receptores Opioides delta/antagonistas & inhibidores , Canales de Sodio/efectos de los fármacos , Canales de Sodio/metabolismoRESUMEN
BACKGROUND: Although the widely used single L-enantiomers of local anesthetics have less toxic effects on the cardiovascular and central nervous systems, the mechanisms mediating their antinociceptive actions are not well understood. The authors hypothesized that significant differences in the ion channel blocking abilities of the enantiomers of bupivacaine would be identified. METHODS: The authors performed electrophysiologic analysis on rat dorsal root ganglion neurons in vitro and on spinal transmissions in vivo. RESULTS: In the dorsal root ganglion, these anesthetics decreased the amplitudes of action potentials. The half-maximum inhibitory concentrations of D-enantiomer D-bupivacaine were almost equal for Aß (29.5 µM), Aδ (29.7µM), and C (29.8 µM) neurons. However, the half-maximum inhibitory concentrations of L-bupivacaine was lower for Aδ (19.35 µM) and C (19.5 µM) neurons than for A ß (79.4 µM) neurons. Moreover, D-bupivacaine almost equally inhibited tetrodotoxin-resistant (mean ± SD: 15.8 ± 10.9% of the control, n = 14, P < 0.001) and tetrodotoxin-sensitive (15.4 ± 15.6% of the control, n = 11, P = 0.004) sodium currents. In contrast, L-bupivacaine suppressed tetrodotoxin-resistant sodium currents (26.1 ± 19.5% of the control, n = 18, P < 0.001) but not tetrodotoxin-sensitive sodium currents (74.5 ± 18.2% of the control, n = 11, P = 0.477). In the spinal dorsal horn, L-bupivacaine decreased the area of pinch-evoked excitatory postsynaptic currents (39.4 ± 11.3% of the control, n = 7, P < 0.001) but not touch-evoked responses (84.2 ± 14.5% of the control, n = 6, P = 0.826). In contrast, D-bupivacaine equally decreased pinch- and touch-evoked responses (38.8 ± 9.5% of the control, n = 6, P = 0.001, 42.9 ± 11.8% of the control, n = 6, P = 0.013, respectively). CONCLUSIONS: These results suggest that the L-enantiomer of bupivacaine (L-bupivacaine) effectively inhibits noxious transmission to the spinal dorsal horn by blocking action potential conduction through C and Aδ afferent fibers.
Asunto(s)
Anestésicos Locales/farmacología , Bupivacaína/farmacología , Neuronas/efectos de los fármacos , Nocicepción/efectos de los fármacos , Nervios Periféricos/efectos de los fármacos , Células del Asta Posterior/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos , Animales , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Masculino , Fibras Nerviosas Mielínicas/efectos de los fármacos , Fibras Nerviosas Amielínicas/efectos de los fármacos , Técnicas de Placa-Clamp , Ratas , Ratas Sprague-Dawley , Canales de Sodio/efectos de los fármacos , Estereoisomerismo , Tetrodotoxina/farmacologíaRESUMEN
The output from the peripheral terminals of primary nociceptive neurons, which detect and encode the information regarding noxious stimuli, is crucial in determining pain sensation. The nociceptive terminal endings are morphologically complex structures assembled from multiple branches of different geometry, which converge in a variety of forms to create the terminal tree. The output of a single terminal is defined by the properties of the transducer channels producing the generation potentials and voltage-gated channels, translating the generation potentials into action potential (AP) firing. However, in the majority of cases, noxious stimuli activate multiple terminals; thus, the output of the nociceptive neuron is defined by the integration and computation of the inputs of the individual terminals. Here, we used a computational model of nociceptive terminal tree to study how the architecture of the terminal tree affects the input-output relation of the primary nociceptive neurons. We show that the input-output properties of the nociceptive neurons depend on the length, the axial resistance (Ra), and location of individual terminals. Moreover, we show that activation of multiple terminals by a capsaicin-like current allows summation of the responses from individual terminals, thus leading to increased nociceptive output. Stimulation of the terminals in simulated models of inflammatory or neuropathic hyperexcitability led to a change in the temporal pattern of AP firing, emphasizing the role of temporal code in conveying key information about changes in nociceptive output in pathologic conditions, leading to pain hypersensitivity.SIGNIFICANCE STATEMENT Noxious stimuli are detected by terminal endings of primary nociceptive neurons, which are organized into morphologically complex terminal trees. The information from multiple terminals is integrated along the terminal tree, computing the neuronal output, which propagates toward the CNS, thus shaping the pain sensation. Here, we revealed that the structure of the nociceptive terminal tree determines the output of nociceptive neurons. We show that the integration of noxious information depends on the morphology of the terminal trees and how this integration and, consequently, the neuronal output change under pathologic conditions. Our findings help to predict how nociceptive neurons encode noxious stimuli and how this encoding changes in pathologic conditions, leading to pain.
Asunto(s)
Nociceptores/fisiología , Nociceptores/ultraestructura , Nervios Periféricos/fisiología , Nervios Periféricos/ultraestructura , Terminales Presinápticos/fisiología , Terminales Presinápticos/ultraestructura , Células Receptoras Sensoriales/fisiología , Células Receptoras Sensoriales/ultraestructura , Potenciales de Acción/fisiología , Capsaicina/farmacología , Simulación por Computador , Humanos , Modelos Neurológicos , Neuralgia/fisiopatología , Nocicepción , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Canales de Sodio/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiologíaRESUMEN
BACKGROUND: Salt, a common environmental stress factor, inhibits plant growth and reduces yields. Melatonin is a pleiotropic molecule that regulates plant growth and can alleviate environmental stress in plants. All previous research on this topic has focused on the use of melatonin to improve the relatively low salt tolerance of glycophytes by promoting growth and enhancing antioxidant ability. It is unclear whether exogenous melatonin can increase the salt tolerance of halophytes, particularly recretohalophytes, by enhancing salt secretion from the salt glands. RESULTS: To examine the mechanisms of melatonin-mediated salt tolerance, we explored the effects of exogenous applications of melatonin on the secretion of salt from the salt glands of Limonium bicolor (a kind of recretohalophyte) seedlings and on the expression of associated genes. A pretreatment with 5 µM melatonin significantly improved the growth of L. bicolor seedlings under 300 mM NaCl. Furthermore, exogenous melatonin significantly increased the dry weight and endogenous melatonin content of L. bicolor. In addition, this treatment reduced the content of Na+ and Cl- in leaves, but increased the K+ content. Both the salt secretion rate of the salt glands and the expression level of genes encoding ion transporters (LbHTK1, LbSOS1, LbPMA, and LbNHX1) and vesicular transport proteins (LbVAMP721, LbVAP27, and LbVAMP12) were significantly increased by exogenous melatonin treatment. These results indicate that melatonin improves the salt tolerance of the recretohalophyte L. bicolor via the upregulation of salt secretion by the salt glands. CONCLUSIONS: Our results showed that melatonin can upregulate the expression of genes encoding ion transporters and vesicle transport proteins to enhance salt secretion from the salt glands. Combining the results of the current study with previous research, we formulated a novel mechanism by which melatonin increases salt secretion in L. bicolor. Ions in mesophyll cells are transported to the salt glands through ion transporters located at the plasma membrane. After the ions enter the salt glands, they are transported to the collecting chamber adjacent to the secretory pore through vesicle transport and ions transporter and then are secreted from the secretory pore of salt glands, which maintain ionic homeostasis in the cells and alleviate NaCl-induced growth inhibition.
Asunto(s)
Genes de Plantas/efectos de los fármacos , Melatonina/farmacología , Reguladores del Crecimiento de las Plantas/farmacología , Plumbaginaceae/efectos de los fármacos , Canales de Sodio/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Hojas de la Planta/metabolismo , Plumbaginaceae/genética , Plumbaginaceae/crecimiento & desarrollo , Plumbaginaceae/metabolismo , Tolerancia a la Sal/efectos de los fármacos , Tolerancia a la Sal/genética , Canales de Sodio/metabolismo , Regulación hacia ArribaRESUMEN
Conotoxins (CnTX) are bioactive peptides produced by marine molluscs belonging to Conus genus. The biochemical structure of these venomous peptides is characterized by a low number of amino acids linked with disulfide bonds formed by a high degree of post-translational modifications and glycosylation steps which increase the diversity and rate of evolution of these molecules. CnTX different isoforms are known to target ion channels and, in particular, voltage-gated sodium (Na+) channels (Nav channels). These are transmembrane proteins fundamental in excitable cells for generating the depolarization of plasma membrane potential known as action potential which propagates electrical signals in muscles and nerves for physiological functions. Disorders in Nav channel activity have been shown to induce neurological pathologies and pain states. Here, we describe the current knowledge of CnTX isoform modulation of the Nav channel activity, the mechanism of action and the potential therapeutic use of these toxins in counteracting neurological dysfunctions.
Asunto(s)
Conotoxinas/toxicidad , Canales de Sodio/efectos de los fármacos , Animales , Caracol Conus , Activación del Canal Iónico , Canales IónicosRESUMEN
Several experimental studies have recently demonstrated that temporary autonomic block using botulinum toxin (BoNT/A1) might be a novel option for the treatment of atrial fibrillation. However, the assessment of antiarrhythmic properties of BoNT has so far been limited, relying exclusively on vagal stimulation and rapid atrial pacing models. The present study examined the antiarrhythmic effect of specially formulated BoNT/A1-chitosan nanoparticles (BTN) in calcium chloride-, barium chloride- and electrically induced arrhythmia rat models. BTN enhanced the effect of BoNT/A1. Subepicardial injection of BTN resulted in a significant antiarrhythmic effect in investigated rat models. BTN formulation antagonizes arrhythmia induced by the activation of Ca, K and Na channels.
Asunto(s)
Antiarrítmicos/farmacología , Arritmias Cardíacas/prevención & control , Toxinas Botulínicas Tipo A/farmacología , Sistema de Conducción Cardíaco/efectos de los fármacos , Frecuencia Cardíaca/efectos de los fármacos , Nanopartículas , Potenciales de Acción/efectos de los fármacos , Animales , Antiarrítmicos/química , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/fisiopatología , Toxinas Botulínicas Tipo A/química , Canales de Calcio/efectos de los fármacos , Canales de Calcio/metabolismo , Quitosano/química , Modelos Animales de Enfermedad , Composición de Medicamentos , Sistema de Conducción Cardíaco/metabolismo , Sistema de Conducción Cardíaco/fisiopatología , Masculino , Canales de Potasio/efectos de los fármacos , Canales de Potasio/metabolismo , Ratas Wistar , Canales de Sodio/efectos de los fármacos , Canales de Sodio/metabolismoRESUMEN
Existing evidence suggests that the local anaesthetic mexiletine can be beneficial for patients with asthma. However, caution is required since anaesthesia of the airways inhibits protective bronchodilator neuronal reflexes, limiting applications in conditions of hyperirritable airways. Here, we describe the synthesis of a new series of mexiletine analogues, which were screened for reduced activity in Na+ channels and improved smooth muscle relaxant effects, that were evaluated using the patch-clamp technique and an isolated tracheal organ bath, respectively. JME-173 (1-(4-bromo-3,5-dimethylphenoxy)propan-2-amine) was the most effective among the four mexiletine analogues investigated. JME-173 was then studied in vivo using a murine model of lung inflammation induced by cigarette smoke (CS) and in vitro using neutrophil chemotaxis and mast cell degranulation assays. Finally, the JME-173 pharmacokinetic profile was assessed using HPLC-MS/MS bioanalytical method. JME-173 directly inhibited IL-8 (CXCL8)- and FMLP-induced human neutrophil chemotaxis and allergen-induced mast cell degranulation. After oral administration 1 h before CS exposure, JME-173 (50 mg/kg) strongly reduced the increased number of macrophages and neutrophils recovered in the bronchoalveolar effluent without altering lymphocyte counts. Pharmacokinetic experiments of JME-173 (10 mg/kg, orally) showed values of maximum concentration (Cmax), maximum time (Tmax), area under the blood concentration-time curve (AUC0-t) and area under the blood concentration-time curve from 0-Inf (AUC0-inf) of 163.3 ± 38.3 ng/mL, 1.2 ± 0.3 h, 729.4 ± 118.3 ng*h/ml and 868.9 ± 117.1 ng*h/ml (means ± S.E.M.), respectively. Collectively, these findings suggest that JME-173 has the potential to be an effective oral treatment for diseases associated with bronchoconstriction and inflammation.
Asunto(s)
Antiinflamatorios no Esteroideos/farmacología , Mexiletine/análogos & derivados , Mexiletine/farmacología , Parasimpatolíticos/farmacología , Bloqueadores de los Canales de Sodio/farmacología , Canales de Sodio/efectos de los fármacos , Animales , Área Bajo la Curva , Líquido del Lavado Bronquioalveolar/citología , Degranulación de la Célula/efectos de los fármacos , Humanos , Masculino , Mastocitos/efectos de los fármacos , Ratones , Infiltración Neutrófila/efectos de los fármacos , Técnicas de Placa-Clamp , Neumonía/inducido químicamente , Neumonía/tratamiento farmacológico , Ratas , Ratas Wistar , Humo , Relación Estructura-Actividad , Productos de TabacoRESUMEN
BACKGROUND: Long QT syndrome has been associated with sudden cardiac death likely caused by early afterdepolarizations (EADs) and polymorphic ventricular tachycardias (PVTs). Suppressing the late sodium current (INaL) may counterbalance the reduced repolarization reserve in long QT syndrome and prevent EADs and PVTs. METHODS: We tested the effects of the selective INaL blocker GS967 on PVT induction in a transgenic rabbit model of long QT syndrome type 2 using intact heart optical mapping, cellular electrophysiology and confocal Ca2+ imaging, and computer modeling. RESULTS: GS967 reduced ventricular fibrillation induction under a rapid pacing protocol (n=7/14 hearts in control versus 1/14 hearts at 100 nmol/L) without altering action potential duration or restitution and dispersion. GS967 suppressed PVT incidences by reducing Ca2+-mediated EADs and focal activity during isoproterenol perfusion (at 30 nmol/L, n=7/12 and 100 nmol/L n=8/12 hearts without EADs and PVTs). Confocal Ca2+ imaging of long QT syndrome type 2 myocytes revealed that GS967 shortened Ca2+ transient duration via accelerating Na+/Ca2+ exchanger (INCX)-mediated Ca2+ efflux from cytosol, thereby reducing EADs. Computer modeling revealed that INaL potentiates EADs in the long QT syndrome type 2 setting through (1) providing additional depolarizing currents during action potential plateau phase, (2) increasing intracellular Na+ (Nai) that decreases the depolarizing INCX thereby suppressing the action potential plateau and delaying the activation of slowly activating delayed rectifier K+ channels (IKs), suggesting important roles of INaL in regulating Nai. CONCLUSIONS: Selective INaL blockade by GS967 prevents EADs and abolishes PVT in long QT syndrome type 2 rabbits by counterbalancing the reduced repolarization reserve and normalizing Nai. Graphic Abstract: A graphic abstract is available for this article.