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1.
Life Sci ; 255: 117814, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32439300

RESUMO

AIMS: Amiodarone (AMIO) is currently used in medical practice to reverse ventricular tachycardia. Here we determine the effects of AMIO in the electromechanical properties of isolated left ventricle myocyte (LVM) from mice and guinea pig and in a cellular model of Long QT Syndrome Type 3 (LQTS-3) using anemone neurotoxin 2 (ATX II), which induces increase of late sodium current in LVM. MAIN METHODS AND KEY FINDINGS: Using patch-clamp technique, fluorescence imaging to detect cellular Ca2+ transient and sarcomere detection systems we evaluate the effect of AMIO in healthy LVM. AMIO produced a significant reduction in the percentage of sarcomere shortening (0.1, 1 and 10 µM) in a range of pacing frequencies, however, without significant attenuation of Ca2+ transient. Also, 10 µM of AMIO caused the opposite effect on action potential repolarization of mouse and guinea pig LVM. When LVM from mouse and guinea pig were paced in a range of pacing frequencies and exposed to ATX (10 nM), AMIO (10 µM) was only able to abrogate electromechanical arrhythmias in LVM from guinea pig at lower pacing frequency. SIGNIFICANCE: AMIO has negative inotropic effect with opposite effect on action potential waveform in mouse and guinea pig LVM. Furthermore, the antiarrhythmic action of AMIO in LQTS-3 is species and frequency-dependent, which indicates that AMIO may be beneficial for some types of arrhythmias related to late sodium current.


Assuntos
Amiodarona/farmacologia , Antiarrítmicos/farmacologia , Doença do Sistema de Condução Cardíaco/tratamento farmacológico , Síndrome do QT Longo/tratamento farmacológico , Miócitos Cardíacos/efeitos dos fármacos , Amiodarona/administração & dosagem , Animais , Antiarrítmicos/administração & dosagem , Doença do Sistema de Condução Cardíaco/fisiopatologia , Relação Dose-Resposta a Droga , Cobaias , Ventrículos do Coração/citologia , Síndrome do QT Longo/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Miócitos Cardíacos/metabolismo , Técnicas de Patch-Clamp , Sarcômeros/efeitos dos fármacos , Sarcômeros/metabolismo , Canais de Sódio/efeitos dos fármacos , Canais de Sódio/metabolismo , Especificidade da Espécie
2.
Life Sci ; 244: 117333, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31962132

RESUMO

AIMS: Detect the antiarrhythmic effect of crotonoside (Cro). MAIN METHODS: We used whole-cell patch-clamp techniques to detect the effects of Cro on action potentials (APs) and transmembrane ion currents in isolated rabbit left ventricular myocytes. We also verified the effect of Cro on ventricular arrhythmias caused by aconitine in vivo. KEY FINDINGS: Cro reduced the maximum depolarization velocity (Vmax) of APs and shortened the action potential duration (APD) in a concentration-dependent manner, but it had no significant effect on the resting membrane potential (RMP) or action potential amplitude (APA). It also inhibited the peak sodium current (INa) and L-type calcium current (ICaL) in a concentration-dependent manner with half-maximal inhibitory concentrations (IC50) of 192 µmol/L and 159 µmol/L, respectively. However, Cro had no significant effects on the inward rectifier potassium current (IK1) or rapidly activating delayed rectifier potassium current (IKr). Sea anemone toxin II (ATX II) increased the late sodium current (INaL), but Cro abolished this effect. Moreover, Cro significantly abolished ATX II-induced early afterdepolarizations (EADs) and high extracellular Ca2+ concentration (3.6 mmol/L)-induced delayed afterdepolarizations (DADs). We also verified that Cro effectively delayed the onset time and reduced the incidence of ventricular arrhythmias caused by aconitine in vivo. SIGNIFICANCE: These results revealed that Cro effectively inhibits INa, INaL, and ICaL in ventricular myocytes. Cro has antiarrhythmic potential and thus deserves further study.


Assuntos
Guanina/farmacologia , Miócitos Cardíacos/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Animais , Antiarrítmicos/metabolismo , Antiarrítmicos/farmacologia , Arritmias Cardíacas/fisiopatologia , Cálcio/metabolismo , Canais de Cálcio/efeitos dos fármacos , China , Feminino , Guanina/metabolismo , Ventrículos do Coração/metabolismo , Técnicas de Patch-Clamp/métodos , Coelhos , Sódio/metabolismo , Canais de Sódio/efeitos dos fármacos
3.
Cardiovasc J Afr ; 30(5): 268-274, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31361295

RESUMO

INTRODUCTION: Our previous experiments showed that the transient sodium current (INa) was abnormally increased in early ischaemia and atorvastatin could inhibit INa. The aim of this study was to observe the time-dependent effects of simulated ischaemia on INa and characterise the direct effects of atorvastatin on ischaemic INa. METHODS: Left ventricular myocytes were isolated from Wistar rats and randomly divided into two groups: a control group (normal to simulated ischaemia) and a statin group (normal to simulated ischaemia with 5 µmol/l atorvastatin). The INa was recorded under normal conditions (as baseline) by whole-cell patch clamp and recorded from three to 21 minutes in the next phase of simulated ischaemic conditions. RESULTS: In the control group, normalised INa (at -40 mV) was increased to the peak (1.15 ± 0.08 mA) at three minutes of ischaemia compared with baseline (0.95 ± 0.04 mA, p < 0.01), it subsequently returned to baseline levels at nine and 11 minutes of ischaemia (0.98 ± 0.12 and 0.92 ± 0.12 mA, respectively), and persistently decreased with prolonged ischaemic time. In the statin group, there were no differences between baseline and the early stages of ischaemia (0.97 ± 0.04 mA at baseline vs 0.92 ± 0.12 mA in ischaemia for three minutes, p > 0.05). CONCLUSION: Our results suggest that, in the early stages of ischaemia, changes in INa in ventricular myocytes are time-dependent, showing an initial increase followed by a decrease, while atorvastatin inhibited the transient increase in INa and made the change more gradual.


Assuntos
Antiarrítmicos/farmacologia , Arritmias Cardíacas/prevenção & controle , Atorvastatina/farmacologia , Ventrículos do Coração/efeitos dos fármacos , Ativação do Canal Iônico/efeitos dos fármacos , Isquemia Miocárdica/tratamento farmacológico , Miócitos Cardíacos/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Sódio/metabolismo , Animais , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/fisiopatologia , Feminino , Frequência Cardíaca/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Ventrículos do Coração/fisiopatologia , Cinética , Masculino , Potenciais da Membrana , Isquemia Miocárdica/metabolismo , Isquemia Miocárdica/fisiopatologia , Miócitos Cardíacos/metabolismo , Ratos Wistar , Canais de Sódio/metabolismo
4.
J Pharmacol Toxicol Methods ; 100: 106605, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31255744

RESUMO

INTRODUCTION: Cardiac late Na+ current (INaL) contributes to ventricular action potential duration. Pathological increase in INaL is arrhythmogenic, and inhibition of INaL offers protection against ventricular repolarization disturbance. Recently, two INaL datasets generated by different laboratories that assessed current inhibition by a panel of clinical drugs as a part of the Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative were published. The results revealed a surprising degree of data variability despite of the use of a standardized voltage protocol. This study investigated whether remaining procedural differences related to experimental methods and data analysis associated with these datasets can produce differences in INaL pharmacology. METHODS: Whole cell voltage clamp recordings were performed on cells expressing NaV1.5 α- and ß1-subunits to study: 1) the impact of gating modifiers used to augment INaL (ATX-II vs. veratridine), internal solution composition (with vs. without ATP and GTP), and recording temperature (23 °C vs 37 °C) on stability of INaL measured across the duration of a patch clamp experiment; 2) mechanisms of each gating modifier on Na+ channels; and 3) effects of six drugs (lidocaine, mexiletine, chloroquine, ranolazine, ritonavir, and verapamil) on INaL induced by either gating modifier. RESULTS: Stability of INaL is affected by the choice of gating modifier, presence of nucleotides in the internal solution, and recording temperature. ATX-II and veratridine produced different changes in Na+ channel gating, inducing mechanistically distinct INaL. Drug potencies on inhibiting INaL were dependent on the choice of gating modifier and current region where drug effects were measured. DISCUSSION: INaL pharmacology can be impacted by all experimental factors examined in this study. The effect of gating modifier and current region used to quantify drug inhibition alone led to 30× difference in half inhibitory concentration (IC50) for ritonavir, demonstrating that substantial difference in drug inhibition can be produced. Drug potencies on inhibiting INaL derived from different patch clamp studies may thus not be generalizable. For INaL pharmacology to be useful for in silico modeling or interpreting drug-induced changes in cardiac action potentials or ECG, standardizing INaL experimental procedures including data analysis methods is necessary to minimize data variability.


Assuntos
Potenciais de Ação/efeitos dos fármacos , Arritmias Cardíacas/induzido quimicamente , Ventrículos do Coração/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Arritmias Cardíacas/diagnóstico , Simulação por Computador , Ventrículos do Coração/metabolismo , Humanos , Nucleotídeos/metabolismo , Técnicas de Patch-Clamp , Canais de Sódio/metabolismo , Temperatura
5.
Ann Neurol ; 86(4): 626-640, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31340057

RESUMO

OBJECTIVE: Drug-resistant epilepsy causes great clinical danger and still lacks effective treatments. METHODS: Here, we used multifaceted approaches combining electrophysiology, optogenetics, and chemogenetics in a classic phenytoin-resistant epilepsy model to reveal the key target of subicular pyramidal neurons in phenytoin resistance. RESULTS: In vivo neural recording showed that the firing rate of pyramidal neurons in the subiculum, but not other hippocampal subregions, could not be inhibited by phenytoin in phenytoin-resistant rats. Selective inhibition of subicular pyramidal neurons by optogenetics or chemogenetics reversed phenytoin resistance, whereas selective activation of subicular pyramidal neurons induced phenytoin resistance. Moreover, long-term low-frequency stimulation at the subiculum, which is clinically feasible, significantly inhibited the subicular pyramidal neurons and reversed phenytoin resistance. Furthermore, in vitro electrophysiology revealed that off-target use of phenytoin on sodium channels of subicular pyramidal neurons was involved in the phenytoin resistance, and clinical neuroimaging data suggested the volume of the subiculum in drug-resistant patients was related to the usage of sodium channel inhibitors. INTERPRETATION: These results highlight that the subicular pyramidal neurons may be a key switch control of drug-resistant epilepsy and represent a new potential target for precise treatments. ANN NEUROL 2019;86:626-640.


Assuntos
Epilepsia Resistente a Medicamentos/fisiopatologia , Epilepsia do Lobo Temporal/fisiopatologia , Hipocampo/patologia , Células Piramidais/efeitos dos fármacos , Animais , Atrofia/patologia , Clozapina/análogos & derivados , Clozapina/farmacologia , Epilepsia Resistente a Medicamentos/patologia , Estimulação Elétrica/métodos , Epilepsia do Lobo Temporal/patologia , Feminino , Humanos , Masculino , Inibição Neural/fisiologia , Optogenética , Fenitoína/farmacologia , Ratos , Bloqueadores dos Canais de Sódio/efeitos adversos , Canais de Sódio/efeitos dos fármacos
6.
Anesthesiology ; 131(1): 94-104, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31166240

RESUMO

BACKGROUND: Volatile anesthetics inhibit presynaptic voltage-gated sodium channels to reduce neurotransmitter release, but their effects on excitatory neuron excitability by sodium current inhibition are unclear. The authors hypothesized that inhibition of transient and persistent neuronal sodium currents by the volatile anesthetic isoflurane contributes to reduced hippocampal pyramidal neuron excitability. METHODS: Whole-cell patch-clamp recordings of sodium currents of hippocampal cornu ammonis pyramidal neurons were performed in acute mouse brain slices. The actions of isoflurane on both transient and persistent sodium currents were analyzed at clinically relevant concentrations of isoflurane. RESULTS: The median inhibitory concentration of isoflurane for inhibition of transient sodium currents was 1.0 ± 0.3 mM (~3.7 minimum alveolar concentration [MAC]) from a physiologic holding potential of -70 mV. Currents from a hyperpolarized holding potential of -120 mV were minimally inhibited (median inhibitory concentration = 3.6 ± 0.7 mM, ~13.3 MAC). Isoflurane (0.55 mM; ~2 MAC) shifted the voltage-dependence of steady-state inactivation by -6.5 ± 1.0 mV (n = 11, P < 0.0001), but did not affect the voltage-dependence of activation. Isoflurane increased the time constant for sodium channel recovery from 7.5 ± 0.6 to 12.7 ± 1.3 ms (n = 13, P < 0.001). Isoflurane also reduced persistent sodium current density (median inhibitory concentration = 0.4 ± 0.1 mM, ~1.5 MAC) and resurgent currents. Isoflurane (0.55 mM; ~2 MAC) reduced action potential amplitude, and hyperpolarized resting membrane potential from -54.6 ± 2.3 to -58.7 ± 2.1 mV (n = 16, P = 0.001). CONCLUSIONS: Isoflurane at clinically relevant concentrations inhibits both transient and persistent sodium currents in hippocampal cornu ammonis pyramidal neurons. These mechanisms may contribute to reductions in both hippocampal neuron excitability and synaptic neurotransmission.


Assuntos
Anestésicos Inalatórios/farmacologia , Hipocampo/efeitos dos fármacos , Isoflurano/farmacologia , Células Piramidais/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Potenciais de Ação , Animais , Feminino , Masculino , Camundongos , Modelos Animais
7.
Circ Arrhythm Electrophysiol ; 12(7): e007294, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31248280

RESUMO

BACKGROUND: Phthalates are used as plasticizers in the manufacturing of flexible, plastic medical products. Patients can be subjected to high phthalate exposure through contact with plastic medical devices. We aimed to investigate the cardiac safety and biocompatibility of mono-2-ethylhexyl phthalate (MEHP), a phthalate with documented exposure in intensive care patients. METHODS: Optical mapping of transmembrane voltage and pacing studies were performed on isolated, Langendorff-perfused rat hearts to assess cardiac electrophysiology after MEHP exposure compared with controls. MEHP dose was chosen based on reported blood concentrations after an exchange transfusion procedure. RESULTS: Thirty-minute exposure to MEHP increased the atrioventricular node (147 versus 107 ms) and ventricular (117 versus 77.5 ms) effective refractory periods, compared with controls. Optical mapping revealed prolonged action potential duration at slower pacing cycle lengths, akin to reverse use dependence. The plateau phase of the action potential duration restitution curve steepened and became monophasic in MEHP-exposed hearts (0.18 versus 0.06 slope). Action potential duration lengthening occurred during late-phase repolarization resulting in triangulation (70.3 versus 56.6 ms). MEHP exposure also slowed epicardial conduction velocity (35 versus 60 cm/s), which may be partly explained by inhibition of Nav1.5 (874 and 231 µmol/L half-maximal inhibitory concentration, fast and late sodium current). CONCLUSIONS: This study highlights the impact of acute MEHP exposure, using a clinically relevant dose, on cardiac electrophysiology in the intact heart. Heightened clinical exposure to plasticized medical products may have cardiac safety implications-given that action potential triangulation and electrical restitution modifications are a risk factor for early after depolarizations and cardiac arrhythmias.


Assuntos
Potenciais de Ação/efeitos dos fármacos , Arritmias Cardíacas/induzido quimicamente , Dietilexilftalato/análogos & derivados , Equipamentos e Provisões/efeitos adversos , Sistema de Condução Cardíaco/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Plastificantes/toxicidade , Animais , Arritmias Cardíacas/diagnóstico , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/fisiopatologia , Simulação por Computador , Dietilexilftalato/toxicidade , Desenho de Equipamento , Sistema de Condução Cardíaco/metabolismo , Sistema de Condução Cardíaco/fisiopatologia , Humanos , Preparação de Coração Isolado , Masculino , Modelos Cardiovasculares , Ratos Sprague-Dawley , Período Refratário Eletrofisiológico/efeitos dos fármacos , Medição de Risco , Canais de Sódio/efeitos dos fármacos , Canais de Sódio/metabolismo , Fatores de Tempo , Imagens com Corantes Sensíveis à Voltagem
8.
J Neuroimmunol ; 332: 198-211, 2019 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-31077855

RESUMO

Excitation of dorsal root ganglion (DRG) neurons by interleukin 1ß (IL-1ß) is implicated in the onset of neuropathic pain. To understand its mechanism of action, isolectin B4 positive (IB4+) DRG neurons were exposed to 100pM IL-1ß for 5-6d. A reversible increase in action potential (AP) amplitude reflected increased TTX-sensitive sodium current (TTX-S INa). An irreversible increase in AP duration reflected decreased Ca2+- sensitive K+ conductance (BK(Ca) channels). Different processes thus underlie regulation of the two channel types. Since changes in AP shape facilitated Ca2+ influx, this explains how IL-1ß facilitates synaptic transmission in the dorsal horn; thereby provoking pain.


Assuntos
Canais de Cálcio/efeitos dos fármacos , Gânglios Espinais/citologia , Interleucina-1beta/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Neuralgia/etiologia , Canais de Potássio/efeitos dos fármacos , Células Receptoras Sensoriais/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Animais , Canais de Cálcio/metabolismo , Tamanho Celular , Fator Neurotrófico Derivado de Linhagem de Célula Glial/farmacologia , Masculino , Fator de Crescimento Neural/farmacologia , Neuralgia/metabolismo , Técnicas de Patch-Clamp , Peptídeos/farmacologia , Lectinas de Plantas/análise , Canais de Potássio/metabolismo , Ratos , Ratos Sprague-Dawley , Células Receptoras Sensoriais/metabolismo , Células Receptoras Sensoriais/ultraestrutura , Canais de Sódio/metabolismo
9.
Neuron ; 102(4): 801-812.e5, 2019 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-30926280

RESUMO

Nociceptive terminals possess the elements for detecting, transmitting, and modulating noxious signals, thus being pivotal for pain sensation. Despite this, a functional description of the transduction process by the terminals, in physiological conditions, has not been fully achieved. Here, we studied how nociceptive terminals in vivo convert noxious stimuli into propagating signals. By monitoring noxious-stimulus-induced Ca2+ dynamics from mouse corneal terminals, we found that initiation of Na+ channel (Nav)-dependent propagating signals takes place away from the terminal and that the starting point for Nav-mediated propagation depends on Nav functional availability. Acute treatment with the proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1ß (IL-1ß) resulted in a shift of the location of Nav involvement toward the terminal, thus increasing nociceptive excitability. Moreover, a shift of Nav involvement toward the terminal occurs in corneal hyperalgesia resulting from acute photokeratitis. This dynamic change in the location of Nav-mediated propagation initiation could underlie pathological pain hypersensitivity.


Assuntos
Potenciais de Ação , Córnea/inervação , Hiperalgesia/metabolismo , Nociceptores/metabolismo , Terminações Pré-Sinápticas/metabolismo , Canais de Sódio/metabolismo , Animais , Canais de Cálcio/metabolismo , Sinalização do Cálcio , Lesões da Córnea , Interleucina-1beta/farmacologia , Camundongos , Plasticidade Neuronal , Terminações Pré-Sinápticas/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Canais de Cátion TRPV/metabolismo , Fator de Necrose Tumoral alfa/farmacologia , Raios Ultravioleta
10.
J Neurol Surg A Cent Eur Neurosurg ; 80(2): 72-80, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30381811

RESUMO

BACKGROUND: Electrocardiogram (ECG) changes in patients with subarachnoid hemorrhage (SAH) are frequent. ST- and/or T-wave changes in ECG seem to predominate. STUDY AIMS: To investigate the ion channel mechanisms of SAH-induced ventricular excitation-contraction coupling changes and the possible protective effect of N-acetylcysteine (NAC). METHODS: Three groups of rabbits were used for the experiments. In two groups, SAH was induced by replacing the cerebrospinal fluid (CSF) with fresh autologous blood. In the control group, CSF was replaced with isotonic saline. In one SAH group, NAC was administered daily beginning at SAH induction. On day 5, ventricular action potentials, ionic currents, contractions, and intracellular free ion concentrations were recorded from the myocytes. RESULTS: In the SAH group, no change was found in the sodium currents, but the transient outward potassium currents were depressed, rapid repolarizing currents were increased, and t-type calcium currents were increased. Contractions and the intracellular free calcium concentration were depressed. NAC treatment, in contrast, not only restores these electrical remodeling changes but also the contractile abnormalities in the cardiac myocytes. CONCLUSION: The changes in the action potential duration can be attributed to the measured ionic current changes. However, the exact mechanism, other than the oxidative stress, by which the NAC treatment protects the cardiac muscle needs additional investigations.


Assuntos
Acetilcisteína/uso terapêutico , Potenciais de Ação/efeitos dos fármacos , Depuradores de Radicais Livres/uso terapêutico , Ventrículos do Coração/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Hemorragia Subaracnóidea/fisiopatologia , Animais , Canais de Cálcio/efeitos dos fármacos , Modelos Animais de Doenças , Ventrículos do Coração/patologia , Masculino , Coelhos , Canais de Sódio/efeitos dos fármacos
11.
eNeuro ; 5(4)2018.
Artigo em Inglês | MEDLINE | ID: mdl-30225345

RESUMO

Action potentials propagating along axons are often followed by prolonged afterdepolarization (ADP) lasting for several tens of milliseconds. Axonal ADP is thought to be an important factor in modulating the fidelity of spike propagation during repetitive firings. However, the mechanism as well as the functional significance of axonal ADP remain unclear, partly due to inaccessibility to small structures of axon for direct electrophysiological recordings. Here, we examined the ionic and electrical mechanisms underlying axonal ADP using whole-bouton recording from mossy fiber terminals in mice hippocampal slices. ADP following axonal action potentials was strongly enhanced by focal application of veratridine, an inhibitor of Na+ channel inactivation. In contrast, tetrodotoxin (TTX) partly suppressed ADP, suggesting that a Na+ channel-dependent component is involved in axonal ADP. The remaining TTX-resistant Na+ channel-independent component represents slow capacitive discharge reflecting the shape and electrical properties of the axonal membrane. We also addressed the functional impact of axonal ADP on presynaptic function. In paired-pulse stimuli, we found that axonal ADP minimally affected the peak height of subsequent action potentials, although the rising phase of action potentials was slightly slowed, possibly due to steady-state inactivation of Na+ channels by prolonged depolarization. Voltage clamp analysis of Ca2+ current elicited by action potential waveform commands revealed that axonal ADP assists short-term facilitation of Ca2+ entry into the presynaptic terminals. Taken together, these data show that axonal ADP maintains reliable firing during repetitive stimuli and plays important roles in the fine-tuning of short-term plasticity of transmitter release by modulating Ca2+ entry into presynaptic terminals.


Assuntos
Potenciais de Ação/fisiologia , Sinalização do Cálcio/fisiologia , Moduladores de Transporte de Membrana/farmacologia , Fibras Musgosas Hipocampais/fisiologia , Canais de Sódio/efeitos dos fármacos , Veratridina/farmacologia , Potenciais de Ação/efeitos dos fármacos , Animais , Sinalização do Cálcio/efeitos dos fármacos , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fibras Musgosas Hipocampais/efeitos dos fármacos
12.
Cardiovasc Drugs Ther ; 32(5): 413-425, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30173392

RESUMO

PURPOSE: Mechanical stretch increases sodium and calcium entry into myocytes and activates the late sodium current. GS967, a triazolopyridine derivative, is a sodium channel blocker with preferential effects on the late sodium current. The present study evaluates whether GS967 inhibits or modulates the arrhythmogenic electrophysiological effects of myocardial stretch. METHODS: Atrial and ventricular refractoriness and ventricular fibrillation modifications induced by acute stretch were studied in Langendorff-perfused rabbit hearts (n = 28) using epicardial multiple electrodes and high-resolution mapping techniques under control conditions and during the perfusion of GS967 at different concentrations (0.03, 0.1, and 0.3 µM). RESULTS: On comparing ventricular refractoriness, conduction velocity and wavelength obtained before stretch had no significant changes under each GS967 concentration while atrial refractoriness increased under GS967 0.3 µM. Under GS967, the stretch-induced changes were attenuated, and no significant differences were observed between before and during stretch. GS967 0.3 µM diminished the normal stretch-induced changes resulting in longer (less shortened) atrial refractoriness (138 ± 26 ms vs 95 ± 9 ms; p < 0.01), ventricular refractoriness (155 ± 18 ms vs 124 ± 16 ms; p < 0.01) and increments in spectral concentration (23 ± 5% vs 17 ± 2%; p < 0.01), the fifth percentile of ventricular activation intervals (46 ± 8 ms vs 31 ± 3 ms; p < 0.05), and wavelength of ventricular fibrillation (2.5 ±0.5 cm vs 1.7 ± 0.3 cm; p < 0.05) during stretch. The stretch-induced increments in dominant frequency during ventricular fibrillation (control = 38%, 0.03 µM = 33%, 0.1 µM = 33%, 0.3 µM = 14%; p < 0.01) and the stretch-induced increments in arrhythmia complexity index (control = 62%, 0.03µM = 41%, 0.1 µM = 32%, 0.3 µM = 16%; p < 0.05) progressively decreased on increasing the GS967 concentration. CONCLUSIONS: GS967 attenuates stretch-induced changes in cardiac electrophysiology.


Assuntos
Potenciais de Ação/efeitos dos fármacos , Antiarrítmicos/farmacologia , Fibrilação Atrial/prevenção & controle , Mecanorreceptores/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Piridinas/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/efeitos dos fármacos , Triazóis/farmacologia , Fibrilação Ventricular/prevenção & controle , Animais , Fibrilação Atrial/metabolismo , Fibrilação Atrial/fisiopatologia , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Preparação de Coração Isolado , Masculino , Mecanorreceptores/metabolismo , Mecanotransdução Celular/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Coelhos , Período Refratário Eletrofisiológico , Canais de Sódio/metabolismo , Fatores de Tempo , Fibrilação Ventricular/metabolismo , Fibrilação Ventricular/fisiopatologia
13.
Eur J Pharmacol ; 838: 69-77, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30194938

RESUMO

Migraine is characterized by recurrent and disabling headaches; therefore, several drugs have been widely prescribed to prevent acute migraine attacks. Amitriptyline, a tricyclic antidepressant, is among the most commonly administered. It is poorly known, however, whether amitriptyline modulates the excitability of dural afferent neurons that transmit pain signals from the dura mater. In this study, the effects of amitriptyline on tetrodotoxin-resistant (TTX-R) Na+ channels were examined in acutely isolated rat dural afferent neurons, which were identified by the fluorescent dye DiI. The TTX-R Na+ currents (INa) were recorded from medium-sized DiI-positive neurons using a whole-cell patch clamp technique. Amitriptyline (3 µM) slightly reduced the peak component of transient INa and induced a marked decrease in the steady-state component of transient TTX-R INa, as well as in the slow ramp-induced TTX-R INa. Our findings suggest that amitriptyline specifically inhibits persistent Na+ currents mediated by TTX-R Na+ channels. While amitriptyline had minor effects on voltage-activation/inactivation, it increased the extent of the use-dependent inhibition of TTX-R Na+ channels. Amitriptyline also affected the inactivation kinetics of TTX-R Na+ channels by significantly accelerating the inactivation of TTX-R Na+ channels and slowing the subsequent recovery. Amitriptyline decreased the number of action potentials by increasing the threshold for their generation. In conclusion, the amitriptyline-mediated diverse modulation of TTX-R Na+ channels would be, at least in part, responsible for its prophylactic efficacy for migraine attacks.


Assuntos
Amitriptilina/farmacologia , Antidepressivos Tricíclicos/farmacologia , Transtornos de Enxaqueca/tratamento farmacológico , Nociceptores/efeitos dos fármacos , Canais de Sódio/efeitos dos fármacos , Amitriptilina/uso terapêutico , Animais , Antidepressivos Tricíclicos/uso terapêutico , Dura-Máter/citologia , Dura-Máter/metabolismo , Masculino , Potenciais da Membrana/efeitos dos fármacos , Transtornos de Enxaqueca/patologia , Nociceptores/metabolismo , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-Dawley , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/metabolismo , Tetrodotoxina/farmacologia
14.
Toxicol Appl Pharmacol ; 356: 182-190, 2018 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-30125596

RESUMO

Taurine-magnesium coordination compound (TMCC) exhibits antiarrhythmic effects in cesium-chloride-and ouabain-induced arrhythmias; however, the mechanism underlying these effects on arrhythmia remains poorly understood. Here, we investigated the effects of TMCC on aconitine-induced arrhythmia in vivo and the electrophysiological effects of this compound in rat ventricular myocytes in vitro. Aconitine was used to induce arrhythmias in rats, and the dosages required to produce ventricular premature contraction (VPC), ventricular tachycardia (VT), ventricular fibrillation (VF), and cardiac arrest (CA) were recorded. Additionally, the sodium current (INa) and L-type calcium current (ICa,L) were analyzed in normal and aconitine-treated ventricular myocytes using whole-cell patch-clamp recording. In vivo, intravenous administration of TMCC produced marked antiarrhythmic effects, as indicated by the increased dose of aconitine required to induce VPC, VT, VF, and CA. Moreover, this effect was abolished by administration of sodium channel opener veratridine and calcium channel agonist Bay K8644. In vitro, TMCC inhibited aconitine-induced increases in INa and ICa,L. These results revealed that TMCC inhibited aconitine-induced arrhythmias through effects on INa and ICa,L.


Assuntos
Aconitina , Antiarrítmicos/uso terapêutico , Arritmias Cardíacas/induzido quimicamente , Arritmias Cardíacas/tratamento farmacológico , Canais Iônicos/efeitos dos fármacos , Compostos de Magnésio/uso terapêutico , Taurina/uso terapêutico , Animais , Canais de Cálcio Tipo L/efeitos dos fármacos , Fenômenos Eletrofisiológicos/efeitos dos fármacos , Feminino , Parada Cardíaca/induzido quimicamente , Parada Cardíaca/prevenção & controle , Ventrículos do Coração/citologia , Ventrículos do Coração/efeitos dos fármacos , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Técnicas de Patch-Clamp , Ratos , Ratos Wistar , Canais de Sódio/efeitos dos fármacos
15.
Biomed Pharmacother ; 106: 510-522, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29990839

RESUMO

BACKGROUND: RSD921, the R,R enantiomer of the kappa (k) agonist PD117,302, lacks significant activity on opioid receptors. METHODS: The pharmacological and toxicological actions were studied with reference to cardiovascular, cardiac, antiarrhythmic, toxic and local anaesthetic activity. RESULTS: In rats, dogs and baboons, RSD921 dose-dependently reduced blood pressure and heart rate. In a manner consistent with sodium channel blockade it prolonged the PR and QRS intervals of the ECG. Furthermore, in rats and NHP, RSD921 increased the threshold currents for induction of extra-systoles and ventricular fibrillation (VFt), and prolonged effective refractory period (ERP). In rats, RSD921 was protective against arrhythmias induced by electrical stimulation and coronary artery occlusion. Application of RSD921 to voltage-clamped rat cardiac myocytes blocked sodium currents. RSD921 also blocked transient (ito) and sustained (IKsus) outward potassium currents, albeit with reduced potency relative to sodium current blockade. Sodium channel blockade due to RSD921 in myocytes and isolated hearts was enhanced under ischaemic conditions (low pH and high extracellular potassium concentration). When tested on the cardiac, neuronal and skeletal muscle forms of sodium channels expressed in Xenopus laevis oocytes, RSD921 produced equipotent tonic block of sodium currents, enhanced channel block at reduced pH (6.4) and marked use-dependent block of the cardiac isoform. RSD921 had limited but quantifiable effects in subacute toxicology studies in rats and dogs. Pharmacokinetic analyses were performed in baboons. Plasma concentrations producing cardiac actions in vivo after intravenous administration of RSD921 were similar to the concentrations effective in the in vitro assays utilized. CONCLUSIONS: RSD921 primarily blocks sodium currents, and possesses antiarrhythmic and local anaesthetic activity.


Assuntos
Anestésicos Locais/farmacologia , Antiarrítmicos/farmacologia , Arritmias Cardíacas/prevenção & controle , Frequência Cardíaca/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Pirróis/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/efeitos dos fármacos , Tiofenos/farmacologia , Potenciais de Ação , Administração Intravenosa , Anestésicos Locais/administração & dosagem , Anestésicos Locais/farmacocinética , Anestésicos Locais/toxicidade , Animais , Antiarrítmicos/administração & dosagem , Antiarrítmicos/farmacocinética , Antiarrítmicos/toxicidade , Anti-Hipertensivos/farmacologia , Arritmias Cardíacas/etiologia , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/fisiopatologia , Pressão Sanguínea/efeitos dos fármacos , Modelos Animais de Doenças , Cães , Relação Dose-Resposta a Droga , Feminino , Cobaias , Humanos , Injeções Intradérmicas , Preparação de Coração Isolado , Masculino , Camundongos , Miócitos Cardíacos/metabolismo , Condução Nervosa/efeitos dos fármacos , Limiar da Dor/efeitos dos fármacos , Papio , Ratos , Ratos Sprague-Dawley , Bloqueadores dos Canais de Sódio/administração & dosagem , Bloqueadores dos Canais de Sódio/farmacocinética , Bloqueadores dos Canais de Sódio/toxicidade , Canais de Sódio/metabolismo , Fatores de Tempo , Xenopus laevis
16.
J Gen Physiol ; 150(9): 1317-1331, 2018 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-30018039

RESUMO

Voltage-gated sodium (NaV) channels are important targets of general anesthetics, including the intravenous anesthetic propofol. Electrophysiology studies on the prokaryotic NaV channel NaChBac have demonstrated that propofol promotes channel activation and accelerates activation-coupled inactivation, but the molecular mechanisms of these effects are unclear. Here, guided by computational docking and molecular dynamics simulations, we predict several propofol-binding sites in NaChBac. We then strategically place small fluorinated probes at these putative binding sites and experimentally quantify the interaction strengths with a fluorinated propofol analogue, 4-fluoropropofol. In vitro and in vivo measurements show that 4-fluoropropofol and propofol have similar effects on NaChBac function and nearly identical anesthetizing effects on tadpole mobility. Using quantitative analysis by 19F-NMR saturation transfer difference spectroscopy, we reveal strong intermolecular cross-relaxation rate constants between 4-fluoropropofol and four different regions of NaChBac, including the activation gate and selectivity filter in the pore, the voltage sensing domain, and the S4-S5 linker. Unlike volatile anesthetics, 4-fluoropropofol does not bind to the extracellular interface of the pore domain. Collectively, our results show that propofol inhibits NaChBac at multiple sites, likely with distinct modes of action. This study provides a molecular basis for understanding the net inhibitory action of propofol on NaV channels.


Assuntos
Proteínas de Bactérias/efeitos dos fármacos , Hipnóticos e Sedativos/farmacologia , Propofol/farmacologia , Canais de Sódio/efeitos dos fármacos , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Flúor , Células HEK293 , Humanos , Larva , Espectroscopia de Ressonância Magnética , Técnicas de Patch-Clamp , Canais de Sódio/genética , Canais de Sódio/metabolismo , Xenopus laevis
17.
J Gen Physiol ; 150(9): 1299-1316, 2018 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-30018038

RESUMO

Propofol is widely used in the clinic for the induction and maintenance of general anesthesia. As with most general anesthetics, however, our understanding of its mechanism of action remains incomplete. Local and general anesthetics largely inhibit voltage-gated Na+ channels (Navs) by inducing an apparent stabilization of the inactivated state, associated in some instances with pore block. To determine the biophysical and molecular basis of propofol action in Navs, we investigated NaChBac and NavMs, two prokaryotic Navs with distinct voltage dependencies and gating kinetics, by whole-cell patch clamp electrophysiology in the absence and presence of propofol at clinically relevant concentrations (2-10 µM). In both Navs, propofol induced a hyperpolarizing shift of the pre-pulse inactivation curve without any significant effects on recovery from inactivation at strongly hyperpolarized voltages, demonstrating that propofol does not stabilize the inactivated state. Moreover, there was no evidence of fast or slow pore block by propofol in a non-inactivating NaChBac mutant (T220A). Propofol also induced hyperpolarizing shifts of the conductance-voltage relationships with negligible effects on the time constants of deactivation at hyperpolarized voltages, indicating that propofol does not stabilize the open state. Instead, propofol decreases the time constants of macroscopic activation and inactivation. Adopting a kinetic scheme of Nav gating that assumes preferential closed-state recovery from inactivation, a 1.7-fold acceleration of the rate constant of activation and a 1.4-fold acceleration of the rate constant of inactivation were sufficient to reproduce experimental observations with computer simulations. In addition, molecular dynamics simulations and molecular docking suggest that propofol binding involves interactions with gating machinery in the S4-S5 linker and external pore regions. Our findings show that propofol is primarily a positive gating modulator of prokaryotic Navs, which ultimately inhibits the channels by promoting activation-coupled inactivation.


Assuntos
Proteínas de Bactérias/efeitos dos fármacos , Hipnóticos e Sedativos/farmacologia , Propofol/farmacologia , Canais de Sódio/efeitos dos fármacos , Canais de Sódio Disparados por Voltagem/efeitos dos fármacos , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Células HEK293 , Humanos , Cinética , Mutação , Técnicas de Patch-Clamp , Canais de Sódio/genética , Canais de Sódio/metabolismo , Canais de Sódio Disparados por Voltagem/metabolismo
18.
Pharmacol Ther ; 188: 176-185, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29605457

RESUMO

The complex process of pain control commonly involves the use of systemic analgesics; however, in many cases, a more potent and effective polypharmacological approach is needed to promote clinically significant improvement. Additionally, considering side effects caused by current painkillers, drug discovery is once more turning to nature as a source of more efficient therapeutic alternatives. In this context, arthropod venoms contain a vast array of bioactive substances that have evolved to selectively bind to specific pharmacological targets involved in the pain signaling pathway, playing an important role as pain activators or modulators, the latter serving as promising analgesic agents. The current review explores how the pain pathway works and surveys neuroactive compounds obtained from arthropods' toxins, which function as pain modulators through their interaction with specific ion channels and membrane receptors, emerging as promising candidates for drug design and development.


Assuntos
Analgésicos/farmacologia , Venenos de Artrópodes/farmacologia , Animais , Canais de Cálcio/efeitos dos fármacos , Canais de Cálcio/fisiologia , Humanos , Dor/fisiopatologia , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Canais de Sódio/efeitos dos fármacos , Canais de Sódio/fisiologia , Canais de Cátion TRPV/efeitos dos fármacos , Canais de Cátion TRPV/fisiologia
19.
Life Sci ; 196: 48-55, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29307525

RESUMO

AIMS: The sperm plasma membrane contains specific ion channels and transporters that initiate changes in Ca2+, Na+, K+ and H+ ions in the sperm cytoplasm. Ion channels are key regulators of the sperm membrane potential, cytoplasmic Ca2+ and intracellular pH (pHi), which leads to regulate motility, capacitation, acrosome reaction and other physiological processes crucial for successful fertilization. Expression of epithelial sodium channels (ENaC) and voltage-gated sodium channels (Nav) in human spermatozoa has been reported, but the role of Na+ fluxes sodium channels in the regulation of sperm cell function remains poorly understood. In this context, we aimed to analyze the physiological role of Nav channels in human sperm. MAIN METHODS: Motility and hyperactivation analysis was conducted by CASA analysis. Flow cytometry and spectrophotometry approaches were carried out to measure Capacitation, Acrosome reaction, immunohistochemistry for Tyr-residues phosporylation, [Ca2+]i levels and membrane potential. KEY FINDINGS: Functional studies showed that veratridine, a voltage-gated sodium channel activator, increased sperm progressive motility without producing hyperactivation while the Nav antagonist lidocaine did induce hyperactivated motility. Veratridine increased protein tyrosine phosphorylation, an event occurring during capacitation, and its effects were inhibited in the presence of lidocaine and tetrodotoxin. Veratridine had no effect on the acrosome reaction by itself, but was able to block the progesterone-induced acrosome reaction. Moreover, veratridine caused a membrane depolarization and modified the effect of progesterone on [Ca2+]i and sperm membrane potential. SIGNIFICANCE: Our results suggest that veratridine-sensitive Nav channels are involved on human sperm fertility acquisition regulating motility, capacitation and the progesterone-induced acrosome reaction in human sperm.


Assuntos
Fertilização/efeitos dos fármacos , Agonistas de Canais de Sódio/farmacologia , Canais de Sódio/efeitos dos fármacos , Espermatozoides/efeitos dos fármacos , Veratridina/farmacologia , Reação Acrossômica/efeitos dos fármacos , Adolescente , Adulto , Feminino , Humanos , Imuno-Histoquímica , Técnicas In Vitro , Lidocaína/farmacologia , Masculino , Potenciais da Membrana/efeitos dos fármacos , Progesterona/antagonistas & inibidores , Progesterona/farmacologia , Receptores Androgênicos/efeitos dos fármacos , Sêmen/efeitos dos fármacos , Sódio/metabolismo , Bloqueadores dos Canais de Sódio/farmacologia , Capacitação Espermática/efeitos dos fármacos , Motilidade Espermática/efeitos dos fármacos , Adulto Jovem
20.
Toxicon ; 143: 51-58, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29337221

RESUMO

The soluble venom from the scorpion Tityus metuendus was characterized by various methods. In vivo experiments with mice showed that it is lethal. Extended electrophysiological recordings using seven sub-types of human voltage gated sodium channels (hNav1.1 to 1.7) showed that it contains both α- and ß-scorpion toxin types. Fingerprint analysis by mass spectrometry identified over 200 distinct molecular mass components. At least 60 sub-fractions were recovered from HPLC separation. Five purified peptides were sequenced by Edman degradation, and their complete primary structures were determined. Additionally, three other peptides have had their N-terminal amino acid sequences determined by Edman degradation and reported. Mass spectrometry analysis of tryptic digestion of the soluble venom permitted the identification of the amino acid sequence of 111 different peptides. Search for similarities of the sequences found indicated that they probably are: sodium and potassium channel toxins, metalloproteinases, hyaluronidases, endothelin and angiotensin-converting enzymes, bradykinin-potentiating peptide, hypothetical proteins, allergens, other enzymes, other proteins and peptides.


Assuntos
Venenos de Escorpião/química , Venenos de Escorpião/toxicidade , Escorpiões , Sequência de Aminoácidos , Animais , Células CHO , Cricetulus , Feminino , Células HEK293 , Humanos , Masculino , Camundongos , Peptídeos/química , Proteoma , Bloqueadores dos Canais de Sódio , Canais de Sódio/efeitos dos fármacos
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