RESUMEN
To clarify the pharmacological properties of the Na+/Ca2+ exchanger (NCX) inhibitor SEA0400 as an antiarrhythmic agent, we assessed its effects on rapid component of delayed rectifier K+ current (IKr) blocker-induced torsade de pointes (TdP) in isoflurane-anesthetized rabbits. Atrioventricular block was induced in rabbits using a catheter ablation technique, and the monophasic action potential (MAP) of the right ventricle was measured under electrical pacing at 60 beats/min. In non-treated control animals, intravenous administration of low-dose (0.3 mg/kg) or high-dose nifekalant (3 mg/kg) prolonged the MAP duration (MAP90) by 113 ± 11 ms (n = 5) and 237 ± 39 ms (n = 5), respectively, where TdP was induced in 1/5 animals treated with a low dose and in 3/5 animals treated with a high dose of nifekalant. In SEA0400-treated animals, low- and high-dose nifekalant prolonged the MAP90 by 65 ± 13 ms (n = 5) and 230 ± 20 ms (n = 5), respectively. No TdP was induced by the low dose but 1/5 animals treated with a high dose of nifekalant developed TdP. In verapamil-treated animals, low-dose and high-dose nifekalant prolonged MAP90 by 50 ± 12 ms (n = 5) and 147 ± 30 ms (n = 5), respectively, without inducing TdP. These results suggest that SEA0400 has the potential to inhibit low-dose nifekalant-induced TdP by suppressing the MAP-prolonging action of nifekalant, whereas the drug inhibited high-dose nifekalant-induced TdP without affecting the MAP-prolonging action of nifekalant. This may reveal that, in contrast to verapamil, the antiarrhythmic effects of SEA0400 on IKr blocker-induced TdP may be multifaceted, depending on the severity of the proarrhythmogenic conditions present.
Asunto(s)
Bloqueo Atrioventricular , Síndrome de QT Prolongado , Torsades de Pointes , Animales , Conejos , Bloqueo Atrioventricular/inducido químicamente , Bloqueo Atrioventricular/tratamiento farmacológico , Intercambiador de Sodio-Calcio , Antiarrítmicos/efectos adversos , Síndrome de QT Prolongado/inducido químicamente , Torsades de Pointes/inducido químicamente , Torsades de Pointes/tratamiento farmacológico , Verapamilo/efectos adversos , Potenciales de AcciónRESUMEN
A structure-activity relationship study of 6-unsubstituted-1,4-dihydropyridine and 2,6-unsubstituted-1,4-dihydropyridine derivatives was conducted in an attempt to discover N-type calcium channel blockers that were highly selective over L-type calcium channel blockers. Among the tested compounds, (+)-4-(3,5-dichloro-4-methoxy-phenyl)-1,4-dihydro-pyridine-3,5-dicarboxylic acid 3-cinnamyl ester was found to be an effective and selective N-type calcium channel blocker with oral analgesic potential.
Asunto(s)
Analgésicos/química , Bloqueadores de los Canales de Calcio/química , Canales de Calcio Tipo N/química , Ácidos Carboxílicos/química , Dihidropiridinas/química , Administración Oral , Analgésicos/síntesis química , Analgésicos/farmacología , Animales , Bloqueadores de los Canales de Calcio/síntesis química , Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio Tipo N/metabolismo , Ácidos Carboxílicos/síntesis química , Ácidos Carboxílicos/farmacología , Evaluación Preclínica de Medicamentos , Formaldehído/toxicidad , Dimensión del Dolor/efectos de los fármacos , Ratas , Relación Estructura-ActividadRESUMEN
The effects of K(+)-channel blockers on the action potential duration of the myocardium were examined in isolated right ventricles from the 7 - 10-day-old, 11 - 13-day-old, and 14 - 20-day-old embryo and 1 - 7-day-old hatched chicks. E-4031 significantly prolonged action potential duration at all developmental stages examined; the prolongation was largest in the 11 - 13-day-old embryo and was accompanied by early after-depolarizations. Chromanol 293B showed smaller prolongation at all stages examined. Terfenadine prolonged action potential duration in the 11 - 13-day-old embryo, but not in other stages. Thus, the chick ventricular myocardium changes its repolarization properties during development.
Asunto(s)
Potenciales de Acción/efectos de los fármacos , Canales de Potasio de Tipo Rectificador Tardío/antagonistas & inhibidores , Ventrículos Cardíacos/efectos de los fármacos , Miocardio/metabolismo , Bloqueadores de los Canales de Potasio/farmacología , Canales de Potasio/metabolismo , Animales , Arritmias Cardíacas/inducido químicamente , Arritmias Cardíacas/fisiopatología , Embrión de Pollo , Canales de Potasio de Tipo Rectificador Tardío/metabolismo , Evaluación Preclínica de Medicamentos , Síndrome de QT Prolongado/inducido químicamente , Síndrome de QT Prolongado/fisiopatologíaRESUMEN
Azelnidipine is a new dihydropyridine Ca(2+) channel blocker with long plasma half-life. To understand the in vivo cardiovascular profile of azelnidipine, it was assessed in the halothane-anaesthetized, closed-chest canine model and compared with the effect of amlodipine. We administered azelnidipine in doses of 10, 20 and 70 microg/kg, i.v. or amlodipine in doses of 30, 70 and 200 microg/kg, i.v. cumulatively to the animals. The hypotensive effects of azelnidipine and amlodipine were slow in onset and long-lasted, while their extents of dose-related hypotensive effects were similar. Azelnidipine hardly affected the heart rate or plasma noradrenaline concentration at any doses, whereas the high dose of amlodipine increased these parameters. Azelnidipine as well as amlodipine tended to increase the ventricular contraction, which did not achieve statistical significance. During autonomic receptor blockade with atropine and propranolol, neither drug affected the heart rate, ventricular contraction or plasma noradrenaline concentration, although a more significant hypotensive action was observed. These results indicate that azelnidipine and amlodipine do not directly affect cardiac function. Amlodipine may induce sinus tachycardia via reflex-mediated increase in sympathetic tone. Such lack of reflex tachycardia with azelnidipine will provide potential therapeutic strategy for treatment of patients with cardiovascular diseases, being more beneficial than amlodipine.
Asunto(s)
Amlodipino/farmacología , Ácido Azetidinocarboxílico/análogos & derivados , Bloqueadores de los Canales de Calcio/farmacología , Dihidropiridinas/farmacología , Amlodipino/administración & dosificación , Anestésicos por Inhalación/administración & dosificación , Animales , Ácido Azetidinocarboxílico/administración & dosificación , Ácido Azetidinocarboxílico/farmacología , Bloqueadores de los Canales de Calcio/administración & dosificación , Dihidropiridinas/administración & dosificación , Perros , Relación Dosis-Respuesta a Droga , Femenino , Halotano/administración & dosificación , Frecuencia Cardíaca/efectos de los fármacos , Ventrículos Cardíacos/efectos de los fármacos , Infusiones Intravenosas , Masculino , Contracción Miocárdica/efectos de los fármacos , Norepinefrina/sangreRESUMEN
The utility of corrected and uncorrected QT interval changes for assessing net repolarization delay by I(Kr) (a rapid component of delayed rectifier K(+) currents) blockers was assessed in halothane-anesthetized dogs using the electrocardiogram and monophasic action potential (MAP) recordings with electrical ventricular pacing. Intravenous administration of dl-sotalol (0.2 - 2 mg/kg) prolonged the MAP duration and RR interval, while terfenadine (3 mg/kg) increased the MAP duration but transiently shortened RR interval. The order of correlation coefficient between the MAP duration at a pacing cycle length of 400 ms and MAP duration itself or that with arithmetical correction was uncorrected > Van de Water = Matsunaga > Fridericia > Bazett. These results suggest that Matsunaga's and Van de Water's formulae would better predict the net repolarization delay in the in vivo canine model. Also, the risk of drug candidates that may prolong the QT interval should be judged by change in uncorrected QT interval as well as corrected QT interval.
Asunto(s)
Algoritmos , Canales de Potasio de Tipo Rectificador Tardío/antagonistas & inhibidores , Sistema de Conducción Cardíaco/efectos de los fármacos , Bloqueadores de los Canales de Potasio/farmacología , Función Ventricular/efectos de los fármacos , Potenciales de Acción/efectos de los fármacos , Animales , Presión Sanguínea/efectos de los fármacos , Canales de Potasio de Tipo Rectificador Tardío/metabolismo , Perros , Evaluación Preclínica de Medicamentos/métodos , Electrocardiografía , Frecuencia Cardíaca/efectos de los fármacos , Modelos Lineales , Síndrome de QT Prolongado/inducido químicamente , Bloqueadores de los Canales de Potasio/toxicidad , Valor Predictivo de las Pruebas , Medición de Riesgo , Sotalol/farmacología , Terfenadina/farmacología , Factores de TiempoRESUMEN
Antiallergic drug cyproheptadine (Cyp) is known to have inhibitory activities for L-type calcium channels in addition to histamine and serotonin receptors. Since we found that Cyp had an inhibitory activity against N-type calcium channel, Cyp was optimized to obtain more selective N-type calcium channel blocker with analgesic action. As a consequence of the optimization, we found 13 with potent N-type calcium channel inhibitory activity which had lower inhibitory activities against L-type calcium channel, histamine (H1), and serotonin (5-HT2A) receptors than those of Cyp. 13 showed an oral analgesic activity in rat formalin-induced pain model.
Asunto(s)
Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio Tipo N/efectos de los fármacos , Ciproheptadina/análogos & derivados , Ciproheptadina/farmacología , Diseño de Fármacos , Administración Oral , Animales , Conducta Animal/efectos de los fármacos , Bloqueadores de los Canales de Calcio/síntesis química , Bloqueadores de los Canales de Calcio/química , Línea Celular Tumoral , Ciproheptadina/química , Evaluación Preclínica de Medicamentos , Formaldehído/química , Cobayas , Humanos , Técnicas In Vitro , Masculino , Estructura Molecular , Dolor/inducido químicamente , Dimensión del Dolor/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Receptores Histamínicos/efectos de los fármacos , Receptores de Serotonina/efectos de los fármacos , Estereoisomerismo , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
Potential utility of halothane-anesthetized guinea pigs for detecting drug-induced repolarization delay was analyzed in comparison with urethane-anesthesia (n = 4 for both groups). Basal QT interval was significantly greater under halothane-anesthesia than urethane-anesthesia (192 +/- 7 vs 132 +/- 5 ms, respectively), whereas the reverse was true for the heart rate (190 +/- 7 vs 248 +/- 11 beats/min, respectively). The typical I(Kr)-blocker dl-sotalol (0.1 to 3 mg/kg, i.v.) induced dose-related bradycardia and QT interval prolongation under each anesthesia. The extent of maximum prolongation in the QT interval was greater under halothane-anesthesia than urethane-anesthesia (+101 +/- 15 vs +49 +/- 3 ms, respectively), whereas that of peak change in the heart rate was smaller under the former than the latter (-49 +/- 8 vs -63 +/- 5 beats/min, respectively). Pretreatment of the animals under urethane-anesthesia with the selective I(Ks) blocker chromanol 293B (n = 6) increased the extent of the dl-sotalol-induced QT interval prolongation to +57 +/- 8 ms, which was only 0.56 times of that under the halothane-anesthesia, whereas the pretreatment increased the peak change in the heart rate to -76 +/- 12 ms. These results indicate that the halothane-anesthesia may effectively sensitize the guinea-pig heart to pharmacological I(Kr) blockade.
Asunto(s)
Anestésicos por Inhalación/farmacología , Anestésicos Intravenosos/farmacología , Canales de Potasio de Tipo Rectificador Tardío/antagonistas & inhibidores , Halotano/farmacología , Uretano/farmacología , Potenciales de Acción/efectos de los fármacos , Anestésicos por Inhalación/administración & dosificación , Anestésicos Intravenosos/administración & dosificación , Animales , Cromanos/farmacología , Canales de Potasio de Tipo Rectificador Tardío/metabolismo , Evaluación Preclínica de Medicamentos , Electrocardiografía , Cobayas , Halotano/administración & dosificación , Frecuencia Cardíaca/efectos de los fármacos , Masculino , Potasio/metabolismo , Bloqueadores de los Canales de Potasio/farmacología , Sotalol/farmacología , Sulfonamidas/farmacología , Factores de Tiempo , Uretano/administración & dosificaciónRESUMEN
The utility of halothane-anaesthetized guinea-pigs as an in vivo model for predicting the clinical potential of a drug to induce QT interval prolongation was assessed using the electrocardiogram and monophasic action potential (MAP) recordings with electrical ventricular pacing. Intravenous administration of D-sotalol (0.3 mg kg(-1)) and terfenadine (0.3 mg kg(-1)), blockers of a rapid component of delayed rectifier potassium currents, prolonged the QT interval by 32+/-7 and 23+/-6 ms, respectively, whereas chromanol 293B (1 mg kg(-1)), a blocker of a slow component of delayed rectifier potassium currents, lengthened it by 33+/-8 ms. The extent of the QT interval prolongation by these drugs was greater than those in previous reports using pentobarbital-anaesthetized guinea-pigs. The MAP duration at the control was shortened by decreasing the pacing cycle length from 400 to 200 ms, but the MAP duration at each cycle length was prolonged by D-sotalol. The formulas of Van de Water, Matsunaga, Fridericia and Bazett showed good correlation of the repolarization period when compared with the MAP duration at a pacing cycle length of 400 ms. The halothane-anaesthetized guinea-pig model may possess enough sensitivity to detect drug-induced QT interval prolongation, indicating that halothane anaesthesia can reduce the repolarization reserve of the heart in vivo.
Asunto(s)
Anestésicos por Inhalación/farmacología , Efectos Colaterales y Reacciones Adversas Relacionados con Medicamentos , Halotano/farmacología , Sistema de Conducción Cardíaco/efectos de los fármacos , Ventrículos Cardíacos/efectos de los fármacos , Corazón/efectos de los fármacos , Síndrome de QT Prolongado/inducido químicamente , Potenciales de Acción/efectos de los fármacos , Antagonistas Adrenérgicos beta/administración & dosificación , Antagonistas Adrenérgicos beta/efectos adversos , Algoritmos , Anestésicos por Inhalación/administración & dosificación , Animales , Cromanos/administración & dosificación , Cromanos/farmacología , Canales de Potasio de Tipo Rectificador Tardío/efectos de los fármacos , Evaluación Preclínica de Medicamentos/métodos , Electrocardiografía/efectos de los fármacos , Cobayas , Halotano/administración & dosificación , Antagonistas de los Receptores Histamínicos H1/administración & dosificación , Antagonistas de los Receptores Histamínicos H1/efectos adversos , Modelos Lineales , Masculino , Modelos Animales , Preparaciones Farmacéuticas/administración & dosificación , Bloqueadores de los Canales de Potasio/administración & dosificación , Bloqueadores de los Canales de Potasio/farmacología , Reproducibilidad de los Resultados , Sotalol/administración & dosificación , Sotalol/efectos adversos , Sulfonamidas/administración & dosificación , Sulfonamidas/farmacología , Terfenadina/administración & dosificación , Terfenadina/efectos adversos , Factores de TiempoRESUMEN
Electropharmacological effect of the antipsychotic and antiemetic drug prochlorperazine was assessed using the halothane-anesthetized in vivo canine model (n = 5). Up to 10 times higher than the clinically relevant doses of prochlorperazine (< or = 3 mg/kg, i.v.) did not induce cardiohemodynamic collapse in the model. Meanwhile, clinically relevant to supratherapeutic doses (0.3 - 3 mg/kg, i.v.) prolonged the ventricular repolarization period in a dose-related and reverse-use dependent manner that could become proarrhythmic substrates. Thus, caution has to be paid on the use of prochlorperazine particularly for patients with risks of the elevated plasma drug concentration, compromised cardiac repolarization, and/or frequent ventricular premature beats.
Asunto(s)
Ventrículos Cardíacos/efectos de los fármacos , Proclorperazina/farmacología , Función Ventricular , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Antieméticos/efectos adversos , Antieméticos/farmacología , Antieméticos/uso terapéutico , Antipsicóticos/efectos adversos , Antipsicóticos/farmacología , Antipsicóticos/uso terapéutico , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Fascículo Atrioventricular/efectos de los fármacos , Fascículo Atrioventricular/fisiología , Gasto Cardíaco/efectos de los fármacos , Gasto Cardíaco/fisiología , Estimulación Cardíaca Artificial/métodos , Modelos Animales de Enfermedad , Perros , Relación Dosis-Respuesta a Droga , Evaluación Preclínica de Medicamentos/métodos , Electrocardiografía/métodos , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Frecuencia Cardíaca/fisiología , Infusiones Intravenosas , Masculino , Proclorperazina/efectos adversos , Proclorperazina/uso terapéutico , Periodo Refractario Electrofisiológico/efectos de los fármacos , Periodo Refractario Electrofisiológico/fisiología , Resistencia Vascular/efectos de los fármacos , Resistencia Vascular/fisiología , Función Ventricular Izquierda/efectos de los fármacos , Función Ventricular Izquierda/fisiología , Presión Ventricular/efectos de los fármacos , Presión Ventricular/fisiologíaRESUMEN
While aldosterone receptor blockers improve survival of patients with congestive heart failure, spironolactone and its derivatives were recently shown to block ether-a-go-go-related gene (HERG) channels and native IKs and IKr currents in guinea pig ventricular myocytes. In this study, we examined in vivo electropharmacological effects of an active derivative of spironolactone, potassium canrenoate, using a halothane-anesthetized canine model. Potassium canrenoate was intravenously administered in three doses of 1, 10, and 100 mg/kg per 10 min with a pause of 20 min between doses (n = 5). The low dose hardly affected any of the cardiovascular parameters. The middle dose, a clinically recommended daily maximum i.v. dose, slightly inhibited the intraventricular conduction. The high dose decreased the heart rate, ventricular contraction and blood pressure, delayed the atrioventricular and intraventricular conduction, and prolonged the ventricular repolarization and refractory period. Increment in the refractoriness by the high dose was greater than that in the repolarization, resulting in the reduction of ventricular electrical vulnerability. This unique electrophysiological profile of potassium canrenoate may in part contribute to the favorable clinical results, whereas caution has to be paid on the cardiohemodynamic actions, particularly for patients with risk of elevated plasma drug concentration.
Asunto(s)
Ácido Canrenoico/farmacología , Corazón/efectos de los fármacos , Antagonistas de Receptores de Mineralocorticoides/farmacología , Potenciales de Acción/efectos de los fármacos , Anestesia , Animales , Presión Sanguínea/efectos de los fármacos , Ácido Canrenoico/sangre , Perros , Electrocardiografía/efectos de los fármacos , Femenino , Halotano/farmacología , Corazón/fisiología , Frecuencia Cardíaca/efectos de los fármacos , Masculino , Periodo Refractario Electrofisiológico/efectos de los fármacosRESUMEN
Delayed afterdepolarization (DAD)-induced triggered activity has been considered to be one of the generation mechanisms of ventricular arrhythmias in the presence of intracellular Ca2+ overload. In this study, we analyzed the antiarrhythmic effects of class I antiarrhythmic drugs, namely, disopyramide, procainamide, mexiletine, and flecainide, on a recently developed DAD-induced triggered arrhythmia model, which consists of a canine ventricular septum preparation cross-circulated with a blood-donor dog. After intravenous administration of ouabain to the donor dog, triggered arrhythmias were consistently induced in the cross-circulated preparation by train stimulation (cycle length: 300 ms; train number: 15). Intracoronary administration of disopyramide, procainamide, mexiletine, and flecainide as well as lidocaine suppressed the triggered arrhythmias at clinically relevant doses. Similar doses have been demonstrated to suppress intraventricular conduction in the same experimental model. These results suggest that the Na+ channel inhibition by class I drugs is an effective pharmacological intervention for suppressing Ca2+ overload, which may provide a rationale for the short-term use of class I drugs against the triggered arrhythmias in clinical practice.
Asunto(s)
Antiarrítmicos/farmacología , Técnicas Electrofisiológicas Cardíacas , Corazón/efectos de los fármacos , Animales , Complejos Cardíacos Prematuros/fisiopatología , Perros , Electrocardiografía , Femenino , Corazón/fisiopatología , Sistema de Conducción Cardíaco/efectos de los fármacos , Sistema de Conducción Cardíaco/fisiopatología , Lidocaína , Masculino , Ouabaína , Canales de Sodio/efectos de los fármacosRESUMEN
Given a lack of information, we assessed the effects of Kampo medicines: Dai-saiko-to, Tsu-do-san, San'o-shashin-to, and Sairei-to, which have been used for various gastrointestinal diseases, on the phosphodiesterase activity and smooth muscle tone of the gastrointestinal tract. Clinically relevant concentrations of each Kampo extract (0.1 - 1 mg/ml) decreased the phosphodiesterase activity as well as smooth muscle tone. The extent of phosphodiesterase inhibition as well as smooth muscle relaxation by these Kampo extracts was prominent for the lower gastrointestinal tract. Also, there was a good correlation between the extents of drug-induced phosphodiesterase inhibition and smooth muscle relaxation, indicating the presence of their causal link. These results may partially provide the basis for understanding the mechanism of the clinical utility of Kampo extracts in gastrointestinal tract diseases.
Asunto(s)
Medicamentos Herbarios Chinos/farmacología , Tracto Gastrointestinal/efectos de los fármacos , Tracto Gastrointestinal/enzimología , Medicina Kampo , Relajación Muscular/efectos de los fármacos , Músculo Liso/enzimología , Inhibidores de Fosfodiesterasa/farmacología , Animales , Relación Dosis-Respuesta a Droga , Femenino , Técnicas In Vitro , Relajación Muscular/fisiología , Músculo Liso/efectos de los fármacos , Hidrolasas Diéster Fosfóricas/metabolismo , Ratas , Ratas Sprague-DawleyRESUMEN
Chronotropic, inotropic and coronary vasodilator actions of the clinically available ampoule preparation of Salvia miltiorrhiza/Dalbergia odorifera mixture were examined using canine isolated, blood-perfused heart preparations. The mixture slightly decreased the sinoatrial rate and significantly increased coronary blood flow, but hardly affected the developed tension of the papillary muscle. The effect on coronary blood flow was induced by at least a 10-fold smaller dose than that which induced the chronotropic effect. These results were quite similar to those of a typical calcium channel blocker, verapamil, used in a previous study, suggesting that the Salvia miltiorrhiza/Dalbergia odorifera mixture may have potential as an anti-anginal drug.
Asunto(s)
Medicina Tradicional China , Contracción Miocárdica/efectos de los fármacos , Isquemia Miocárdica/tratamiento farmacológico , Fitoterapia , Extractos Vegetales/uso terapéutico , Rosaceae , Vasodilatadores/farmacología , Animales , China , Perros , Corazón/efectos de los fármacos , Humanos , Infusiones Intravenosas , Extractos Vegetales/administración & dosificación , Extractos Vegetales/farmacologíaRESUMEN
Cardiac effects of 10 kinds of clinically available Kampo medicines were investigated: Kakkon-to (TJ-1), Dai-saiko-to (TJ-8), Boi-ogi-to (TJ-20), Chorei-to (TJ-40), Rokumi-gan (TJ-87), Tsu-do-san (TJ-105), Gosha-jinki-gan (TJ-107), San'o-shashin-to (TJ-113), Sairei-to (TJ-114) and Inchin-gorei-san (TJ-117). Chronotropic and inotropic effects were studied using canine isolated, blood-perfused heart preparations, while subcellular mechanisms were analyzed by measuring the drug-induced changes of the adenylate cyclase activity in the canine ventricular membrane preparation. Intracoronary injections of TJ-1, TJ-20, TJ-105 and TJ-113 increased the sinoatrial rate and developed tension of papillary muscle in a dose-related manner, which was significantly attenuated by the pretreatment of the preparations with beta-blocker propranolol. Meanwhile, the other extracts hardly affected these parameters. TJ-1, TJ-20 and TJ-113 increased the adenylate cyclase activity in a dose-related manner, but their potency was significantly less compared with that by an equivalent concentration of isoproterenol. Moreover, TJ-105 did not increase the adenylate cyclase activity. These results suggest that the positive chronotropic and inotropic effects of TJ-1, TJ-20, TJ- 105 and TJ-113 may be exerted through the direct stimulation of the beta-adrenoceptor and/or the norepinephrine release from the postganglionic nerve terminals in the heart.