Eficácia e segurança da Fampridina comparada com placebo no tratamento de disfunções motoras em adultos portadores de esclerose múltipla: revisão rápida de evidências / Effectiveness and safety of Fampridine compared with placebo in the treatment of motor dysfunctions in adults with multiple sclerosis: quick evidence review

Tecnologia: Fampridina Indicação: Tratamento de disfunções motoras em pacientes portado-res de esclerose múltipla. Pergunta: A Fampridina é eficaz e segurança para o tratamento de disfunções motoras em adultos portadores de esclerose múltipla comparada ao placebo? Méto-dos: Levantamento bibliográfico foi realizado na base de dados PUBMED, seguindo estratégias de buscas predefinidas. Foi feita avaliação da qualidade metodológica das revisões sistemáticas com a ferramenta AMSTAR-2 (Assessing the Methodological Quality of Systematic Reviews Version 2). Resultados: Foram selecionados três estudos que atenderam aos critérios de inclu-são. Conclusão: A fampridina foi eficaz e segura para tratar disfunções motoras em dosagens específicas. Conforme os resultados dos estudos analisados, a fampridina pode melhora de modo significativo e contínuo a capacidade de deambular dos portadores EM. Além disso, pode ser eficaz para tratar habilidades manuais e cognitiva

Technology: Fampridine. Indication: Treatment of motor disorders in patients with multiple sclerosis. Question: Is Fampridine effective and safe for the treatment of multiple sclerosis in adults with functional limitations compared to placebo? Methods: A bibliographic survey was carried out in the PUBMED database, following predefined search strategies. The methodological quality of systematic reviews was evaluated using the Assessing the Methodological Quality of Systematic Reviews Version 2 tool. Results: Three studies that met the inclusion criteria were selected. Conclusion: Fampridine was effective and safe to treat motor disorders at specific dosages. According to the results of the analyzed studies, fampridine can significantly and continuously improve the ability to walk in MS patients. Also, it can be effective for treating manual and cognitive skills

Echinacoside, an active constituent of Herba Cistanche, suppresses epileptiform activity in hippocampal CA3 pyramidal neurons

Echinacoside, an active compound in the herb Herba Cistanche, has been reported to inhibit glutamate release. In this study, we investigated the effects of echinacoside on spontaneous excitatory synaptic transmission changes induced by 4-aminopyridine (4-AP), by using the in vitro rat hippocampal slice technique and whole-cell patch clamp recordings from CA3 pyramidal neurons. Perfusion with echinacoside significantly suppressed the 4-AP-induced epileptiform activity in a concentration-dependent manner. Echinacoside reduced 4-AP-induced increase in frequency of spontaneous excitatory postsynaptic currents (sEPSCs) but it did not affect the amplitude of sEPSCs or glutamate-activated currents, implicating a presynaptic mechanism of action. Echinacoside also potently blocked sustained repetitive firing, which is a basic mechanism of antiepileptic drugs. These results suggest that echinacoside exerts an antiepileptic effect on hippocampal CA3 pyramidal neurons by simultaneously decreasing glutamate release and blocking abnormal firing synchronization. Accordingly, our study provides experimental evidence that echinacoside may represent an effective pharmacological agent for treating epilepsy.

The Effect of Alcohol Administration on the Corpus Cavernosum

PURPOSE: We studied the effects of alcohol administration on the corpus cavernosum (CC) using an animal model. MATERIALS AND METHODS: CC sections and the aortic ring of rabbits were used in an organ bath study. After acute alcohol administration, changes in blood alcohol concentration and electrical stimulation induced intracavernosal pressure/mean arterial pressure (ICP/MAP) percentage were compared in rats. Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) levels in the CC were measured using immunoassays. After chronic alcohol administration, ICP/MAP percentage, cAMP and cGMP were compared in rats. Histological changes were examined using the Masson trichrome stain and the Sircol collagen assay. Endothelial nitric oxide synthase (eNOS) expression was examined using immunohistochemistry and Western blotting. RESULTS: Alcohol relaxed the CC in a dose-dependent manner, and the relaxation response was suppressed when pretreated with propranolol, indomethacin, glibenclamide, and 4-aminopyridine. In rats with acute alcohol exposure, the cAMP level in the CC was significantly greater than was observed in the control group (p<0.05). In rats with chronic alcohol exposure, however, changes in cAMP and cGMP levels were insignificant, and the CC showed markedly smaller areas of smooth muscle, greater amounts of dense collagen (p<0.05). Immunohistochemical analysis of eNOS showed a less intense response, and western blotting showed that eNOS expression was significantly lower in this group (p<0.05). CONCLUSIONS: Acute alcohol administration activated the cAMP pathway with positive effects on erectile function. In contrast, chronic alcohol administration changed the ultrastructures of the CC and suppressed eNOS expression, thereby leading to erectile dysfunction.

Taurine relaxes human radial artery through potassium channel opening action

The vascular actions and mechanisms of taurine were investigated in the isolated human radial artery (RA). RA rings were suspended in isolated organ baths and tension was recorded isometrically. First, a precontraction was achieved by adding potassium chloride (KCl, 45 mM) or serotonin (5-hydroxytryptamine, 5-HT, 30 µM) to organ baths. When the precontractions were stable, taurine (20, 40, 80 mM) was added cumulatively. Antagonistic effect of taurine on calcium chloride (10 µM to 10 mM)-induced contractions was investigated. Taurine-induced relaxations were also tested in the presence of the K⁺ channel inhibitors tetraethylammonium (1 mM), glibenclamide (10 µM) and 4-aminopyridine (1 mM). Taurine did not affect the basal tone but inhibited the contraction induced by 5-HT and KCl. Calcium chloride-induced contractions were significantly inhibited in the presence of taurine (20, 40, 80 mM) (p<0.05). The relaxation to taurine was inhibited by tetraethylammonium (p<0.05). However, glibenclamide and 4-aminopyridine did not affect taurine-induced relaxations. Present experiments show that taurine inhibits 5-HT and KCl-induced contractions in RA, and suggest that large conductance Ca²⁺-activated K⁺ channels may be involved in taurine-induced relaxation of RA.

Intracellular calcium-dependent regulation of the sperm-specific calcium-activated potassium channel, hSlo3, by the BK(Ca) activator LDD175

Plasma membrane hyperpolarization associated with activation of Ca²⁺-activated K⁺ channels plays an important role in sperm capacitation during fertilization. Although Slo3 (slowpoke homologue 3), together with the auxiliary γ2-subunit, LRRC52 (leucine-rich-repeat–containing 52), is known to mediate the pH-sensitive, sperm-specific K⁺ current KSper in mice, the molecular identity of this channel in human sperm remains controversial. In this study, we tested the classical BK(Ca) activators, NS1619 and LDD175, on human Slo3, heterologously expressed in HEK293 cells together with its functional interacting γ2 subunit, hLRRC52. As previously reported, Slo3 K⁺ current was unaffected by iberiotoxin or 4-aminopyridine, but was inhibited by ~50% by 20 mM TEA. Extracellular alkalinization potentiated hSlo3 K⁺ current, and internal alkalinization and Ca²⁺ elevation induced a leftward shift its activation voltage. NS1619, which acts intracellularly to modulate hSlo1 gating, attenuated hSlo3 K⁺ currents, whereas LDD175 increased this current and induced membrane potential hyperpolarization. LDD175-induced potentiation was not associated with a change in the half-activation voltage at different intracellular pHs (pH 7.3 and pH 8.0) in the absence of intracellular Ca²⁺. In contrast, elevation of intracellular Ca²⁺ dramatically enhanced the LDD175-induced leftward shift in the half-activation potential of hSlo3. Therefore, the mechanism of action does not involve pH-dependent modulation of hSlo3 gating; instead, LDD175 may modulate Ca²⁺-dependent activation of hSlo3. Thus, LDD175 potentially activates native KSper and may induce membrane hyperpolarization-associated hyperactivation in human sperm.

Informe de evaluación científica basada en la evidencia disponible: esclerosis múltiple / Scientific evaluation report based on available evidence: multiple sclerosis

INTRODUCCIÓN: La Esclerosis Múltiple (EM) suele presentarse en cerca del 80% de los casos a través de episodios recurrentes y remitentes, los cuales con el tiempo podrán desarrollar a una forma progresiva y persistente. Un 10 a 15% de los casos, evidencia un cuadro sin remisiones desde su inicio. Durante el año 2010, se incorporó bajo modalidad Garantía Explícita en Salud la Esclerosis Múltiple Remitente Recurrente (EMRR), garantizando en su tratamiento fármacos inmunomoduladores de primera línea, Interferones intramusculares, subcutáneos y el Acetato de Glatiramer. Además, cuentan con cobertura a través de la Ley Ricarte Soto desde el año 2015 aquellos pacientes refractarios a la terapia habitual. TECNOLOGÍAS SANITARIAS ANALIZADAS: Alemtuzumab, Ocrelizumab, Fampridina, Teriflunomida, Dimetilfumarato. EFICACIA DE LOS TRATAMIENTOS: Se extrajo la evidencia de 2 revisiones sistemáticas que reportan 3 Ensayos Controlados Aleatorizados (ECA) para teriflunomida y dimetilfumarato. Adicionalmente, se incluyó información de 1 y 5 ECAs para el tratamiento de alemtuzumab y ocrelizumab, respectivamente. Teriflunomida logra un mayor número de pacientes con ausencia de brotes a los 12 meses. En cuanto a la progresión de la discapacidad asociada a la enfermedad, teriflunomida probablemente no es mejor que placebo para disminuir el número de pacientes libres de progresión de la discapacidad a 2 años. Alemtuzumab probablemente logra un menor número de pacientes con brotes a los 2 años, en comparación a Interferón B, mientras que los pacientes que reciben dimetilfumarato tienen una menor probabilidad de tener brotes que los pacientes tratados con placebo. Ocrelizumab para la Esclerosis Múltiple Primaria Progresiva (EMPP), se compara contra placebo y no se encuentran efectos relevantes en la mayor parte de outcomes (pacientes con confirmación de progresión, SF-36), salvo en indicadores específicos como el número de lesiones activas en T2 ó el volumen cerebral. Para pacientes con EMRR al compararse con Interferón beta-1, se evidencia una reducción de la progresión confirmada a la semana 12, 24 y 96, y reduce la tasa anualizada de brotes a la semana 96. Finalmente, en pacientes con EMRR al comparar ocrelizumab versus placebo, éste podría reducir el número de pacientes con brotes a la semana 24. EVALUACIÓN ECONÓMICA: En cuanto a la discordancia de los estudios revisados se logra establecer que dependiendo de la perspectiva tomada en cuenta para el dimetilfumarato, se establece la efectividad o no del tratamiento, dependiendo ésto también de los tratamientos que se les compare. Donde sí existe consenso es que comparando el dimetilfumarato con acetato de glatiramer, el primero es costoefectivo. En cuanto a ocrelizumab, ambas investigaciones encontradas, desde la perspectiva del pagador, consideran que este tratamiento es costo-efectivo. Por último, teriflunomida fue costoefectivo para una investigación realizada en Finlandia desde la perspectiva del pagador. En cuanto a las recomendaciones de agencias, se aprecia que: alemtuzumab y dimetilfumarato tienden a ser recomendados, no así teriflunomide. Ocrelizumab al momento se encuentra en análisis por las agencias. En cuanto al análisis presupuestal, se encontró que los costos de los mismos para la esclerosis múltiple remitente recurrente, en 1ª línea, serían de un nivel muy alto en relación al fondo disponible. En cuando a la esclerosis múltiple primaria progresiva, el impacto de ocrelizumab para el año 2018 es de MM$4.440. Además, se realizó una comparación de cuál sería el impacto diferencial en esclerosis múltiple remitente recurrente en 2ª línea, en comparación por lo ya cubierto por la ley, de incluir Ocrelizumab o Alemtuzumab. CONCLUSIÓN: Para dar cumplimiento al artículo 28° del Reglamento que establece el proceso destinado a determinar los diagnósticos y tratamientos de alto costo con Sistema de Protección Financiera, según lo establecido en los artículos 7° y 8° de la ley N°20.850, aprobado por el decreto N° 13 del Ministerio de Salud, se concluye que el presente informe de evaluación se considera favorable, de acuerdo a lo establecido en el Título III, de las Evaluaciones Favorables de la Norma Técnica N° 0192 de este mismo Ministerio.

Bupivacaine-induced Vasodilation Is Mediated by Decreased Calcium Sensitization in Isolated Endothelium-denuded Rat Aortas Precontracted with Phenylephrine

BACKGROUND: A toxic dose of bupivacaine produces vasodilation in isolated aortas. The goal of this in vitro study was to investigate the cellular mechanism associated with bupivacaine-induced vasodilation in isolated endotheliumdenuded rat aortas precontracted with phenylephrine. METHODS: Isolated endothelium-denuded rat aortas were suspended for isometric tension recordings. The effects of nifedipine, verapamil, iberiotoxin, 4-aminopyridine, barium chloride, and glibenclamide on bupivacaine concentration-response curves were assessed in endothelium-denuded aortas precontracted with phenylephrine. The effect of phenylephrine and KCl used for precontraction on bupivacaine-induced concentration-response curves was assessed. The effects of verapamil on phenylephrine concentration-response curves were assessed. The effects of bupivacaine on the intracellular calcium concentration ([Ca2+]i) and tension in aortas precontracted with phenylephrine were measured simultaneously with the acetoxymethyl ester of a fura-2-loaded aortic strip. RESULTS: Pretreatment with potassium channel inhibitors had no effect on bupivacaine-induced relaxation in the endothelium-denuded aortas precontracted with phenylephrine, whereas verapamil or nifedipine attenuated bupivacaine-induced relaxation. The magnitude of the bupivacaine-induced relaxation was enhanced in the 100 mM KCl-induced precontracted aortas compared with the phenylephrine-induced precontracted aortas. Verapamil attenuated the phenylephrine-induced contraction. The magnitude of the bupivacaine-induced relaxation was higher than that of the bupivacaine-induced [Ca2+]i decrease in the aortas precontracted with phenylephrine. CONCLUSIONS: Taken together, these results suggest that toxic-dose bupivacaine-induced vasodilation appears to be mediated by decreased calcium sensitization in endothelium-denuded aortas precontracted with phenylephrine. In addition, potassium channel inhibitors had no effect on bupivacaine-induced relaxation. Toxic-dose bupivacaine- induced vasodilation may be partially associated with the inhibitory effect of voltage-operated calcium channels.

Mechanisms of phytoestrogen biochanin A-induced vasorelaxation in renovascular hypertensive rats

BACKGROUND: The plant-derived estrogen biochanin A is known to cause vasodilation, but its mechanism of action in hypertension remains unclear. This study was undertaken to investigate the effects and mechanisms of biochanin A on the thoracic aorta in two-kidney, one clip (2K1C) renovascular hypertensive rats. METHODS: Hypertension was induced by clipping the left renal artery, and control age-matched rats were sham treated. Thoracic aortae were mounted in tissue baths to measure isometric tension. RESULTS: Biochanin A caused concentration-dependent relaxation in aortic rings from 2K1C hypertensive and sham-treated rats, which was greater in 2K1C rats than in sham rats. Biochanin A-induced relaxation was significantly attenuated by removing the endothelium in aortic rings from 2K1C rats, but not in sham rats. Nomega-Nitro-L-arginine methylester, a nitric oxide synthase inhibitor, or indomethacin, a cyclooxygenase inhibitor, did not affect the biochanin A-induced relaxation in aortic rings from 2K1C and sham rats. By contrast, treatment with glibenclamide, a selective inhibitor of adenosine triphosphate-sensitive K+ channels, ortetraethy-lammonium, an inhibitor of Ca2+-activated K+ channels, significantly reduced biochanin A-induced relaxation in aortic rings from both groups. However, 4-aminopyridine, a selective inhibitor of voltage-dependent K+ channels, inhibited the relaxation induced by biochanin A in 2K1C rats, whereas no significant differences were observed in sham rats. CONCLUSION: These results suggest that the enhanced relaxation caused by biochanin A in aortic rings from hypertensive rats is endothelium dependent. Vascular smooth muscle K+ channels may be involved in biochanin A-induced relaxation in aortae from hypertensive and normotensive rats. In addition, an endothelium-derived activation of voltage-dependent K+ channels contributes, at least in part, to the relaxant effect of biochanin A in renovascular hypertension.

4-Aminopyridine Improves Lower Urinary Tract Symptoms in a Patient With Benign Prostatic Hyperplasia and Downbeat Nystagmus Syndrome / 대한배뇨장애요실금학회지

Aminopyridines are potassium channel blockers that increase the excitability of nerve cells and axons; therefore, they are widely used to treat different neurological disorders. Here we present a patient with idiopathic downbeat nystagmus and lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia who was treated with the sustained-release form of 4-aminopyridine (4-AP). During treatment with 4-AP, the LUTS improved. This improvement was monitored by using uroflowmetry and the International Prostate Symptom Score. A significant improvement of symptoms was observed in relation to the voided volume. This included an improved emptying of the bladder without an increase in residual urine. In animal studies, both nonselective K+ channel blockade and selective voltage-sensitive potassium blockade by 4-AP resulted in increased contraction on rat detrusor strips. To our knowledge, this is the first clinical observation of the mode of action of 4-AP in urological symptoms in humans.

Age-related changes in transient outward potassium current of rat ventricular myocyte / 生理学报

The study aimed to investigate the age-related changes and drug reactions of transient outward potassium current (Ito) of ventricular myocytes. Twenty-eight Sprague Dawley rats were divided into young (3-5 months), adult (13-15 months) and aged (22-24 months) groups, and Ito currents of isolated myocytes from each group were recorded respectively by patch-clamp. The perfusion of 2.0 mmol/L 4-AP or 1.0 μmol/L isoproterenol was added respectively in each group, and the changes of Ito were observed. In comparison with young and adult groups, Ito densities of ventricular myocytes in aged group was significantly increased, the curve of steady-state activation of Ito shifted to the left, the close-state inactivation rate significantly decreased, and recovery rate from the steady-state inactivation became quicker. However, no significant changes could be detected for the Ito steady-state inactivation of ventricular myocytes in aged group. The similar responsiveness to 4-AP was observed in all three groups, but the responsiveness to isoproterenol was weaker in the aged group (55.9%) than in the other two groups (127.5% and 125.8%). In conclusion, the results show that Ito of rat ventricular myocyte of aging heart has increased current density and decreased response to isoproterenol.

Serotonin contracts the rat mesenteric artery by inhibiting 4-aminopyridine-sensitive Kv channels via the 5-HT2A receptor and Src tyrosine kinase

Serotonin (5-hydroxytryptamine (5-HT)) is a neurotransmitter that regulates a variety of functions in the nervous, gastrointestinal and cardiovascular systems. Despite such importance, 5-HT signaling pathways are not entirely clear. We demonstrated previously that 4-aminopyridine (4-AP)-sensitive voltage-gated K+ (Kv) channels determine the resting membrane potential of arterial smooth muscle cells and that the Kv channels are inhibited by 5-HT, which depolarizes the membranes. Therefore, we hypothesized that 5-HT contracts arteries by inhibiting Kv channels. Here we studied 5-HT signaling and the detailed role of Kv currents in rat mesenteric arteries using patch-clamp and isometric tension measurements. Our data showed that inhibiting 4-AP-sensitive Kv channels contracted arterial rings, whereas inhibiting Ca2+-activated K+, inward rectifier K+ and ATP-sensitive K+ channels had little effect on arterial contraction, indicating a central role of Kv channels in the regulation of resting arterial tone. 5-HT-induced arterial contraction decreased significantly in the presence of high KCl or the voltage-gated Ca2+ channel (VGCC) inhibitor nifedipine, indicating that membrane depolarization and the consequent activation of VGCCs mediate the 5-HT-induced vasoconstriction. The effects of 5-HT on Kv currents and arterial contraction were markedly prevented by the 5-HT2A receptor antagonists ketanserin and spiperone. Consistently, alpha-methyl 5-HT, a 5-HT2 receptor agonist, mimicked the 5-HT action on Kv channels. Pretreatment with a Src tyrosine kinase inhibitor, 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine, prevented both the 5-HT-mediated vasoconstriction and Kv current inhibition. Our data suggest that 4-AP-sensitive Kv channels are the primary regulator of the resting tone in rat mesenteric arteries. 5-HT constricts the arteries by inhibiting Kv channels via the 5-HT2A receptor and Src tyrosine kinase pathway.

Mechanism of Relaxation Via TASK-2 Channels in Uterine Circular Muscle of Mouse

Plasma pH can be altered during pregnancy and at labor. Membrane excitability of smooth muscle including uterine muscle is suppressed by the activation of K+ channels. Because contractility of uterine muscle is regulated by extracellular pH and humoral factors, K+ conductance could be connected to factors regulating uterine contractility during pregnancy. Here, we showed that TASK-2 inhibitors such as quinidine, lidocaine, and extracellular acidosis produced contraction in uterine circular muscle of mouse. Furthermore, contractility was significantly increased in pregnant uterine circular muscle than that of non-pregnant muscle. These patterns were not changed even in the presence of tetraetylammonium (TEA) and 4-aminopyridine (4-AP). Finally, TASK-2 inhibitors induced strong myometrial contraction even in the presence of L-methionine, a known inhibitor of stretchactivated channels in myometrium. When compared to non-pregnant myometrium, pregnant myometrium showed increased immunohistochemical expression of TASK-2. Therefore, TASK-2, seems to play a key role during regulation of myometrial contractility in the pregnancy and provides new insight into preventing preterm delivery.

Disappearance of Hypoxic Pulmonary Vasoconstriction and O2-Sensitive Nonselective Cationic Current in Arterial Myocytes of Rats Under Ambient Hypoxia

Acute hypoxia induces contraction of pulmonary artery (PA) to protect ventilation/perfusion mismatch in lungs. As for the cellular mechanism of hypoxic pulmonary vasoconstriction (HPV), hypoxic inhibition of voltage-gated K+ channel (Kv) in PA smooth muscle cell (PASMC) has been suggested. In addition, our recent study showed that thromboxane A2 (TXA2) and hypoxia-activated nonselective cation channel (I(NSC)) is also essential for HPV. However, it is not well understood whether HPV is maintained in the animals exposed to ambient hypoxia for two days (2d-H). Specifically, the associated electrophysiological changes in PASMCs have not been studied. Here we investigate the effects of 2d-H on HPV in isolated ventilated/perfused lungs (V/P lungs) from rats. HPV was almost abolished without structural remodeling of PA in 2d-H rats, and the lost HPV was not recovered by Kv inhibitor, 4-aminopyridine. Patch clamp study showed that the hypoxic inhibition of Kv current in PASMC was similar between 2d-H and control. In contrast, hypoxia and TXA2-activated I(NSC) was not observed in PASMCs of 2d-H. From above results, it is suggested that the decreased I(NSC) might be the primary functional cause of HPV disappearance in the relatively early period (2 d) of hypoxia.

Design, synthesis and activities of 4-(2-acetoxybenzoylamino) butyramide derivatives / 药学学报

To explore new agents of gamma-aminobutyric acid (GABA) derivatives with more potent antiepileptic activity, a series of 4-(2-acetoxybenzoylamino) butyramide derivatives were designed and synthesized. All of the novel compounds (5a-51) were synthesized from GABA as starting material, and their structures were confirmed with IR, 1H NMR, EI-MS and elemental analysis. Preliminary pharmacological test in vitro showed that all target compounds displayed strong antiepileptic activities and were worth for further study. The structure-activity relationship of 4-(2-acetoxybenzoylamino) butyramide derivatives was also discussed preliminarily.

Synthesis and activities of 4-(2-acetoxybenzoylamino) butyramide heterocyclic compounds / 药学学报

It has been demonstrated by our previous research that 4-(2-acetoxybenzoylamino) butyramide derivatives exhibited good antiepileptic activities. In this paper, to explore the SAR and improve the antiepileptic activities of these derivatives, a series of novel 4-(2-acetoxybenzoylamino) butyramide heterocyclic compounds (5a-5n) were synthesized and biologically evaluated. Their structures were confirmed by 1H MNR, ESI-MS and elemental analysis. Pharmacological test in vivo showed that target compounds (5f, 5i-5n) displayed strong antiepileptic activities on 4-AP induced epilepsy in mice with ED50 values ranging from 0.3137 to 0.3604 mmol x kg(-1).

A Novel Pathway Underlying the Inhibitory Effects of Melatonin on Isolated Rat Urinary Bladder Contraction

The aim of the present study was to elucidate the direct effects of melatonin on bladder activity and to determine the mechanisms responsible for the detrusor activity of melatonin in the isolated rat bladder. We evaluated the effects of melatonin on the contractions induced by phenylephrine (PE), acetylcholine (ACh), bethanechol (BCh), KCl, and electrical field stimulation (EFS) in 20 detrusor smooth muscle samples from Sprague-Dawley rats. To determine the mechanisms underlying the inhibitory responses to melatonin, melatonin-pretreated muscle strips were exposed to a calcium channel antagonist (verapamil), three potassium channel blockers [tetraethyl ammonium (TEA), 4-aminopyridine (4-AP), and glibenclamide], a direct voltage-dependent calcium channel opener (Bay K 8644), and a specific calcium/calmodulin-dependent kinase II (CaMKII) inhibitor (KN-93). Melatonin pretreatment (10(-8)~10(-6) M) decreased the contractile responses induced by PE (10(-9)~10(-4) M) and Ach (10(-9)~10(-4) M) in a dose-dependent manner. Melatonin (10(-7) M) also blocked contraction induced by high KCl ([KCl]ECF; 35 mM, 70 mM, 105 mM, and 140 mM) and EFS. Melatonin (10(-7) M) potentiated the relaxation response of the strips by verapamil, but other potassium channel blockers did not change melatonin activity. Melatonin pretreatment significantly decreased contractile responses induced by Bay K 8644 (10(-11)~10(-7) M). KN-93 enhanced melatonin-induced relaxation. The present results suggest that melatonin can inhibit bladder smooth muscle contraction through a voltage-dependent, calcium-antagonistic mechanism and through the inhibition of the calmodulin/CaMKII system.

High K(+)-Induced Relaxation by Nitric Oxide in Human Gastric Fundus

This study was designed to elucidate high K(+)-induced relaxation in the human gastric fundus. Circular smooth muscle from the human gastric fundus greater curvature showed stretch-dependent high K+ (50 mM)-induced contractions. However, longitudinal smooth muscle produced stretch-dependent high K(+)-induced relaxation. We investigated several relaxation mechanisms to understand the reason for the discrepancy. Protein kinase inhibitors such as KT 5823 (1 microM) and KT 5720 (1 microM) which block protein kinases (PKG and PKA) had no effect on high K(+)-induced relaxation. K+ channel blockers except 4-aminopyridine (4-AP), a voltage-dependent K+ channel (KV) blocker, did not affect high K(+)-induced relaxation. However, N(G)-nitro-L-arginine and 1H-(1,2,4)oxadiazolo (4,3-A)quinoxalin-1-one, an inhibitors of soluble guanylate cyclase (sGC) and 4-AP inhibited relaxation and reversed relaxation to contraction. High K(+)-induced relaxation of the human gastric fundus was observed only in the longitudinal muscles from the greater curvature. These data suggest that the longitudinal muscle of the human gastric fundus greater curvature produced high K(+)-induced relaxation that was activated by the nitric oxide/sGC pathway through a KV channel-dependent mechanism.

Design, synthesis and antiepileptic activity of 4-(2-acetoxybenzoylamino) butyrate derivatives / 药学学报

A series of 4-(2-acetoxybenzoylamino) butyrate derivatives were designed and synthesized. All of the novel 12 compounds (7a-7k) were synthesized from gamma-aminobutyric acid (1) as starting material, and their structures were confirmed with IR, 1H NMR, EI-MS and elemental analysis. Preliminary pharmacological test in vitro showed that most of these title compounds possessed antiepileptic activity. Compounds 7i-7k displayed strong antiepileptic activity and are worth for further development. Compounds 4, 7d-7h showed moderate antiepileptic activity. The structure-activity relationship of 4-(2-acetoxybenzoylamino) butyrate derivatives is also discussed preliminarily.

Mechanism of vasodilation by propofol in the rabbit renal artery

BACKGROUND: Propofol directly inhibits vascular reactivity. However, available information regarding the underlying mechanisms of propofol is poor. Therefore, mechanisms of the underlying relaxant action of propofol were investigated using rabbit renal arteries. METHODS: Propofol-induced relaxation of rabbit renal arteries was studied in contracted preparations with 50 mM KCl or 10microM histamine. Vessel tension was recorded with a pen recorder. We were interested in determining whether propofol-induced vasodilation is affected by endothelium-denudation, L-NG-nitroarginine methyl ester (L-NAME), tetraethylammonium (TEA), iberiotoxin, glibenclamide, 4-aminopyridine, 7-ethoxyresorufin, caffeic acid, baiclalein, ryanodine, and thapsigargin. RESULTS: Propofol-induced concentration-dependent vasodilation was not affected either by endothelium denudation or by L-NAME during histamine-induced contraction. The relaxing effect of propofol on histamine-induced contraction was inhibited by either TEA, a K+ channel inhibitor, or iberiotoxin (100 nM), a selective blocker of the large conductance Ca(2+)-activated K+ channel (BKCa channel). In contrast, the relaxing effect of propofol was unaffected by 10microM glibenclamide, an ATP-sensitive K+ channel blocker, by 5 mM 4-aminopyridine, a blocker of delayed rectifier, by 7-ethoxyresorufin, a cytochrome P450 inhibitor, by 10microM caffeic acid and 10microM baiclalein, lipooxygenase inhibitors, or by 10microM ryanodine and thapsigargin, Ca2+store inhibitors. CONCLUSIONS: These results suggest that the relaxant effect of propofol may result from activation of BKCa channels by inhibiting voltage-gated Ca2+ influx in a prolonged manner.

Effects of telmisartan on 4-Aminopyridine-sensitive voltage dependant potassium channel of lymphocyte derived from spontaneously hypertensive rat / 中华心血管病杂志

<p><b>OBJECTIVE</b>To study the effects of telmisartan on voltage dependant potassium channel (Kv) expression in lymphocytes from spontaneously hypertensive rat (SHR).</p><p><b>METHODS</b>Peripheral blood was collected from male SHR aged 16 and 4 weeks. Peripheral lymphocytes were separated from heparinized whole blood by standard Ficoll-Hypaque density gradient centrifugation. The whole-cell Kv currents were recorded with patch-clamp technique in the absence and presence of telmisartan(10, 30, 100 µmol/L). Real-time PCR was used to determine Kv1.3 mRNA expression in lymphocytes.</p><p><b>RESULTS</b>(1) The currents density of Kv was higher in lymphocytes from 16 weeks-old SHR [ (119.0 ± 9.6) pA/pF] than from 4 weeks-old SHR [(59.0 ± 7.2) pA/pF, P < 0.05]. (2) Currents density was positively correlated with systolic blood pressure in 16 weeks-old SHR (r = 0.837, P < 0.05). (3) The lymphocytes Kv 1.3 mRNA expression was significantly higher in 16-weeks-old SHR than in 4-weeks-old SHR (P < 0.05). (4) Telmisartan reduced the whole-cell Kv currents in a concentration-dependent manner (10.5 ± 3.4)% at 10 µmol/L, (45.8 ± 3.7)% at 30 µmol/L and (81.6 ± 4.2)% at 100 µmol/L, P < 0.01.</p><p><b>CONCLUSIONS</b>The lymphocyte Kv channel is upregulated in 16 weeks-old SHR suggesting a role of Kv in the pathophysiology of hypertension. Kv current in lymphocyte could be significantly blocked by telmisartan in a concentration dependent manner.</p>