RESUMEN
Despite the consensus that activation of TWIK-related spinal cord K+ (TRESK) might contribute to the pathogenesis of chronic pain, the specific mechanisms underlying the transfer and development of pain signals still remain obscure. In the present study, we validated that TRESK was expressed in neurons instead of glial cells. Furthermore, in the SNI model of neuropathic pain (NP), downregulation of TRESK in spinal cord neurons resulted in upregulation of connexin 36 (Cx36) and connexin 43 (Cx43), both being subtypes of gap junctions in the spinal cord, with gliocytes in the spinal cord activated ultimately. Compared with SNI rats, intrathecal injection of TRESK gene recombinant adenovirus significantly downregulated the expression levels of Cx36 and Cx43 and suppressed the activation of gliocytes in the spinal cord, with hyperalgesia significantly reduced. In conclusion, TRESK contributes to the pathogenesis of NP by upregulation of synaptic transmission and activation of gliocytes.
Asunto(s)
Regulación hacia Abajo/fisiología , Neuralgia/metabolismo , Neuralgia/prevención & control , Neuroglía/metabolismo , Canales de Potasio/metabolismo , Médula Espinal/metabolismo , Adenoviridae , Animales , Astrocitos/efectos de los fármacos , Astrocitos/metabolismo , Astrocitos/patología , Regulación hacia Abajo/efectos de los fármacos , Inyecciones Espinales , Masculino , Neuralgia/patología , Neuroglía/efectos de los fármacos , Neuroglía/patología , Canales de Potasio/administración & dosificación , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Médula Espinal/efectos de los fármacos , Médula Espinal/patologíaRESUMEN
OBJECTIVE: To characterize pathogenic effects of antibodies to dipeptidyl-peptidase-like protein 6 (DPPX), a subunit of Kv4.2 potassium channels, on gut and brain neurons. METHODS: We identified a new patient with anti-DPPX encephalitis and analyzed the effects of the patient's serum and purified immunoglobulin G (IgG), and of serum of a previous patient with anti-DPPX encephalitis, on the activity of enteric neurons by voltage-sensitive dye imaging in guinea pig myenteric and human submucous plexus preparations. We studied the subcellular localization of DPPX by immunocytochemistry in cultured murine hippocampal neurons using sera of 4 patients with anti-DPPX encephalitis. We investigated the influence of anti-DPPX-containing serum and purified IgG on neuronal surface expression of DPPX and Kv4.2 by immunoblots of purified murine hippocampal neuron membranes. RESULTS: The new patient with anti-DPPX encephalitis presented with a 2-month episode of diarrhea, which was followed by tremor, disorientation, and mild memory impairment. Anti-DPPX-IgG-containing sera and purified IgG increased the excitability and action potential frequency of guinea pig and human enteric nervous system neurons. Patient sera revealed a somatodendritic and perisynaptic neuronal surface staining that colocalized with the signal of commercial anti-DPPX and Kv4.2 antibodies. Incubation of hippocampal neurons with patient serum and purified IgG resulted in a decreased expression of DPPX and Kv4.2 in neuronal membranes. CONCLUSIONS: Hyperexcitability of enteric nervous system neurons and downregulation of DPPX and Kv4.2 from hippocampal neuron membranes mirror the clinical phenotype of patients with anti-DPPX encephalitis and support a pathogenic role of anti-DPPX antibodies in anti-DPPX encephalitis.
Asunto(s)
Anticuerpos Antiidiotipos/sangre , Encéfalo/patología , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/sangre , Encefalitis/sangre , Plexo Mientérico/patología , Proteínas del Tejido Nervioso/sangre , Neuronas/patología , Canales de Potasio/sangre , Anciano , Animales , Anticuerpos Antiidiotipos/administración & dosificación , Encéfalo/efectos de los fármacos , Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/administración & dosificación , Encefalitis/diagnóstico , Cobayas , Humanos , Inmunoglobulina G/administración & dosificación , Inmunoglobulina G/sangre , Masculino , Ratones , Plexo Mientérico/efectos de los fármacos , Proteínas del Tejido Nervioso/administración & dosificación , Neuronas/efectos de los fármacos , Canales de Potasio/administración & dosificación , RatasRESUMEN
Necrotic insults such as seizure are excitotoxic. Logically, membrane hyperpolarization by increasing outwardly conducting potassium channel currents should attenuate hyperexcitation and enhance neuron survival. Therefore, we overexpressed a small-conductance calcium-activated (SK2) or voltage-gated (Kv1.1) channel via viral vectors in cultured hippocampal neurons. We found that SK2 or Kv1.1 protected not only against kainate or glutamate excitotoxicity but also increased survival after sodium cyanide or staurosporine. In vivo overexpression of either channel in dentate gyrus reduced kainate-induced CA3 lesions. In hippocampal slices, the kainate-induced increase in granule cell excitability was reduced by overexpression of either channel, suggesting that these channels exert their protective effects during hyperexcitation. It is also important to understand any functional disturbances created by transgene overexpression alone. In the absence of insult, overexpression of Kv1.1, but not SK2, reduced baseline excitability in dentate gyrus granule cells. Furthermore, while no behavioral disturbances during spatial acquisition in the Morris water maze were observed with overexpression of either channel, animals overexpressing SK2, but not Kv1.1, exhibited a memory deficit post-training. This difference raises the possibility that the means by which these channel subtypes protect may differ. With further development, potassium channel vectors may be an effective pre-emptive strategy against necrotic insults.
Asunto(s)
Apoptosis/fisiología , Terapia Genética/métodos , Neuronas/metabolismo , Canales de Potasio Calcio-Activados , Canales de Potasio con Entrada de Voltaje , Canales de Potasio/genética , Canales de Potasio/metabolismo , Animales , Apoptosis/efectos de los fármacos , Muerte Celular , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Agonistas de Aminoácidos Excitadores/toxicidad , Expresión Génica , Terapia Genética/efectos adversos , Hipocampo/citología , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Técnicas In Vitro , Canal de Potasio Kv.1.1 , Masculino , Aprendizaje por Laberinto/efectos de los fármacos , Trastornos de la Memoria/genética , Neuronas/efectos de los fármacos , Canales de Potasio/administración & dosificación , Ratas , Ratas Sprague-Dawley , Canales de Potasio de Pequeña Conductancia Activados por el Calcio , Cianuro de Sodio/toxicidadRESUMEN
The abilities of such therapeutic nitrovasodilators as sodium nitroprusside (SNP) and glyceryl trinitrate (GTN) to dilate vascular smooth muscles (VSM) and affect intracellular calcium concentration level ([Ca2+]i) in a rat tail artery were tested under different types of preactivation. To shed light on mechanisms underlying possible differences in the action of these two nitric oxide (NO) donors, simultaneous measurements of [Ca2+]i and contractile force were done. All vascular rings were precontracted either using a high-K+-Krebs solution or phenylephrine (PE). It was shown that the effect of both NO donors strongly depended on a type of VSM preactivation. The EC50 for GTN under K+ stimulation of VSM comprised (2.48 +/- 1.6) x 10(-5) M, whereas the mean EC50 under PE stimulation was (3.05 +/- 2.3) x 10(-4) M (p < 0.05, n = 9). The EC50 for SNP under K+ stimulation of VSM comprised (1.09 +/- 0.47) x 10(-7) M, whereas the EC(50) under PE stimulation was (8.01 +/- 2.4) x 10(-6) M (p < 0.05, n = 9). GTN demonstrated a significant discrepancy in the magnitude of changes in [Ca2+]i and related VSM relaxant responses, indicating the ability of GTN to relax VSM in the absence of a proportional decrease in [Ca2+]i. The main peculiarity of SNP action under K+ stimulation as compared to PE stimulation was the transient decrease in [Ca2+]i while relaxation was sustained. Therefore, both NO donors demonstrated their ability to produce vasorelaxation as a result of an alteration in myofilament calcium sensitivity. These data clearly indicate that the sensitivity of VSM to NO donors is higher under K+ depolarization than that seen under PE stimulation, indicating that Ca2+ entry through voltage-operated calcium channels is more sensitive to NO as compared to calcium mobilization by means of Ca2+ entry through receptor- operated calcium channels or intracellular Ca2+ release, or both.
Asunto(s)
Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/fisiología , Donantes de Óxido Nítrico/administración & dosificación , Animales , Canales de Calcio/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Soluciones Isotónicas/administración & dosificación , Masculino , Modelos Animales , Modelos Cardiovasculares , Contracción Miocárdica/efectos de los fármacos , Nitroglicerina/administración & dosificación , Nitroprusiato/administración & dosificación , Fenilefrina/administración & dosificación , Canales de Potasio/administración & dosificación , Ratas , Ratas Wistar , Estimulación Química , Grado de Desobstrucción Vascular/efectos de los fármacos , Vasoconstrictores/administración & dosificación , Vasodilatadores/administración & dosificaciónRESUMEN
AIMS: Measurement of electrocardiographic intervals to assess dispersion in ventricular repolarization may be helpful in the assessment of the risk of ventricular arrhythmia. We measured QTc, QT dispersion, and T wave intervals in premature infants before and while on treatment with the I(Kr) blocker cisapride as markers for dispersion in ventricular repolarization. METHODS AND RESULTS: We enrolled 15 non-ventilated premature infants with a mean gestational age of 30.5 weeks, ranging from 26.5 to 33.5 weeks, and mean postnatal age of 24 days, with a range from 5 to 51 days. A digital 12 lead electrocardiogram was recorded prior to and 3 days after administering cisapride at a dose of 0.8 mg/kg/day. Serum electrolytes were simultaneously measured. Electrocardiographic measurements before and after included: QT, QTc Bazett, QT dispersion, R-R, T wave interval peak to end, T wave interval peak to end/onset Q to T wave peak, T wave axis, T wave maximum voltage and QRS-T angle. A paired t test and analysis of variance was used to compare the variables before and during treatment. The QTc, T wave interval peak to end and the ratio T wave interval peak to end/onset Q to T peak increased significantly following treatment with cisapride. Results expressed as before and during treatment were for QTc: 429 (65) ms versus 454 (29) ms p < 0.02; for T wave interval peak to end: 65 (11) ms versus 103 (24) p <0.01, for the ratio T wave interval peak to end/onset Q to T peak: 0.32 (0.06) versus 0.55 (0.16) p < 0.001. Treatment with the I(Kr) blocker did not significantly alter the QT dispersion, T wave voltage, angle or QRS-T angle. CONCLUSION: The interval from the peak to the end of the T wave and the ratio of this value to the onset Q to T peak interval, represents regional dispersion of repolarization across the ventricular wall. This is a potentially useful clinical index in the assessment of arrhythmic risk in premature infants being treated by blockade of the I(Kr) channels.
Asunto(s)
Proteínas de Transporte de Catión , Cisaprida/antagonistas & inhibidores , Proteínas de Unión al ADN , Electrocardiografía , Recien Nacido Prematuro , Bloqueadores de los Canales de Potasio , Canales de Potasio con Entrada de Voltaje , Transactivadores , Bélgica , Cisaprida/administración & dosificación , Canal de Potasio ERG1 , Canales de Potasio Éter-A-Go-Go , Humanos , Lactante , Bienestar del Lactante , Recién Nacido , Síndrome de QT Prolongado/complicaciones , Síndrome de QT Prolongado/tratamiento farmacológico , Síndrome de QT Prolongado/epidemiología , Canales de Potasio/administración & dosificación , Factores de Riesgo , Regulador Transcripcional ERG , Complejos Prematuros Ventriculares/epidemiología , Complejos Prematuros Ventriculares/etiologíaRESUMEN
PURPOSE: To investigate the effects of the new K(ATP) channel opener, ZD6169, shown to have an in vivo selectivity for the bladder, on bladder activity in rats. MATERIALS AND METHODS: ZD6169 was given intra-arterially (i.a., 0.1 and 1 mg./kg.) or orally (3 mg./kg.) to conscious Sprague-Dawley rats undergoing continuous cystometry. Investigations were also performed before and after stimulation of bladder activity by intravesical prostaglandin (PG) E2. RESULTS: Intra-arterial ZD6169 increased residual volume, but caused no changes in other cystometric parameters. In rats receiving oral ZD6169, cystometric parameters were compared (every hour up to five hours) to those recorded in rats receiving oral vehicle. No differences were found, except in threshold pressure, which was significantly increased. Intravesical PGE2 20 microM increased micturition and basal pressures, and decreased bladder capacity and micturition volume. ZD6169 1 mg./kg., given i.a., reduced or completely prevented the activity induced by intravesical PGE2. Three hours after orally administered ZD6169 (3 mg./kg.), intravesical PGE2 20 microM had no effect. Three hours after oral administration of vehicle, the effects of PGE2 were attenuated, but still statistically significant. CONCLUSIONS: ZD6169, given i.a. or orally, increased threshold pressure, but had otherwise little effect on volume-induced micturition. However, the drug markedly reduced or prevented PGE2-induced bladder activity when given i.a.; it was also effective when given orally. If ZD6169 has inhibiting effects on bladder contraction in man without any cardiovascular actions, the drug may represent a novel, promising way of treating bladder overactivity.
Asunto(s)
Amidas/farmacología , Benzofenonas/farmacología , Dinoprostona/fisiología , Canales de Potasio/fisiología , Vejiga Urinaria/efectos de los fármacos , Vejiga Urinaria/fisiología , Administración Intravesical , Administración Oral , Amidas/administración & dosificación , Animales , Benzofenonas/administración & dosificación , Inyecciones Intraarteriales , Canales de Potasio/administración & dosificación , Ratas , Ratas Sprague-DawleyRESUMEN
We studied the effects of two active dose levels of dofetilide (8 and 12 micrograms/kg) and placebo in 16 patients with recent onset atrial fibrillation. The study was of a crossover design such that all patients received a therapeutic agent, 15 patients completed the study. Cardioversion was achieved in 2/6 patients receiving 8 micrograms/kg dofetilide and in 2/9 patients receiving 12 micrograms/kg. No patients cardioverted as a result of the placebo infusion. Two patients who cardioverted suffered episodes of torsades de pointes following the active drug. Electrical cardioversion was attempted in eight patients who remained in atrial fibrillation and was successful in six. The average duration of atrial fibrillation was 35 days in those who cardioverted and 83 days in those who did not. The compound appears to have only limited effect in cardioversion of atrial fibrillation of moderate duration.