I1363T mutation induces the defects in fast inactivation of human skeletal muscle voltage-gated sodium channel / 浙江大学学报·医学版

OBJECTIVE@#To investigate the mechanism of congenital paramyotonia caused by human skeletal muscle voltage-gated sodium channel hNav1.4 mutant I1363T.@*METHODS@#The conservation of the mutant site were detecled by using amino acid sequence alignment; the C-terminal mCherry fusion hNav1.4 was constructed, and the expression and distribution of wild type and hNav1.4 mutant I1363T were determined by confocal microscopy; the steady-state activation, fast inactivation and window current of wild type and hNav1.4 mutant I1363T were examined by whole-cell patch clamp.@*RESULTS@#Alignment of the amino acid sequences revealed that Ile1363 is highly conserved in human sodium channels. There was no significant difference in expression level and distribution between wild type and I1363T. Although no significant differences were observed between I1363T mutant and wild type in the activation upon channel gating, the of voltage-dependence of fast inactivation of I1363T mutant[(-59.01±0.26) mV] shifted 9 mV towards depolarization as compared with wild type[(-68.03±0.34) mV], and the slope factor of voltage-dependence curve increased to (5.24±0.23) mV, compared with (4.55±0.21) mV of the wild type. Moreover, I1363T showed the larger window current than that of the wild type.@*CONCLUSIONS@#I1363T causes the defect in fast inactivation of hNav1.4, which may increase the excitability of muscle cells and be responsible for myotonia. The increased window current of I1363T may result in an increase of inward Na+ current, could subsequently inactivate the channels and lead to loss of excitability and paralysis.

Structural modeling of selectivity filter in transient receptor pontential melastatin 8 ion channel / 浙江大学学报·医学版

OBJECTIVE@#To construct a three-dimensional structural model for the selectivity filter in the transient receptor pontential melastatin 8 (TRPM8) ion channel.@*METHODS@#In the Rosetta computational structural biology suite, multiple rounds of modeling with the kinematic loop closure algorithm were performed.@*RESULTS@#After nine rounds of computational modeling, we obtained the models of the selectivity filter within the TRPM8 channel with the lowest energy and high convergence. The model showed that the sidechain of D918 points were away from the central ion permeation pathway, while the sidechains of Q914, D920 and T923 pointed towards it. The glycosylation site N934 was located outside the pore region and its side chain directed to the extracellular water environment.@*CONCLUSIONS@#A three-dimensional structural model for the selectivity filter in the TRPM8 ion channel was constructed, which provides reliable structural information for exploring the mechanism of ion selectivity.

Progress on structural biology of voltage-gated ion channels / 浙江大学学报·医学版

Ion channels mediate ion transport across membranes, and play vital roles in processes of matter exchange, energy transfer and signal transduction in living organisms. Recently, structural studies of ion channels have greatly advanced our understanding of their ion selectivity and gating mechanisms. Structural studies of voltage-gated potassium channels elucidate the structural basis for potassium selectivity and voltage-gating mechanism; structural studies of voltage-gated sodium channels reveal their slow and fast inactivation mechanisms; and structural studies of transient receptor potential (TRP) channels provide complex and diverse structures of TRP channels, and their ligand gating mechanisms. In the article we summarize recent progress on ion channel structural biology, and outlook the prospect of ion channel structural biology in the future.

Canales iónicos Receptores de Potencial Transitorio y su papel protagónico en la terapia analgésica / Transient receptor potential ion channels and their leading role in analgesic therapy

En la búsqueda de nuevas opciones terapéuticas para el tratamiento del dolor, se ha llegado al descubrimiento de canales iónicos que actúan como receptores y están presentes en neuronas nociceptoras aferentes primarias. Entre estos receptores, se encuentran los canales iónicos receptores de potencial transitorio que regulan las vías involucradas en el dolor y la nocicepción. Se realizó una revisión actualizada de los principales canales iónicos receptores de potencial transitorio implicados en la fisiopatología del dolor. Se hace una reseña histórica del descubrimiento de estas moléculas y sus estudios avanzados. A continuación se revisan las diferentes familias de estos canales con su clasificación, nomenclatura, estructura y funciones celulares. También se hace un recuento de la relación de estos canales con la analgesia, así como el mecanismo de acción de algunos analgésicos que actúan sobre ellos. Finalmente, se detallan importantes consideraciones a tomar en cuenta, que pudieran influir sobre la utilización de estos medicamentos en la clínica. Por tal motivo, el trabajo procura ser una revisión que abarque el rol de los canales TRP como nuevas dianas farmacológicas en el tratamiento del dolor.

In the search for new therapeutic options for pain treatment, new ion channels have been discovered, which act as receptors and are present in primary afferent nociceptor neurons. Some of them are the transient receptor potential ion channels that regulate the pathways involved in pain and nociception. An updated review of the main transient potential receptors ion channels involved in pain physiopathology and a historical review of the discovery of these molecules and advanced studies on them were also made. Then the different families of these channels with their classification, nomenclature, structure and cell functions were also examined. An account of the relationships of these channels with analgesia as well as the mechanism of action of some analgesics acting upon them was also presented. Finally, important considerations were given, which should be taken into account since they might influence on the clinical use of these drugs. For these reasons, the paper intends to be a review covering the role of the transient receptor potential channels as new pharmacological targets in the pain treatment.

Indirect orthodontic bonding - a modified technique for improved efficiency and precision

INTRODUCTION: The indirect bonding technique optimizes fixed appliance installation at the orthodontic office, ensuring precise bracket positioning, among other advantages. In this laboratory clinical phase, material and methods employed in creating the transfer tray are decisive to accuracy. OBJECTIVE: This article describes a simple, efficient and reproducible indirect bonding technique that allows the procedure to be carried out successfully. Variables influencing the orthodontic bonding are analyzed and discussed in order to aid professionals wishing to adopt the indirect bonding technique routinely in their clinical practice. .

INTRODUÇÃO: a técnica de colagem indireta prioriza a otimização do procedimento de montagem do aparelho fixo na clínica ortodôntica, assegurando, entre outras, vantagens relacionadas à precisão no posicionamento dos braquetes. Nesse procedimento clínico laboratorial, o material e o método de confecção da moldeira de transferência são determinantes no quesito precisão. OBJETIVO: este artigo descreve uma técnica de colagem indireta simples, eficiente e reprodutível, para que o procedimento possa ser realizado com sucesso. Variáveis que exercem influência sobre o procedimento são analisadas e discutidas, a fim de auxiliar o profissional a adotar, de forma rotineira, a técnica de colagem indireta em sua prática clínica. .

Evolution of mammographic image quality in the state of Rio de Janeiro / A evolução da qualidade da imagem em mamografia no Estado do Rio de Janeiro

Objective: To evaluate the evolution of mammographic image quality in the state of Rio de Janeiro on the basis of parameters measured and analyzed during health surveillance inspections in the period from 2006 to 2011. Materials and Methods: Descriptive study analyzing parameters connected with imaging quality of 52 mammography apparatuses inspected at least twice with a one-year interval. Results: Amongst the 16 analyzed parameters, 7 presented more than 70% of conformity, namely: compression paddle pressure intensity (85.1%), films development (72.7%), film response (72.7%), low contrast fine detail (92.2%), tumor mass visualization (76.5%), absence of image artifacts (94.1%), mammography-specific developers availability (88.2%). On the other hand, relevant parameters were below 50% conformity, namely: monthly image quality control testing (28.8%) and high contrast details with respect to microcalcifications visualization (47.1%). Conclusion: The analysis revealed critical situations in terms of compliance with the health surveillance standards. Priority should be given to those mammography apparatuses that remained non-compliant at the second inspection performed within the one-year interval. .

Objetivo: Avaliar a evolução da qualidade da imagem de mamógrafos localizados no Estado do Rio de Janeiro, de 2006 a 2011, com base em parâmetros medidos e observados durante inspeções sanitárias. Materiais e Métodos: Estudo descritivo sobre a evolução de parâmetros que condicionam a qualidade da imagem focalizou 52 mamógrafos, inspecionados no mínimo duas vezes, com intervalo de um ano. Resultados: Dos 16 parâmetros avaliados, 7 apresentaram mais de 70% de conformidade: força do dispositivo de compressão (85,1%), processamento dos filmes (72,7%), resposta do filme do serviço (72,7%), detalhes lineares de baixo contraste (92,2%), visualização de massas tumorais (76,5%), ausência de artefatos de imagem (94,1%), existência de processadoras específicas para mamografia (88,2%). Importantes parâmetros apresentaram-se abaixo de 50% de conformidade: realização de testes mensais da qualidade de imagem pelo estabelecimento (28,8%) e detalhes de alto contraste, que dizem respeito à visualização de microcalcificações (47,1%). Conclusão: A análise revelou situações críticas da atuação da vigilância sanitária, cuja prioridade deveria ser dirigida aos estacionários, ou seja, os mamógrafos que permaneceram na situação de não conformidade nas inspeções realizadas com intervalo de um ano. .

Theoretical and simulation studies on voltage-gated sodium channels

Voltage-gated sodium (Nav) channels are indispensable membrane elements for the generation and propagation of electric signals in excitable cells. The successes in the crystallographic studies on prokaryotic Nav channels in recent years greatly promote the mechanistic investigation of these proteins and their eukaryotic counterparts. In this paper, we mainly review the progress in computational studies, especially the simulation studies, on these proteins in the past years.

Voltage Regulation of Connexin Channel Conductance

Voltage is an important parameter that regulates the conductance of both intercellular and plasma membrane channels (undocked hemichannels) formed by the 21 members of the mammalian connexin gene family. Connexin channels display two forms of voltage-dependence, rectification of ionic currents and voltage-dependent gating. Ionic rectification results either from asymmetries in the distribution of fixed charges due to heterotypic pairing of different hemichannels, or by channel block, arising from differences in the concentrations of divalent cations on opposite sides of the junctional plaque. This rectification likely underpins the electrical rectification observed in some electrical synapses. Both intercellular and undocked hemichannels also display two distinct forms of voltage-dependent gating, termed Vj (fast)-gating and loop (slow)-gating. This review summarizes our current understanding of the molecular determinants and mechanisms underlying these conformational changes derived from experimental, molecular-genetic, structural, and computational approaches.

Tuberculosis in renal transplant patients: The experience of a single center in Medellín-Colombia, 2005-2013 / Tuberculose em pacientes transplantados renais: experiência de um único centro em Medellín-Colômbia, 2005-2013

Introduction: Tuberculosis is a common opportunistic infection in renal transplant patients. Objective: To obtain a clinical and laboratory description of transplant patients diagnosed with tuberculosis and their response to treatment during a period ranging from 2005 to 2013 at the Pablo Tobón Uribe Hospital. Methods: Retrospective and descriptive study. Results: In 641 renal transplants, tuberculosis was confirmed in 12 cases. Of these, 25% had a history of acute rejection, and 50% had creatinine levels greater than 1.5 mg/dl prior to infection. The disease typically presented as pulmonary (50%) and disseminated (33.3%). The first phase of treatment consisted of 3 months of HZRE (isoniazid, pyrazinamide, rifampicin and ethambutol) in 75% of the cases and HZME (isoniazid, pyrazinamide, moxifloxacin and ethambutol) in 25% of the cases. During the second phase of the treatment, 75% of the cases received isoniazid and rifampicin, and 25% of the cases received isoniazid and ethambutol. The length of treatment varied between 6 and 18 months. In 41.7% of patients, hepatotoxicity was associated with the beginning of anti-tuberculosis therapy. During a year-long follow-up, renal function remained stable, and the mortality rate was 16.7%. Conclusion: Tuberculosis in the renal transplant population studied caused diverse nonspecific symptoms. Pulmonary and disseminated tuberculosis were the most frequent forms and required prolonged treatment. Antituberculosis medications had a high toxicity and mortality. This infection must be considered when patients present with a febrile syndrome of unknown origin, especially during the first year after renal transplant. .

Introdução: A tuberculose é uma infecção oportunista comum em pacientes transplantados renais. Objetivo: Oferecer uma descrição clínica e laboratorial de pacientes transplantados com diagnóstico de tuberculose e sua resposta ao tratamento durante o período entre 2005 e 2013 no Hospital Pablo Tobón Uribe. Métodos: Estudo retrospectivo descritivo. Resultados: Em 641 transplantes renais, a tuberculose foi confirmada em 12 pacientes. Destes, 25% tinham histórico de rejeição aguda e 50% apresentaram níveis de creatinina superiores a 1,5 mg/dl antes da infecção. A patologia geralmente se apresentava como pulmonar (50%) e disseminada (33,3%). A primeira fase do tratamento consistiu de três meses de HZRE (isoniazida, pirazinamida, rifampicina e etambutol) em 75% dos casos e HZME (isoniazida, pirazinamida, moxifloxacina e etambutol) em 25% dos pacientes. Durante a segunda fase do tratamento, 75% dos pacientes receberam isoniazida e rifampicina e 25% isoniazida e etambutol. A duração do tratamento variou entre seis e 18 meses. Em 41,7% dos pacientes, hepatotoxicidade foi associada ao início do tratamento da tuberculose. Durante o seguimento de um ano a função renal manteve-se estável e a taxa de mortalidade foi de 16,7%. Conclusão: A tuberculose foi responsável por diversos sintomas inespecíficos na população de transplantados renais estudada. Tuberculose pulmonar e disseminada foram as formas mais frequentes de acometimento e necessitaram de tratamento prolongado. Medicamentos contra a tuberculose apresentaram alta toxicidade e mortalidade. Esta infecção deve ser considerada quando o paciente apresenta síndrome febril de origem desconhecida, especialmente durante o primeiro ano após o transplante renal. .

Chlorogenic acid alters the voltage-gated potassium channel currents of trigeminal ganglion neurons / 国际口腔科学杂志·英文版

Chlorogenic acid (5-caffeoylquinic acid, CGA) is a phenolic compound that is found ubiquitously in plants, fruits and vegetables and is formed via the esterification of caffeic acid and quinic acid. In addition to its notable biological functions against cardiovascular diseases, type-2 diabetes and inflammatory conditions, CGA was recently hypothesized to be an alternative for the treatment of neurological diseases such as Alzheimer's disease and neuropathic pain disorders. However, its mechanism of action is unclear. Voltage-gated potassium channel (Kv) is a crucial factor in the electro-physiological processes of sensory neurons. Kv has also been identified as a potential therapeutic target for inflammation and neuropathic pain disorders. In this study, we analysed the effects of CGA on the two main subtypes of Kv in trigeminal ganglion neurons, namely, the IK,A and IK,V channels. Trigeminal ganglion (TRG) neurons were acutely disassociated from the rat TRG, and two different doses of CGA (0.2 and 1 mmol⋅L(-1)) were applied to the cells. Whole-cell patch-clamp recordings were performed to observe alterations in the activation and inactivation properties of the IK,A and IK,V channels. The results demonstrated that 0.2 mmol⋅L(-1) CGA decreased the peak current density of IK,A. Both 0.2 mmol⋅L(-1) and 1 mmol⋅L(-1) CGA also caused a significant reduction in the activation and inactivation thresholds of IK,A and IK,V. CGA exhibited a strong effect on the activation and inactivation velocities of IK,A and IK,V. These findings provide novel evidence explaining the biological effects of CGA, especially regarding its neurological effects.

Modulation of non-ion channel proteins by membrane potential / 中南大学学报(医学版)

The different concentration of specific ion species and the electrodiffusion of the ions down their electrochemical gradient generate transmembrane potential. The regulation of membrane potential for the function of numerous membrane proteins such as ion channels, transporters, pumps and enzymes plays primary role in the conversion of extracellular electric stimulation into a sequence of intracellular biochemical signals. Some ion channels regulated by membrane potential are well known, and the membrane non-ion channels protein is also modulated physiologically by membrane potential.

Inhibitory effects of blockage of intermediate conductance Ca(2+)-activated K (+) channels on proliferation of hepatocellular carcinoma cells / 华中科技大学学报（医学）（英德文版）

The roles of intermediate conductance Ca(2+)-activated K(+) channel (IKCa1) in the pathogenesis of hepatocellular carcinoma (HCC) were investigated. Immunohistochemistry and Western blotting were used to detect the expression of IKCa1 protein in 50 HCC and 20 para-carcinoma tissue samples. Real-time PCR was used to detect the transcription level of IKCa1 mRNA in 13 HCC and 11 para-carcinoma tissue samples. The MTT assay was used to measure the function of IKCa1 in human HCC cell line HepG2 in vitro. TRAM-34, a specific blocker of IKCa1, was used to intervene with the function of IKCa1. As compared with para-carcinoma tissue, an over-expression of IKCa1 protein was detected in HCC tissue samples (P<0.05). The mRNA expression level of IKCa1 in HCC tissues was 2.17 times higher than that in para-carcinoma tissues. The proliferation of HepG2 cells was suppressed by TRAM-34 (0.5, 1.0, 2.0 and 4.0 μmol/L) in vitro (P<0.05). Our results suggested that IKCa1 may play a role in the proliferation of human HCC, and IKCa1 blockers may represent a potential therapeutic strategy for HCC.

Involvement of acid-sensing ion channel 1a in functions of cultured human retinal pigment epithelial cells / 华中科技大学学报（医学）（英德文版）

In the retina, pH fluctuations may play an important role in adapting retinal responses to different light intensities and are involved in the fine tuning of visual perception. Acidosis occurs in the subretinal space (SRS) under pathological conditions such as age-related macular degeneration (AMD). Although it is well known that many transporters in the retinal pigment epithelium (RPE) cells can maintain pH homeostasis efficiently, other receptors in RPE may also be involved in sensing acidosis, such as acid-sensing ion channels (ASICs). In this study, we investigated whether ASIC1a was expressed in the RPE cells and whether it was involved in the function of these cells. Real-time RT-PCR and Western blotting were used to analyze the ASIC1a expression in ARPE-19 cells during oxidative stress induced by hydrogen peroxide (H(2)O(2)). Furthermore, inhibition or over-expression of ASIC1a in RPE cells was obtained using inhibitors (amiloride and PCTx1) or by the transfection of cDNA encoding hASIC1a. Cell viability was determined by using the MTT assay. The real-time RT-PCR and Western blotting results showed that both the mRNA and protein of ASIC1a were expressed in RPE cells. Inhibition of ASICs by amiloride in normal RPE cells resulted in cell death, indicating that ASICs play an important physiological role in RPE cells. Furthermore, over-expression of ASIC1a in RPE cells prolonged cell survival under oxidative stress induced by H(2)O(2). In conclusion, ASIC1a is functionally expressed in RPE cells and may play an important role in the physiological function of RPE cells by protecting them from oxidative stress.

[ effects of cell phone electromagnetic fields on the behavior of single ompf nanochannel forming protein: a practical approach]

Widespread of telecommunication systems in recent years, have raised the concerns on the possible danger of cell phone radiations on human body. Thus, the study of the electromagnetic fields on proteins, particularly the membrane nano channel forming proteins is of great importance. These proteins are responsible for keeping certain physic-chemical condition within cells and managing cell communication. Here, the effects of cell phones radiation on the activity of a single nanopore ion channel forming protein, OmpF, have been studied biophysically. Planar lipid bilayers were made based on Montal and Muller technique, and the activity of single OmpF channel reconstituted by electrical shock was recorded and analyzed by means of voltage-clamp technique at 20[degree]C. The planar lipid bilayers were formed from the monolayers made on a 60 micro m diameter aperture in the 20 micro m thick Teflon film that separated two [cis and trans] compartments of the glass chamber. In this practical approach we were able to analyze characteristics of an individual channel at different chemical and physical experimental conditions. The voltage clamp was used to measure the channel's conductance, voltage sensitivity, gating patterns in time scales as low as microseconds in real time. Our results showed that exposure of single voltage dependent channel, OmpF, to EMF of cell phone at high-frequency has a significant influence on the voltage sensitivity, gating properties and substate numbers of the single channel but has no effect on single-channel conductance. Regarding to the relaxation time, the channel also recovers in the millisecond time range when the field is removed. We observed an increase in the voltage sensitivity of the OmpF single channel while it had no effect on the single-channel conductance, which is remained to be further elucidated.

Effect of electroacupuncture on the pathomorphology of the sciatic nerve and the sensitization of P2X₃ receptors in the dorsal root ganglion in rats with chronic constrictive injury / 中国结合医学杂志

<p><b>OBJECTIVE</b>To explore the effect of electroacupuncture (EA) on the pathomorphology of the sciatic nerve and the role of P2X3 receptors in EA analgesia.</p><p><b>METHODS</b>The chronic constriction injury (CCI) model was adopted in this study. A total of 32 rats were randomly divided into four groups: sham CCI, CCI, CCI plus contralateral EA (CCI + conEA) and CCI plus ipsilateral EA (CCI + ipsEA). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured. EA began at day 7 after the CCI operation and was applied to the Zusanli (ST 36) and Yanglingquan acupoints (GB 34). At day 14, the pathomorphologic changes of the operated sciatic nerve were demonstrated by hematoxylin and eosin staining. In addition, dorsal root ganglion (DRG) neurons isolated from rats were examined by electrophysiological recording to determine if the P2X3 receptor agonists, adenosine 5'-triphosphate disodium (ATP) and α,β-methylen-ATP (α,β-meATP) evoked inward currents.</p><p><b>RESULTS</b>Pain thresholds in the CCI group were obviously decreased post CCI surgery (P<0.01). In the EA groups, thermal and mechanical threshold values were increased after the last EA treatment (P<0.05, P<0.01). There was no significant difference in light microscopic examination among the four groups (P>0.05). Current amplitude after application of ATP and α,β-meATP in DRG neurons were much larger in the CCI group compared to those obtained in sham CCI (P<0.05). ATP and α, β-meATP invoked amplitudes in the CCI + EA groups were reduced. There was no signififi cant difference between the CCI + conEA group and the CCI + ipsEA group (P>0.05).</p><p><b>CONCLUSION</b>EA analgesia may be mediated by decreasing the response of P2X3 receptors to the agonists ATP and α,β-meATP in the DRG of rats with CCI. No pathological changes of the sciatic nerve of rats were observed after EA treatment.</p>

Conserved motifs in voltage sensing proteins / 生理学报

This paper was aimed to study conserved motifs of voltage sensing proteins (VSPs) and establish a voltage sensing model. All VSPs were collected from the Uniprot database using a comprehensive keyword search followed by manual curation, and the results indicated that there are only two types of known VSPs, voltage gated ion channels and voltage dependent phosphatases. All the VSPs have a common domain of four helical transmembrane segments (TMS, S1-S4), which constitute the voltage sensing module of the VSPs. The S1 segment was shown to be responsible for membrane targeting and insertion of these proteins, while S2-S4 segments, which can sense membrane potential, for protein properties. Conserved motifs/residues and their functional significance of each TMS were identified using profile-to-profile sequence alignments. Conserved motifs in these four segments are strikingly similar for all VSPs, especially, the conserved motif [RK]-X(2)-R-X(2)-R-X(2)-[RK] was presented in all the S4 segments, with positively charged arginine (R) alternating with two hydrophobic or uncharged residues. Movement of these arginines across the membrane electric field is the core mechanism by which the VSPs detect changes in membrane potential. The negatively charged aspartate (D) in the S3 segment is universally conserved in all the VSPs, suggesting that the aspartate residue may be involved in voltage sensing properties of VSPs as well as the electrostatic interactions with the positively charged residues in the S4 segment, which may enhance the thermodynamic stability of the S4 segments in plasma membrane.

The BK channel: a vital link between cellular calcium and electrical signaling

Large-conductance Ca²⁺-activated K⁺ channels (BK channels) constitute an key physiological link between cellular Ca²⁺ signaling and electrical signaling at the plasma membrane. Thus these channels are critical to the control of action potential firing and neurotransmitter release in several types of neurons, as well as the dynamic control of smooth muscle tone in resistance arteries, airway, and bladder. Recent advances in our understanding of K⁺ channel structure and function have led to new insight toward the molecular mechanisms of opening and closing (gating) of these channels. Here we will focus on mechanisms of BK channel gating by Ca²⁺, transmembrane voltage, and auxiliary subunit proteins.

Exploring the obscure profiles of pharmacological binding sites on voltage-gated sodium channels by BmK neurotoxins

Diverse subtypes of voltage-gated sodium channels (VGSCs) have been found throughout tissues of the brain, muscles and the heart. Neurotoxins extracted from the venom of the Asian scorpion Buthus martensi Karsch (BmK) act as sodium channel-specific modulators and have therefore been widely used to study VGSCs. α-type neurotoxins, named BmK I, BmK αIV and BmK abT, bind to receptor site-3 on VGSCs and can strongly prolong the inactivation phase of VGSCs. In contrast, β-type neurotoxins, named BmK AS, BmK AS-1, BmK IT and BmK IT2, occupy receptor site-4 on VGSCs and can suppress peak currents and hyperpolarize the activation kinetics of sodium channels. Accumulating evidence from binding assays of scorpion neurotoxins on VGSCs, however, indicate that pharmacological sensitivity of VGSC subtypes to different modulators is much more complex than that suggested by the simple α-type and β-type neurotoxin distinction. Exploring the mechanisms of possible dynamic interactions between site 3-/4-specific modulators and region- and/or species-specific subtypes of VGSCs would therefore greatly expand our understanding of the physiological and pharmacological properties of diverse VGSCs. In this review, we discuss the pharmacological and structural diversity of VGSCs as revealed by studies exploring the binding properties and cross-competitive binding of site 3- or site 4-specific modulators in VGSC subtypes in synaptosomes from distinct tissues of diverse species.

A method of acutely isolating rat dorsal root ganglion neurons for patch-clamp study of single-channel / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To establish a method of acutely isolating dorsal root ganglion (DRG) neurons for patch clamp study of single-channel.</p><p><b>METHODS</b>DRG neurons of rats were acutely isolated by enzymatic digestion and mechanical blowing.</p><p><b>RESULTS</b>The acutely isolated DRG cells were easy to form the higher sealing resistance (> 5G Omega), which lowered noise level, so that pA-level single channel currents could be recorded.</p><p><b>CONCLUSION</b>The acutely isolated DRG neurons in this study are an ideal for patch-clamp study of single-channel.</p>

Potassium channel openers exhibit cross-tolerance with morphine in two experimental models of pain / Los abridores de canales de potasio exhiben tolerancia cruzada con la morfina en dos modelos experimentales de dolor

OBJECTIVE: The study was performed to assess the effect of potassium channel openers on morphine tolerance and vice-versa. METHODS: Swiss albino mice of either gender weighing between 25-30 g were used for the study. The study assesses the effect of potassium channel openers (cromakalim, diazoxide and minoxidil) on morphine tolerance and vice-versa, using formalin and tail-flick tests. RESULTS: The antinociceptive effect of cromakalim and minoxidil was significantly reduced when administered to morphine-tolerant mice, in both the behavioural tests. However, reduced analgesic effect of diazoxide was observed on morphine-tolerance in the formalin test but not in the tail-flick test. Tolerance was observed when morphine was administered to animals chronically treated with any of the potassium channel openers. The same effect was observed when morphine was injected into a group treated with a combination of morphine and any of the potassium channel openers. CONCLUSIONS: This study, therefore, suggests that both morphine and potassium channel openers are cross-tolerant. However, such interaction occurs at the level of potassium channels rather than at the level of receptors.

OBJETIVO: El estudio fue realizado para evaluar el efecto de los abridores de canales de potasio en la tolerancia a la morfina, y viceversa. MÉTODOS: Para el estudio, se usaron ratones albinos suizos de ambos sexos que pesaban entre 25-30 g. El estudio evalúa el efecto de los abridores de canales de potasio (cromacalina, diazóxido y minoxidil) en la tolerancia a la morfina, y viceversa, usando la prueba de la sacudida de la cola y la prueba de la formalina. RESULTADOS: El efecto antinociceptivo de la cromacalina y el minoxidil fue significativamente reducido cuando se le administró a los ratones tolerantes a la morfina, en ambas pruebas conductuales. Sin embargo, se observó un efecto analgésico reducido de diazóxido sobre la tolerancia a la morfina en la prueba de la formalina, pero no en la prueba de la sacudida de la cola. Se observó tolerancia al administrar morfina a animales crónicamente tratados con cualquiera de los abridores de canales de potasio. El mismo efecto fue observado cuando se inyectó la morfina al grupo tratado con una combinación de morfina y cualquiera de los abridores de canales de potasio. CONCLUSIONES: Por consiguiente, este estudio sugiere que tanto la morfina como los abridores de canales de potasio son tolerantes cruzados. Sin embargo, tal interacción ocurre a nivel de los canales de potasio más bien que a nivel de los receptores.