Permeable Channels Research Articles

Functional coupling between Piezo1 and TRPM4 influences the electrical activity of HL-1 atrial myocytes.

The transient receptor potential melastatin 4 (TRPM4) channel contributes extensively to cardiac electrical activity, especially cardiomyocyte action potential formation. Mechanical stretch can induce changes in heart rate and rhythm, and the mechanosensitive channel Piezo1 is expressed in many cell types within the myocardium. Our previous study showed that TRPM4 and Piezo1 are closely co-localized in the t-tubules of ventricular cardiomyocytes and contribute to the Ca2+-dependent signalling cascade that underlies hypertrophy in response to mechanical pressure overload. However, there was no direct evidence showing that Piezo1 activation was related to TRPM4 activation in situ. In the present study, we employed the HL-1mouse atrial myocyte-like cell line as an in vitro model to investigate whether Piezo1-TRPM4 coupling can affect action potential properties. We used the small molecule Piezo1 agonist, Yoda1, as a surrogate for mechanical stretch to activate Piezo1 and detected the action potential changes in HL-1 cells using FluoVolt, a fluorescent voltage sensitive dye. Our results demonstrate that Yoda1-induced activation of Piezo1 changes the action potential frequency in HL-1 cells. This change in action potential frequency is reduced by Piezo1 knockdown using small intefering RNA. Importantly knockdown or pharmacological inhibition of TRPM4significantly affected the degree to which Yoda1-evoked Piezo1 activation influenced action potential frequency. Thus, the present study provides in vitro evidence of a functional coupling between Piezo1 and TRPM4 in a cardiomyocyte-like cell line. The coupling of a mechanosensitive Ca2+ permeable channel and a Ca2+-activated TRP channel probably represents a ubiquitous model for the role of TRP channels in mechanosensory transduction. KEY POINTS: The transient receptor potential melastatin 4 (TRPM4) and Piezo1 channels have been confirmed to contribute to the Ca2+-dependent signalling cascade that underlies cardiac hypertrophy in response to mechanical pressure overload. However, there was no direct evidence showing that Piezo1 activation was related to TRPM4 activation in situ. We employed the HL-1mouse atrial myocyte-like cell line as an in vitro model to investigate the effect of Piezo1-TRPM4 coupling on cardiac electrical properties. The results show that both pharmacological and genetic inhibition of TRPM4significantly affected the degree to which Piezo1 activation influenced action potential frequency in HL-1 cells. Our findings provide in vitro evidence of a functional coupling between Piezo1 and TRPM4 in a cardiomyocyte-like cell line. The coupling of a mechanosensitive Ca2+ permeable channel and a Ca2+-activated TRP channel probably represents a ubiquitous model for the role of TRP channels in mechanosensory transduction in various (patho)physiological processes.

Calcium Influx Pathways in Breast Cancer: Opportunities for Pharmacological Intervention

Numerous cellular processes, including the release of neurotransmitters and the contraction of muscles, are largely triggered and regulated by Ca2+ inflow via Ca2+ permeable ion channels. In addition, Ca2+ influx regulates cellular migration and proliferation, two mechanisms linked to cancer. This study focuses on calcium influx in breast cancer cells and discusses how future drugs for breast cancer therapy may be pharmacological modulators of particular Ca2+ influx channels. Certain breast tumors have altered expression of particular calcium permeable ion channels. Such alterations may occasionally be connected to the prognosis and subtype of breast cancer. These days, models both in vivo and in vitro have assisted in identifying particular Ca2+ channels that are crucial for the growth and invasiveness of of cancerous breast cells. Nonetheless, additional research is still needed to fully understand several features of Ca2+ influx in breast cancer. These include figuring out the processes behind the changed expression and the best treatment plan to target breast cancer cells via particular Ca2+ channels. In the upcoming ten years, research should concentrate on the function of Ca2+ influx in mechanisms other than the migration and proliferation of breast cancer cells.

Pharmacological Therapeutic Potential in Breast Cancer through Calcium Influx Pathways

Numerous cellular processes, including the release of neurotransmitters and the contraction of muscles, are largely triggered and regulated by Ca2+ inflow via Ca2+ permeable ion channels. In addition, Ca2+ influx regulates cellular migration and proliferation, two mechanisms linked to cancer. This study focuses on calcium influx in breast cancer cells and discusses how future drugs for breast cancer therapy may be pharmacological modulators of particular Ca2+ influx channels. Certain breast tumors have altered expression of particular calcium permeable ion channels. Such alterations may occasionally be connected to the prognosis and subtype of breast cancer. These days, models both in vivo and in vitro have assisted in identifying particular Ca2+ channels that are crucial for the growth and invasiveness of cancerous breast cells. Nonetheless, additional research is still needed to fully understand several features of Ca2+ influx in breast cancer. These include figuring out the processes behind the changed expression and the best treatment plan to target breast cancer cells via particular Ca2+ channels. In the upcoming ten years, research should concentrate on the function of Ca2+ influx in mechanisms other than the migration and proliferation of breast cancer cells

A Ca2+ sensor BraCBL1.2 involves in BraCRa-mediated clubroot resistance in Chinese cabbage.

Clubroot disease caused by Plasmodiophora brassicae (P. brassicae) severely threatens the cultivation of Cruciferous plants, especially Chinese cabbage. Recently, resistance genes in plants have been reported to encode for a Ca2+-permeable channel in the plasma membrane, which can mediate the cytosolic Ca2+ increase in plant cells upon pathogen attack. However, the downstream Ca2+ sensor and decoder are still unknown. In this study, we identified the virulent and avirulent P. brassicae isolates (Pbs) of two near isogenic lines, CR 3-2 and CS 3-2, with CR 3-2 harboring clubroot resistant gene BraCRa. The transcriptomic analysis was then conducted with CR 3-2 after inoculating with virulent isolate PbE and avirulent isolate Pb4. From the differentially expressed genes of transcriptomic data, we identified a Ca2+-sensor encoding gene, BraCBL1.2, that was highly induced in CR 3-2 during infection by Pb4 but not by PbE. Moreover, GUS histochemical staining and subcellular localization analysis revealed that BraCBL1.2 was specifically expressed in the root hair cells of Arabidopsis and encoded a putative Ca2+ sensor localized in the plasma membrane. We also developed an assay to investigate the BraCRa-mediated hypersensitive response (HR) in tobacco leaves. The results suggest that BraCBL1.2 is involved in the BraCRa-mediated plant ETI immune response against P. brassicae. In addition, we verified that overexpression of BraCBL1.2 enhanced clubroot resistance in Arabidopsis. Collectively, our data identified the involvement of a Ca2+ sensor in BraCRa-mediated clubroot resistance in Chinese cabbage, providing a theoretical basis for further research on the resistance of Chinese cabbage to P. brassicae.

Effect of sand production on physical properties and fracturing development of gas hydrate reservoir

Offshore gas hydrates are being focused on as an unconventional energy source. The susceptibility of marine hydrate reservoirs to sand emergence makes them unsuitable for long-term exploitation. This research delves into the particle-transport law in hydrate reservoirs, revealing that sand blockage hinders long-term exploitation, and proposes a reservoir modification strategy to establish high-permeability channels, thereby enhancing production. After 110 days of mining, the range of porosity and permeability below the initial value was approximately 8.5 m. The study further optimizes reservoir modification parameters under sand blockage, suggesting that a balance between fracture and reservoir blockage can be achieved with a fracture half-length of 20 m, leading to increased production. It also highlights that the slow decomposition of blocked hydrate and the accumulation of decomposed methane gas in the upper part of the reservoir can be leveraged to increase production by providing a high permeability channel for free gas, concluding that maintaining long-term high permeability is crucial for hydrate reservoir fractures.

Discovery of flavone-derivatives as the new skeleton of transient receptor potential vanilloid 3 channel antagonists

Transient receptor potential vanilloid 3 (TRPV3) channel is a temperature-sensitive and Ca2+-permeable nonselective cation channel, which is abundantly expressed in skin keratinocyte and plays an important role in skin homeostasis and repair. However, only a few TRPV3 inhibitors were reported. Few selective and potent modulators of the TRPV3 channel have hindered the progress of the investigation and clinical application. TRPV3 channel research still faces challenges and requires the new inhibitors. Flavonoids are a kind of natural compounds with various biological and pharmacological activities including anti-inflammatory and anti allergic effects, which is associated with some physiological effects mediated by TRPV3 channel. Herein, our group designed and synthesized a range of flavone derivatives, and investigated their inhibitory properties on the human TRPV3 channel by electrophysiology technique. Then, we identified a new potent TRPV3 antagonist 2d with IC50 of 0.62 μM. It also showed good selectivity on TRPV1, TRPV4, TRPA1 and TRPM8.

NaX Channel Is a Physiological [Na+] Detector in Oxytocin- and Vasopressin-Releasing Magnocellular Neurosecretory Cells of the Rat Supraoptic Nucleus.

The Scn7A gene encodes NaX, an atypical noninactivating Na+ channel, whose expression in sensory circumventricular organs is essential to maintain homeostatic responses for body fluid balance. However, NaX has also been detected in homeostatic effector neurons, such as vasopressin (VP)-releasing magnocellular neurosecretory cells (MNCVP) that secrete VP (antidiuretic hormone) into the bloodstream in response to hypertonicity and hypernatremia. Yet, the physiological relevance of NaX expression in these effector cells remains unclear. Here, we show that rat MNCVP in males and females is depolarized and excited in proportion with isosmotic increases in [Na+]. These responses were caused by an inward current resulting from a cell-autonomous increase in Na+ conductance. The Na+-evoked current was unaffected by blockers of other Na+-permeable ion channels but was significantly reduced by shRNA-mediated knockdown of Scn7A expression. Furthermore, reducing the density of NaX channels selectively impaired the activation of MNCVP by systemic hypernatremia without affecting their responsiveness to hypertonicity in vivo These results identify NaX as a physiological Na+ sensor, whose expression in MNCVP contributes to the generation of homeostatic responses to hypernatremia.SIGNIFICANCE STATEMENT In this study, we provide the first direct evidence showing that the sodium-sensing channel encoded by the Scn7A gene (NaX) mediates cell-autonomous sodium detection by MNCs in the low millimolar range and that selectively reducing the expression of these channels in MNCs impairs their activation in response to a physiologically relevant sodium stimulus in vitro and in vivo These data reveal that NaX operates as a sodium sensor in these cells and that the endogenous sensory properties of osmoregulatory effector neurons contribute to their homeostatic activation in vivo.

Nanoscale one-dimensional close packing of interfacial alkali ions driven by water-mediated attraction.

The permeability and selectivity of biological and artificial ion channels correlate with the specific hydration structure of single ions. However, fundamental understanding of the effect of ion-ion interaction remains elusive. Here, via non-contact atomic force microscopy measurements, we demonstrate that hydrated alkali metal cations (Na+ and K+) at charged surfaces could come into close contact with each other through partial dehydration and water rearrangement processes, forming one-dimensional chain structures. We prove that the interplay at the nanoscale between the water-ion and water-water interaction can lead to an effective ion-ion attraction overcoming the ionic Coulomb repulsion. The tendency for different ions to become closely packed follows the sequence K+ > Na+ > Li+, which is attributed to their different dehydration energies and charge densities. This work highlights the key role of water molecules in prompting close packing and concerted movement of ions at charged surfaces, which may provide new insights into the mechanism of ion transport under atomic confinement.

Numerical analysis of electromagnetic trihybrid nanofluid flow in a convectively heated permeable channel

Numerical analysis of electromagnetic trihybrid nanofluid flow in a convectively heated permeable channel

Insight of boundary layer structure with heat transfer through a diverging porous channel in Darcy-Forchheimer porous material with suction/injection: A study of separation control

Separation control and formation of boundary layer Newtonian flow in a diverging perme-able channel in Darcy-Forchheimer porous material having suction/injection are discussed. Self-similar equations from governing equations are acquired and existence conditions for boundary layer structure are derived using nature of velocity gradient inside boundary layer. It reveals that if sum of Darcy permeability parameter and twice of Forchheimer parameter exceeds 2, then the boundary layer flow always exists with all type of mass suction/injection and even without suction/injection. Also, if mass suction parameter goes beyond 22, then there is no matter what are the values of Darcy permeability parameter and Forchheimer pa-rameter, a boundary layer exists inside the divergent channel. In addition, obtained numerical solutions are exhibited graphically. It reveals that thicknesses of velocity and thermal bound-ary layers reduce with Darcy and non-Darcy resistances of porous medium and fluid tempera-ture also diminishes. The velocity and temperature reduce with increment of mass suction and contrary results are found for mass injection.

Signalling mechanisms and agricultural applications of (Z)-3-hexenyl butyrate-mediated stomatal closure.

Biotic and abiotic stresses can severely limit crop productivity. In response to drought, plants close stomata to prevent water loss. Furthermore, stomata are the main entry point for several pathogens. Therefore, the development of natural products to control stomata closure can be considered a sustainable strategy to cope with stresses in agriculture. Plants respond to different stresses by releasing volatile organic compounds. Green leaf volatiles, which are commonly produced across different plant species after tissue damage, comprise an important group within volatile organic compounds. Among them, (Z)-3-hexenyl butyrate (HB) was described as a natural inducer of stomatal closure, playing an important role in stomatal immunity, although its mechanism of action is still unknown. Through different genetic, pharmacological, and biochemical approaches, we here uncover that HB perception initiates various defence signalling events, such as activation of Ca2+ permeable channels, mitogen-activated protein kinases, and production of Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mediated reactive oxygen species. Furthermore, HB-mediated stomata closure was found to be independent of abscisic acid biosynthesis and signalling. Additionally, exogenous treatments with HB alleviate water stress and improve fruit productivity in tomato plants. The efficacy of HB was also tested under open field conditions, leading to enhanced resistance against Phytophthora spp. and Pseudomonas syringae infection in potato and tomato plants, respectively. Taken together, our results provide insights into the HB signalling transduction pathway, confirming its role in stomatal closure and plant immune system activation, and propose HB as a new phytoprotectant for the sustainable control of biotic and abiotic stresses in agriculture.

Inhibition of Ca2+-permeable TRPV3 and inflammatory cytokine release by honokiol and magnolol in human epidermal keratinocytes

Transient receptor potential vanilloid-3 (TRPV3) ion channels are prominently expressed in keratinocytes, playing a vital role in skin functions. Honokiol and magnolol (H&M) the primary bioactive constituents in Magnolia officinalis extract, demonstrate anti-inflammatory and skin-protective properties. Nevertheless, the underlying mechanism regarding their effect on Ca2+-permeable ion channels remain unclear. Our purpose in this study is to investigate the effect of H&M on TRPV3 and cytokine release in normal human epidermal keratinocytes (NHEKs), including its gain-of-function (GOF) mutants (G573S and G573C) associated with Olmstead syndrome. We performed whole-cell patch-clamp, fura-2 spectrofluorimetry to investigate channels activity, CCK-8 assay to analyze cell death and enzyme-linked immunosorbent assay to assess the cytokine release from NHEKs. H&M inhibited the TRPV3 current (ITRPV3) and cytosolic calcium increase in NHEKs, HEK293T cells overexpressing hTRPV3 and its GOF mutants. Moreover, the release of pro-inflammatory cytokines (interleukin-6 and -8) from keratinocytes stimulated by TRPV3 agonist was effectively suppressed by H&M. Our findings provide insights into the mechanism underlying the anti-inflammatory effects of H&M, highlighting their potential in treating skin diseases.

Praziquantel activates a native cation current in Schistosoma mansoni

IntroductionPraziquantel (PZQ), an anthelmintic drug discovered in the 1970s, is still used to treat schistosomiasis and various other infections caused by parasitic flatworms. PZQ causes a triad of phenotypic effects on schistosome worms – rapid depolarization, muscle contraction, and damage throughout the worm tegument. The molecular target mediating these effects has been intimated as a Ca2+-permeable ion channel, but native currents evoked by PZQ have not been reported in any schistosome cell type. The properties of the endogenous PZQ activated conductance therefore remain unknown. MethodsHere, invasive electrophysiology was used to probe for responses to PZQ from different locales in a living schistosome worm.Results and discussionNo direct response was seen in tegument-derived vesicles, or from the sub-tegumental muscle layer despite the presence of voltage-operated currents. However, PZQ rapidly triggered a sustained, non-selective cation current in recordings from neuronal tissue, targeting both the anterior ganglion and the main longitudinal nerve cord. The biophysical signature of this PZQ-evoked current resolved at single channel resolution matched that of a transient receptor potential ion channel named TRPMPZQ, recently proposed as the molecular target of PZQ. The endogenous PZQ-evoked current was also inhibited by a validated TRPMPZQ antagonist. PZQ therefore is a neuroactive anthelmintic, causing a sustained depolarization through ion channels with the characteristics of TRPMPZQ.

Oxidative stress–mediated proapoptosis signaling: A novel theory on the mechanism underlying the pathogenesis of burning mouth syndrome

BackgroundBurning mouth syndrome (BMS) is a chronic oral pain disorder characterized by a generalized burning sensation in the oral mucosa without apparent medical or dental causes. Despite various hypotheses proposed to explain BMS pathogenesis, a clear understanding of the cellular-level events and associated histologic and molecular findings is lacking. Advancing our understanding of BMS pathogenesis could facilitate the development of more targeted therapeutic interventions. Types of Studies ReviewedThe authors conducted an extensive literature search and review of cellular mechanisms, focusing on evidence-based data that support a comprehensive hypothesis for BMS pathogenesis. The authors explored novel and detailed mechanisms that may account for the characteristic features of BMS. ResultsThe authors proposed that BMS symptoms arise from the uncontrolled activation of proapoptotic transmembrane calcium permeable channels expressed in intraoral mucosal nerve fibers. Elevated levels of reactive oxygen species or dysfunctional antiapoptosis pathways may lead to uncontrolled oxidative stress–mediated apoptosis signaling, resulting in upregulation of transmembrane transient receptor potential vanilloid type 1 and P2X 3 calcium channels in nociceptive fibers. Activation of these channels can cause nerve terminal depolarization, leading to generation of action potentials that are centrally interpreted as pain. Conclusions and Practical ImplicationsThe authors present a novel hypothesis for BMS pathogenesis, highlighting the role of proapoptotic transmembrane calcium permeable channels and oxidative stress–mediated apoptosis signaling in the development of BMS symptoms. Understanding these underlying mechanisms could provide new insights into the development of targeted therapeutic interventions for BMS. Additional research is warranted to validate this hypothesis and explore potential avenues for effective management of BMS.

Thermal study of Darcy–Forchheimer hybrid nanofluid flow inside a permeable channel by VIM: features of heating source and magnetic field

Thermal study of Darcy–Forchheimer hybrid nanofluid flow inside a permeable channel by VIM: features of heating source and magnetic field

Abstract 18731: Connexin 43 Hemichannels Contribution to Ischemia-Reperfusion-Induced Hyperpermeability

Introduction: Ischemia-reperfusion (I-R) injury is a significant complication in vascular surgery or organ transplantation. I-R injury involves intracellular Ca2+ overload, nitric oxide (NO), oxidative stress. I-R injury increases endothelial vascular hyperpermeability leading to tissue edema and damage mediated by endothelial Ca2+ increase. The role of Ca2+ permeable channels in I-R is not defined. Connexin (Cx) proteins form hemichannels, allowing the exchange of molecules between intracellular and extracellular spaces. The Cx43 isoform is highly expressed in endothelial cells (EC). Endothelial Ca2+ increase promotes NO-dependent Cx43 S-nitrosylation. However, whether Cx43 hemichannels are involved in I-R-induced hyperpermeability is unknown. Hypothesis: VEGF-induced hyperpermeability causes increased NO-mediated Cx43 S-nitrosylation and opening of endothelial Cx43 hemichannels, leading to Ca2+ entry and exacerbating reperfusion damage. Methods: We used VEGF as I-R related pro-inflammatory agonist. Using primary cultures of mesenteric endothelial cells, we tested Cx43 hemichannel activity by ethidium uptake and Ca2+ influx with Fluo-4 indicator. We evaluated hyperpermeability in vitro and in vivo Results: Results indicate that VEGF stimulation increased hemichannel activity in EC, associated with a rapid rise of Ca2+ influx. Both hemichannel activation and Ca2+ increase were abolished by treatment with specific Cx43 blocker (Gap19) or blocking NO production with NG-monomethyl-L-arginine (LNMMA). Cx43 inhibition blunted VEGF-induced hyperpermeability both in vitro in primary EC culture and in vivo mouse mesenteric vascular bed. To further understand the participation of NO-mediated S-nitrosylation in the VEGF-induced hyperpermeability, we replaced cysteine 271 by serine to create a Cx43C271S mouse that fails to cause S-nitrosylation of Cx43. We demonstrated that this knockin mouse exhibits a decrease in VEGF-stimulated hyperpermeability in vivo. Conclusions: These results indicate that Cx43 hemichannels activation is critical to VEGF (I-R inflammatory environment)-induced hyperpermeability and the S-nitrosylated Cx43 is a key regulator in I-R damage. AHA support: # 932684 and #23DIVSUP1054931

Comparative analysis of nanofluid flows in the dilating squeezing porous channel with thermal jump and slip conditions

This study investigates the behavior of the mono and hybrid nanofluid flows in an absorbent dilating/squeezing channel influenced by a magnetic field. The mono nanofluid is molded by inserting iron oxide (Fe3O4) nanoparticles into the blood (base fluid) and the targeted hybrid magnetic nanofluid is formed when the Cobalt iron oxide (CoFe2O4) nanoparticles are added into Fe3O4/blood nanofluid mixture. For a permeable channel, the slip boundary along with the thermal jump condition is imposed. The process for heat transfer is examined considering the Cattaneo-Christov heat flux. Throughout the analysis, platelet-shaped nanoparticles are used. The Tiwari and Das (single phase) nanoliquid flow model is adopted here. The ordinary differential equations (ODEs) are accomplished via similarity transformations and are numerically assessed using the bvp4c software. Moreover, the consequences of the resulting pertinent parameters on the streamlines, temperature, and velocity distributions are scrutinized using graphical representations. It is observed that the surface drag on the wall is weaker for the dilating/injection case as compared to the squeezing/suction scenario. Streamlines show how a suitable magnetic field may be used to regulate medicine distribution in the blood flow. An innovative mass-based model comprising mono and hybrid nanofluid flow models is discussed. A comparison of heat transfer between both is undertaken. The results indicate that increasing the magnetic parameter leads to an enhancement in heat transfer rate when the upper and lower walls are dilated with wall injection Conversely, if the upper and lower walls are squeezed with wall suction the heat transfer rate decreases. The novelty lies in the consideration of both types of models and making a comparison of these.

AtFH5-labeled secretory vesicles-dependent calcium oscillation drives exocytosis and stepwise bulge during pollen germination

Pollen germination is an essential step for delivering sperm cells to the embryo sac for double fertilization inflowering plants. The cytosolic Ca2+ concentration ([Ca2+]cyt) and vesicle dynamics are critical for pollengermination, but their potential correlation in pollen grains is not fully understood. Here, we report that [Ca2+]cyt oscillates periodically at the prospective germination sites during pollen germination. The [Ca2+]cyt is mainly from extracellular Ca2+ ([Ca2+]ext) influx, which implicates the Ca2+-permeable ion channel cyclic nucleotide-gated channel 18 (CNGC18). The [Ca2+]cyt oscillations spatiotemporally correlate with the accumulation of secretory vesicles labeled by a formin protein AtFH5, and disruption of vesicle accumulation inhibits the [Ca2+]cyt oscillations. In turn, the [Ca2+]cyt oscillations promote exocytosis, which leads to stepwise cell extension during pollen germination. Together, these data provide a timeline of vesicle dynamics, calcium oscillation, and exocytosis during pollen germination and highlight the importance of the correlation of these events for pollen germination.

Magnetohydrodynamic Couette flow of alumina–water nanofluid over a deformable porous channel under uniform transverse magnetic field with entropy optimisation

The present study is concerned about magnetohydrodynamic Couette flow of nanofluid with entropy analysis in the presence of injection and suction over a deformable permeable channel containing nanoparticles of alumina (Al2O3). The influences of non-linear thermal radiation and activation energy are considered. The leading partial differential equations are simplified to non-linear ordinary differential equations by applying appropriate similarity transformation. The simplified governing equations are solved by utilising MATLAB bvp4c finite difference technique. Here, we observed the behaviour of various physical parameters on solid displacement, temperature, velocity, concentration, entropy generation, Bejan number and skin friction. Observation reflects that drag parameter enhances solid displacement, while reduces fluid velocity, and a significant behaviour is seen in skin friction. Radiation parameter and chemical reaction parameter diminish the fluid temperature and concentration, respectively. Moreover, volume fraction parameter reflects some significant behaviour for entropy generation number and Bejan number. Rate of heat transfer enhances due to the raising of radiation parameter. Fluid flow through a deformable porous regime established by biological applications such as study on articular cartilage, artery walls, skin, soft tissue and so on.

Readiness of nociceptor cell bodies to generate spontaneous activity results from background activity of diverse ion channels and high input resistance.

Nociceptor cell bodies generate "spontaneous" discharge that can promote ongoing pain in persistent pain conditions. Little is known about the underlying mechanisms. Recordings from nociceptor cell bodies (somata) dissociated from rodent and human dorsal root ganglia have shown that previous pain in vivo is associated with low-frequency discharge controlled by irregular depolarizing spontaneous fluctuations of membrane potential (DSFs), likely produced by transient inward currents across the somal input resistance. Using mouse nociceptors, we show that DSFs are associated with high somal input resistance over a wide range of membrane potentials, including depolarized levels where DSFs approach action potential (AP) threshold. Input resistance and both the amplitude and frequency of DSFs were increased in neurons exhibiting spontaneous activity. Ion substitution experiments indicated that the depolarizing phase of DSFs is generated by spontaneous opening of channels permeable to Na + or Ca 2+ and that Ca 2+ -permeable channels are especially important for larger DSFs. Partial reduction of the amplitude or frequency of DSFs by perfusion of pharmacological inhibitors indicated small but significant contributions from Nav1.7, Nav1.8, TRPV1, TRPA1, TRPM4, and N-type Ca 2+ channels. Less specific blockers suggested a contribution from NALCN channels, and global knockout suggested a role for Nav1.9. The combination of high somal input resistance plus background activity of diverse ion channels permeable to Na + or Ca 2+ produces DSFs that are poised to reach AP threshold if resting membrane potential depolarizes, AP threshold decreases, or DSFs become enhanced-all of which can occur under painful neuropathic and inflammatory conditions.