Search

The land surface temperature (LST) is an important indicator reflecting the ecological environment condition. As a sensitive area to climate change, mastering the spatial and temporal changes of summer LST in the Bosten Lake basin (BLB) helps gain insight into the evolution of the thermal environment in the Bosten Lake basin and for long-term monitoring of the basic ecological changes in the basin. Based on MOD11A1 data from 2005 to 2020, this paper investigates the diurnal LST spatiotemporal series variation and its influencing factors in the Bosten Lake basin by using surface temperature class classification, trending analysis, the Hurst index, and geographic probes. The results show that (1) the wetland grasslands in and around the Bayinbruck steppe in the northwestern part of the study area exhibit a heat island effect during the day, while the opposite is true at night. In terms of temporal changes, LST changes in the BLB fluctuate widely, having a general rising and then decreasing trend. (2) The decreasing trend of LST from 2005 to 2020 is significant during the daytime and vice versa at night, and the change at night is greater than during the day. The areas with significantly higher diurnal LST in the future have all expanded compared to the area occupied by them now, with an overall trend of a steady increase. (3) The dominant factor of LST variation has the strongest explanatory power when altitude and NDVI are combined during the daytime and the strongest explanatory power when NPP and temperature are combined at night.

Thiamethoxam (TMX) has been registered for use on a wide range of crops due to its broad pest spectrum, high efficiency and versatile application methods. However, there is limited literature evaluating the residue behaviors of TMX applied through root irrigation. In this study, the uptake and translocation of TMX, its degradation to clothianidin (CLO) and risk assessment of TMX application in a tomato plant ecosystem were evaluated. TMX applied through root irrigation was transferable within the tomato plant, including stems, leaves and fruit at different heights. TMX concentration in the four sections of stems was ordered as Clower > Cmid > Cupper > Ctop, while in the leaves the order was the opposite and the top had the highest concentration. The degradation product CLO was detected in the tomato plant, and the concentration order was Cleaf > Croot > Cstem > Ctomato. In the leaves, the concentrations of CLO were even higher than those of TMX. The translocation factor (TF) in the same section generally followed the order of TFleaf > TFstem > TFtomato. Both long-term and short-term risks were lower than 0.44% for all the subgroups in China, which indicated that the application of TMX was comparably acceptable. This study promotes the evaluation of TMX applied through root irrigation for use in tomato ecosystems from a dietary safety perspective.

Penthiopyrad is a novel succinate dehydrogenase inhibitor that has one chiral center and exists a metabolite, 1-methyl-3-trifluoromethyl-1H-pyrazole-4-carboxamide in its residue definition. An efficient analytical method for the simultaneous determination of penthiopyrad enantiomers and its metabolite in eight matrices were developed using modified quick, easy, cheap, effective, rugged, safe method, coupled with chiral stationary phase and ultra-high performance liquid chromatography-tandem mass spectrometry. The absolute configuration of penthiopyrad enantiomers was confirmed by polarimetry and electronic circular dichroism. Eight polysaccharide-based chiral stationary phases were evaluated in terms of the enantioseparation of penthiopyrad and separation-related factors (the mobile phase, flow rate and the column temperature) were optimized. To obtain an optimal purification, different sorbent combinations were assessed. The linearities of this method were acceptable in the range of 0.005 to 1 mg/L with R2 > 0.998, while the limits of detection and quantification were 0.0015 mg/kg and 0.01 mg/kg for two enantiomers and its metabolite. The average recoveries of R-(-)-penthiopyrad, S-(+)-penthiopyrad and the metabolite ranged from 75.4 to 109.1, 69.5 to 112.8, and 70.0 to 108.5%, respectively. The intra-day and inter-day relative standard deviations were less than 18.8%. The analytical method was accurate and convenient, which can support their further research on stereoselective degradation, residual monitoring and risk assessment.

An in-depth study of the influence mechanism of oasis land surface temperature (LST) in arid regions is essential to promote the stable development of the ecological environment in dry areas. Based on MODIS, MYD11A2 long time series data from 2003 to 2020, the Mann–Kendall nonparametric test, the Sen slope, combined with the Hurst index, were used to analyze and predict the trend of LST changes in the urban agglomeration on the northern slopes of the Tianshan Mountains. This paper selected nine influencing factors of the slope, aspect, air temperature, normalized vegetation index (NDVI), precipitation (P), nighttime light index (NTL), patch density (PD), mean patch area (AREA_MN), and aggregation index (AI) to analyze the spatial heterogeneity of LST from global and local perspectives using the geodetector (GD) model and multi-scale geo-weighted regression (MGWR) model. The results showed that the average LSTs of the urban agglomeration on the northern slopes of the Tianshan Mountains in spring, summer, autumn, and winter were 31.53 °C, 47.29 °C, 22.38 °C, and −5.20 °C in the four seasons from 2003 to 2020, respectively. Except for autumn, the LST of all seasons showed an increasing trend, bare soil and grass land had a warming effect, and agricultural land had a cooling effect. The results of factor detection showed that air temperature, P, and NDVI were the dominant factors affecting the spatial variation of LST. The interaction detection results showed that the interaction between air temperature and NDVI was the most significant, and the two-factor interaction was more effective than the single-factor effect on LST. The MGWR model results showed that the effects of PD on LST were positively correlated, and the impact of AREA_MN and AI on LST were negatively correlated, indicating that the dense landscape of patches has a cooling effect on LST. Overall, this study provides information for managers to carry out more targeted ecological stability regulations in arid zone oases and facilitates the development of regulatory measures to maintain the cold island effect and improve the environment.

The frequent application of second-generation neonicotinoids thiamethoxam (TMX) and clothianidin (CLO) has led to a high detectable rate in environment samples and poses threats to nontarget organisms and human beings, however, the information on the influences of long-term exposure at low doses was limited. In this study, the tissue distribution of TMX and CLO in mice at acceptable daily intake (ADI) level and 5 × ADI was determined and the health effects were assessed. TMX and CLO were detected in the liver, serum, lung, heart and kidney in the TMX exposure groups, which indicated that TMX degraded to CLO in mice. Residue levels of TMX in tissues increased with the increasing of doses. The concentrations of CLO in different tissues in the CLO exposure groups were in the order C

Indoxacarb is a typical chiral insecticide widely used in agricultural pest control. In the present study, zebrafish was used as a model animal to explore the enantioselective bioaccumulation behavior of indoxacarb to nontarget species in aquatic environments. Zebrafish were exposed to 0.025 and 0.1 mg/L rac-indoxacarb solution for 12 d under the semistatic method, and the bioconcentration factor (BCF) and enantiomeric fraction of zebrafish were investigated. The results showed that the (-)-R-indoxacarb preferentially accumulated in zebrafish. The BCF values at 0.025 mg/L exposure levels were 1079.8 and 83.4 L/kg for (-)-R-indoxacarb and (+)-S-indoxacarb after 12 d, respectively. The BCF values at 0.1 mg/L exposure levels were 1752.1 and 137.0 L/kg for (-)-R-indoxacarb and (+)-S-indoxacarb after 10 d, respectively. The half-life values of (-)-R-indoxacarb and (+)-S-indoxacarb were 3.47 and 2.05 d for 0.025 mg/L concentration exposure and 4.95 and 2.66 d for 0.1 mg/L concentration exposure, respectively. The enantiomeric fraction values were in the range of 0.48 to 0.55 and 0.89 to 1.00 for water and zebrafish samples, respectively. Studies on the enantioselective bioaccumulation behavior of indoxacarb will provide data for assessing the environmental fate and potential toxic effects of indoxacarb on aquatic organisms. Environ Toxicol Chem 2021;40:1007-1016. © 2020 SETAC.

The research on the enantioselective toxic effects of chiral pesticides on non-target aquatic organisms has attracted more and more attention. This study investigated the enantioselective toxic effects of mefentrifluconazole (MFZ) on acute toxicity, developmental toxicity, locomotor behaviors, and the mRNA relative expression levels of genes related to neurodevelopment and cardiac development in zebrafish embryos or larvae. The 96-h lethal concentration 50 (LC

BK type Ca2+-activated K+ channels activate in response to both the membrane voltage and intracellular Ca2+ with distinct mechanisms. Ca2+ binds to the cytosolic domain (CTD) to open the pore across the membrane, but the mechanism that couples Ca2+ binding to pore opening is not clear. Here we show that a compound, BC5, identified using in silico screening, interacts with BK channels at the interface between the CTD and the transmembrane voltage sensing domain (VSD) and enhances channel activity by specifically affecting the Ca2+ dependent mechanism. BC5 activates the channel in the absence of Ca2+ binding but Ca2+ binding inhibits BC5 effects. Thus, BC5 perturbs the pathway that couples Ca2+ binding to pore opening to allosterically affect both, which is supported by atomistic simulations and mutagensis. The results suggest that the CTD- VSD interaction makes a major contribution to the mechanism of Ca2+ dependent activation and is an important site for allosteric agonists to modulate BK channel activation.

Succinate dehydrogenase inhibitor (SDHI) fungicides has been extensively used in agricultural production, which are not easily degrade in the environment and have various toxic effects on aquatic organisms. However, the toxic effects information to non-target organisms were mostly at the racemate level, which were poorly understood at the enantiomers level. Thus, this study aimed to investigate the enantioselective bioaccumulation behavior and toxic effects of penthiopyrad in zebrafish. Significant enantioselective bioaccumulation was observed when exposed to penthiopyrad at two dose levels: S-(+)-penthiopyrad was preferentially accumulated. Moreover, S-(+)-penthiopyrad caused oxidative stress in zebrafish liver. The results of real-time RT-PCR analyses revealed that exposure to penthiopyrad also enantioselectivity interfered with the expression of mitochondrial respiratory complexes, mtDNA synthesis, lipid metabolism and apoptosis-related genes. S-(+)-penthiopyrad significantly decreased most of the expression of the above gene, which showed higher toxic effects. We inferred that the toxicity mechanism of penthiopyrad was caused by lipid metabolism disorder and mitochondrial dysfunction in zebrafish, and further leads to apoptosis even DNA damage. This study provides more accurate data to investigate the environmental impact of penthiopyrad at the enantiomer level.

The effects of different multi-walled carbon nanotubes on the enantioselective bioaccumulation and toxicity of the chiral pesticide bifenthrin to zebrafish were investigated in this work. The results showed that MWCNTs and MWCNTs-COOH did not affect the preferential bioaccumulation of 1R-cis-BF in zebrafish following exposure to cis-BF enantiomers for 28 days, but which increased cis-BF accumulation amount by 1.03-1.48 times. Further research demonstrated that the genes related to immunity, endocrine activity and neurotoxicity showed enantioselective expression in different zebrafish tissues, and sex-specific differences were observed. The levels of c-fos, th, syn2a, 17β-hsd and cc-chem were expressed as 1.09-2.84 times higher in females and males treated with 1R-cis-BF than in the 1S-cis-BF-treated groups. However, in the presence of MWCNTs or MWCNTs-COOH, c-fos, th, syn2a, 17β-hsd and cc-chem levels were expressed as 1.53-14.92 times higher in females and males treated with 1S-cis-BF than in 1R-cis-BF-treated groups, which indicated that enantioselective expression was altered. The effects of different types of MWCNTs on the enantioselective bioaccumulation and toxicity of BF in zebrafish have little difference. In summary, the presence of MWCNTs or MWCNTs-COOH increased the impact of BF on zebrafish. Therefore, the risks posed by coexisting nanomaterials and chiral pesticides in aquatic environments should be considered.

The ecological protection and sustainable development of Urumqi have become an important part of the high-quality growth of the urban agglomeration on the northern slope of Tianshan Mountain. Under the impacts of multi-source factors, the ecological landscape pattern of Urumqi has changed due to it being in a fragile eco-environment, so an ecological network is desperately needed to enhance ecological security patterns. Taking Urumqi city as the study area, the ecological risk evaluation model and the minimum cumulative resistance model were integrated to analyze the spatial and temporal features of landscape ecological risk from 2000 to 2020, and the future land use simulation model was used to predict the ecological risk pattern of Urumqi in 2030, construct a landscape ecological network, and propose ecological security protection strategies. Since 2000, land use in Urumqi has undergone drastic changes: the built-up land area has increased significantly, the landscape has diversified, and landscape fragmentation has shown a decreasing trend from the main urban area as the core to the urban fringe. The high-risk landscape ecology shows a decreasing trend from east to west, mainly in the bare land areas with sparse vegetation, whereas the risk is relatively low in woodland, arable land, and built-up areas. The change of risk in the study area is mainly influenced by the typical defective factors of oasis cities such as urban expansion, land desertification, and sparse vegetation. The landscape ecological network is mainly located in the southwest, central, and east of the study area, whereas there is no corridor distribution in the north and southeast, which is mainly caused by the special geographical location and climatic conditions. The ecological network mainly consists of 10 ecological sources and 10 ecological corridors and proposes conservation strategies for the optimization of the landscape pattern and for the construction of the ecological security pattern in Urumqi, providing a guide for the improvement of ecological security.

Cardiac arrhythmias are the most common cause of sudden cardiac death worldwide. Lengthening the ventricular action potential duration (APD) either congenitally or via pathologic or pharmacologic means, predisposes to a life-threatening ventricular arrhythmia, Torsade de Pointes. IKs, a slowly activating K+ current plays a role in action potential repolarization. In this study, we screened a chemical library in silico by docking compounds to the voltage sensing domain (VSD) of the IKs channel. Here we show that C28 specifically shifted IKs VSD activation in ventricle to more negative voltages and reversed drug-induced lengthening of APD. At the same dosage, C28 did not cause significant changes of the normal APD in either ventricle or atrium. This study provides evidence in support of a computational prediction of IKs VSD activation as a potential therapeutic approach for all forms of APD prolongation. This outcome could expand the therapeutic efficacy of a myriad of currently approved drugs that may trigger arrhythmias.Significance statementC28, identified by in silico screening, specifically facilitated voltage dependent activation of a cardiac potassium ion channel, IKs. C28 reversed drug-induced prolongation of action potentials, but minimally affected the normal action potential at the same dosage. This outcome supports a computational prediction of modulating IKs activation as a potential therapy for all forms of action potential prolongation, and could expand therapeutic efficacy of many currently approved drugs that may trigger arrhythmias.

KCNQ family K+ channels (KCNQ1-5) in the heart, nerve, epithelium and ear require phosphatidylinositol 4,5-bisphosphate (PIP2) for voltage dependent activation. While membrane lipids are known to regulate voltage sensor domain (VSD) activation and pore opening in voltage dependent gating, PIP2 was found to interact with KCNQ1 and mediate VSD-pore coupling. Here, we show that a compound CP1, identified in silico based on the structures of both KCNQ1 and PIP2, can substitute for PIP2 to mediate VSD-pore coupling. Both PIP2 and CP1 interact with residues amongst a cluster of amino acids critical for VSD-pore coupling. CP1 alters KCNQ channel function due to different interactions with KCNQ compared with PIP2. We also found that CP1 returned drug-induced action potential prolongation in ventricular myocytes to normal durations. These results reveal the structural basis of PIP2 regulation of KCNQ channels and indicate a potential approach for the development of anti-arrhythmic therapy., Yongfeng Liu, Xianjin Xu, Junyuan Gao et al. perform in silico screening targeting compounds that resemble both KCNQ1 and PIP2 structures and identify CP1 as a compound that could restore KCNQ1 currents after PIP2 depletion. Like PIP2, this compound can mediate VSD-pore coupling of the channel, albeit via a different mechanism from PIP2.

Gain-of-function mutations in the pore-forming subunit of IKs channels, KCNQ1, lead to short QT syndrome (SQTS) and lethal arrhythmias. However, how mutant IKs channels cause SQTS and the possibility of IKs-specific pharmacological treatment remain unclear. V141M KCNQ1 is a SQTS associated mutation. We studied its effect on IKs gating properties and changes in the action potentials (AP) of human ventricular myocytes. Xenopus oocytes were used to study the gating mechanisms of expressed V141M KCNQ1/KCNE1 channels. Computational models were used to simulate human APs in endocardial, mid-myocardial, and epicardial ventricular myocytes with and without β-adrenergic stimulation. V141M KCNQ1 caused a gain-of-function in IKs characterized by increased current density, faster activation, and slower deactivation leading to IKs accumulation. V141M KCNQ1 also caused a leftward shift of the conductance-voltage curve compared to wild type (WT) IKs (V1/2 = 33.6 ± 4.0 mV for WT, and 24.0 ± 1.3 mV for heterozygous V141M). A Markov model of heterozygous V141M mutant IKs was developed and incorporated into the O’Hara–Rudy model. Compared to the WT, AP simulations demonstrated marked rate-dependent shortening of AP duration (APD) for V141M, predicting a SQTS phenotype. Transmural electrical heterogeneity was enhanced in heterozygous V141M AP simulations, especially under β-adrenergic stimulation. Computational simulations identified specific IK1 blockade as a beneficial pharmacologic target for reducing the transmural APD heterogeneity associated with V141M KCNQ1 mutation. V141M KCNQ1 mutation shortens ventricular APs and enhances transmural APD heterogeneity under β-adrenergic stimulation. Computational simulations identified IK1 blockers as a potential antiarrhythmic drug of choice for SQTS.

Carbon nanotubes (CNTs) have been widely used in various fields with the rapid development of nanotechnology. Pesticides have an irreplaceable role in agricultural production, which leads to their massive utilization and their inevitably penetrate into the aquatic environment. However, limited information is available regarding the impact of CNTs on the toxicity and enrichment of chiral compounds to organisms. Using zebrafish as a model to study whether the enantioselective bioaccumulation and oxidative stress of chiral pollutants may be altered in the presence of MWCNTs. Significant enantioselective bioaccumulation was observed in zebrafish with the preferential accumulation of R-(-)-indoxacarb during the 28-day bioaccumulation. The combined exposure of MWCNTs does not affect the enantioselectivity of zebrafish bioaccumulation, but increase the bioaccumulation amount of R-(-)-indoxacarb by 65%. Moreover, the average degradation half-life of indoxacarb enantiomers was 1.30 days. The indoxacarb causes oxidative stress toxicity in zebrafish liver and exhibited enantioselectivity, while the addition of MWCNTs did not significantly change the enantioselectivity of oxidative stress toxicity of indoxacarb, but enhanced the toxicity 20% with increased MWCNTs concentrations. This study suggests that the risk of the co-presence of nanomaterials and chiral pesticides in aquatic environments should be taken into consideration.

The mass production and usage of carbon nanotubes (CNTs) have led to the inevitable release into the environment, and the effects of CNTs on the toxicity of co-existing pollutants have been well documented. However, knowledge of the effects of CNTs on the enantioselective toxicity of chiral compounds is limited. Using zebrafish as an experimental model, the enantioselective expression of the apoptosis, CYP3C and EAAT-related genes were analyzed following exposure to multi-walled carbon nanotubes (MWCNTs) (0.05 and 0.5 mg/L), rac-/R-/S-indoxacarb (0.01 mg/L), or the combination of rac-/R-/S-indoxacarb mixed with MWCNTs for 28d. Sex-specific differences were observed in both the liver and brain of zebrafish. The expression of apoptosis and CYP3C-related genes was 16.55–44.29 times higher in the livers of males treated with R-indoxacarb than in S-indoxacarb treated groups. The EAAT-related genes were expressed at 1.38–2.56 times higher levels in the brain of females treated with R-indoxacarb than in S-indoxacarb-treated groups. In the presence of MWCNTs, the expression of caspase-3, cyp3c3, cyp3c4, eaat1a, eaat1b and eaat2 in the livers of males and brains of females treated with S-indoxacarb were 1.65–15.33 times higher than in fish treated with R-indoxacarb. Based on these results, MWCNTs affected the enantioselective toxicity of indoxacarb toward zebrafish.

The enantioselective degradation of indoxacarb in cabbage and soil has been investigated in Beijing and Anhui under open conditions. Indoxacarb enantiomers in samples were extracted with acetonitrile, cleaned up by florisil SPE column, separated on high performance liquid chromatography with a cellulose-tris-(3, 5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP), and determined by a photodiode array detector. The validation of the developed method by fortification rac-indoxcarb in cabbage and soil showed good accuracy and precision. The results of field trials indicated that the dissipation of indoxacarb enantiomers followed pseudo-first-order kinetics or first-order kinetics in cabbage and soil at two locations. The half-lives of two enantiomers in cabbage ranged from 2.8 to 4.6 d which were shorter than those in soil ranging from 23 to 35 d. The changes of enantiomeric fraction values proved that enantioselective degradation of indoxacarb happened in cabbage and soil. The (−)-indoxacarb showed faster degradation in the Beijing cabbage, whereas in the Anhui cabbage, (+)-indoxacarb preferentially degraded. In soil, preferential degradation of (+)-indoxacarb was observed at two locations. Chirality 24:628–633, 2012. © 2012 Wiley Periodicals, Inc.

Clothianidin, a new neonicotinoid insecticide, was systematically evaluated. An analytical method using gas chromatography with electron capture detection was developed. Recoveries were between 92% and 102%, with relative standard deviations from 3% to 5% at three fortified levels. The decrease of clothianidin in tomato and soil samples under field conditions at Beijing, Shandong, and Anhui were determined. The dissipation rates of clothianidin fit first-order kinetics. Its half-lives ranged from 6.7 to 12.7 days in soil, and 7.0 to 11.9 days in tomato. On the suggested pre-harvest interval of 7 days, the distribution of clothianidin in tomato peel and flesh was studied. Most residues were found on the peel. Hence, removing the tomato peel before consumption is advisable. The stability of clothianidin fortified at 0.3 or 3 mg/kg in frozen green and red ripe tomatoes was also determined. The half-life mainly depended on the spiked levels of this pesticide.

Stereoselective dissipation of epoxiconazole had been studied in grape and soil during plant growing under field conditions in this paper. A sensitive and rapid chiral method was developed and validated for the determination of epoxiconazole stereoisomers in grape and soil based on liquid chromatography coupled with triple quadrupole mass spectrometry (LC-MS/MS). Phenomenex Lux Cellulose-1 column was used for enantioseparation with a mixture of acetonitrile/water (90/10, v/v) as mobile phase at flow rate of 0.3 mL min(-1). Fortified recoveries in grape and soil samples ranged from 76.0% to 91.9% and relative standard deviations were less than 11.4% with fortified levels of 0.025-1.0 mg kg(-1). The limits of detection and quantification were 0.005 mg kg(-1) and 0.025 mg kg(-1), respectively, with linear calibration curves extending up to 5.0 mg kg(-1). The field experimental results showed that dissipations of epoxiconazole stereoisomers in grape followed first-order kinetics (R(2)>0.92) and stereoselectivity occurred in 2 h after spraying. The (-)-stereoisomer with half-life of 9.3 d degraded faster than (+)-stereoisomer with that of 13.2 d, and resulted in relative enrichment of (+)-stereoisomer. However, the stereoisomeric dissipations in soil were triphasic ("increase-decrease-steady") with lower dissipation rates, and also occurred with preferential degradation of (-)-stereoisomer under field condition. The results for stereoselective dissipations can be applied for food and environmental assessments of chiral pesticides.

In the present work, the environmental fate, including residual level and dissipation rate of two formulations of ZJ0702 (a new pyrimidine salicylic herbicide which showed good inhibitory effect on the weeds in rape fields), EC and SC, were determined by high performance liquid chromatography with DAD. The herbicide was used in Hangzhou and Kunming in rape fields at the same time for 2 years. The results were that half-lives of ZJ0702 in rape ranged from 1.2-6.8 days, while in soil samples were from 15.2-47.1 days. On the sampling days, the final residues of ZJ0702 in rapeseed were below the limit of quantitation (0.02 mg/kg). The differences of dissipation rate suggest that local soil characteristics and climate, and the formulations would affect the decline of ZJ0702. The low final residue levels of ZJ0702 in rapeseed and soil indicated that this new pesticide was environmentally safe. It was recommended that MRL for ZJ0702 in rapeseed be 1 mg/kg in China.

The article “Pro-arrhythmogenic Effects of the V141M KCNQ1 Mutation in Short QT Syndrome and Its Potential Therapeutic Targets: Insights from Modeling”, written by Hsiang-Chun Lee, Yoram Rudy, Hongwu Liang, Chih-Chieh Chen, Ching-Hsing Luo, Sheng-Hsiung Sheu, Jianmin Cui was originally published Online First without open access. After publication in volume [37], issue [5], page [780–789] the author decided to opt for Open Choice and to make the article an open access publication. Therefore, the copyright of the article has been changed to © The Author(s) [2018] and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Two mammalian genes, Kcnt1 and Kcnt2, encode pore-forming subunits of Na+-dependent K+ (KNa) channels. Progress in understanding KNa channels has been hampered by the absence of specific tools and methods for rigorous KNa identification in native cells. Here, we report the genetic disruption of both Kcnt1 and Kcnt2, confirm the loss of Slo2.2 and Slo2.1 protein, respectively, in KO animals, and define tissues enriched in Slo2 expression. Noting the prevalence of Slo2.2 in dorsal root ganglion, we find that KO of Slo2.2, but not Slo2.1, results in enhanced itch and pain responses. In dissociated small diameter DRG neurons, KO of Slo2.2, but not Slo2.1, abolishes KNa current. Utilizing isolectin B4+ neurons, the absence of KNa current results in an increase in action potential (AP) firing and a decrease in AP threshold. Activation of KNa acts as a brake to initiation of the first depolarization-elicited AP with no discernible effect on afterhyperpolarizations. DOI: http://dx.doi.org/10.7554/eLife.10013.001, eLife digest The billions of neurons in the brain send information along their lengths in the form of electrical signals called action potentials. These signals are produced by charged ions, such as sodium and potassium ions, moving into and out of the neuron. To ‘fire’ an action potential, sodium ions rapidly enter the neuron. This produces an electrical spike. Potassium ions then exit the neuron, which causes the electrical activity to subside and allows the neuron to return to a resting state. The sodium and potassium ions move in and out of the neuron through structures called ion channels. The sodium-activated potassium channels are one type of ion channel; whether these ion channels let potassium ions out of a cell depends on the concentration of sodium ions inside the cell. Slo2.1 and Slo2.2 are two such potassium channels that are present in many different cells, including neurons. Nevertheless, and in spite of how common they are, the exact roles of these channels remain unclear. Martinez-Espinosa et al. created mice that lack the genes encoding one or both of the Slo2.1 and Slo2.2 ion channels, and compared them with normal mice. Mice that lacked Slo2.2 but not Slo2.1 initially scratched more intensely than normal mice when made to feel an itch, though this increased scratching only occurred briefly. To some extent, the mice that lacked both Slo2 channels also had increased pain sensations. Martinez-Espinosa et al. observed that in sensory neurons lacking the Slo2.2 sodium-dependent potassium channels, the neurons fired more action potentials. The increase in firing is thought to underlie the enhanced itching and pain sensations. Taken together, the results suggest that the activity of sodium-activated potassium ion channels makes it less likely for a neuron to fire an action potential. Future work will need to address whether the activity of sodium-activated potassium channels is linked to specific kinds of sodium channels, and why the absence of the sodium-activated potassium current only enhances the immediate response to itch stimuli. The availability of these mice that lack Slo2 subunits provides an important new tool for evaluating the role of sodium-activated channels in other neuronal systems. DOI: http://dx.doi.org/10.7554/eLife.10013.002