Differential Effect of Calcium-Activated Potassium and Chloride Channels on Rat Basilar Artery Vasomotion

Spontaneous, rhythmical contractions, or vasomotion, can be recorded from cerebral vessels under both normal physiological and pathophysiological conditions. We investigated the cellular mechanisms underlying vasomotion in the cerebral basilar artery （BA） of Wistar rats. Pressure myograph video microscopy was used to study the changes in cerebral artery vessel diameter. The main results of this study were as follows： （1） The diameters of BA and middle cerebral artery （MCA） were 314.5±15.7 μm （n=15） and 233.3±10.1 μm （n=12） at 10 mmHg working pressure （P〈0.05）, respectively. Pressure-induced vasomotion occurred in BA （22/28, 78.6%）, but not in MCA （4/31, 12.9%） from 0 to 70 mmHg working pressure. As is typical for vasomotion, the contractile phase of the response was more rapid than the relaxation phase; （2） The frequency of vasomotion response and the diameter were gradually increased in BA from 0 to 70 mmHg working pressure. The amplitude of the rhythmic con- tractions was relatively constant once stable conditions were achieved. The frequency of contractions was variable and the highest value was 16.7±4.7 （n=13） per 10 min at 60 mmHg working pressure; （3） The pressure-induced vasomotion of the isolated BA was attenuated by nifedipine, NFA, 181]-GA, TEA or in Ca2＋-free medium. Nifedipine, NFA, 18^-GA or Ca2＋-free medium not only dampened vasomotion, but also kept BA in relaxation state. In contrasts, TEA kept BA in contraction state. These results sug- gest that the pressure-induced vasomotion of the isolated BA results from an interaction between Ca2＋-activated C1- channels （CaCCs） currents and Kca currents. We hypothesize that vasomotion of BA depends on the depolarizing of the vascular smooth muscle cells （VSMCs） to activate CaCCs. Depolarization in turn activates voltage-dependent Ca2＋ channels, synchronizing contractions of adjacent cells through influx of extracellular calcium and the flow of calcium through gap junctions. Subsequent calcium-induced calcium release from ryanodine-sensitive stores activates Kca channels and hyperpo- larizes VSMCs, which provides a negative feedback loop for regenerating the contractile cycle.

Endothelium-derived Relaxing Factor Activates Calcium-activated Potassium Channels of Resistance Vessel Smooth Muscle Cells

Direct observation was made by using the patch-clamp technique with a specially designed microperfusion system to investigate the effect of acetylcholine (Ach 10^(-6) mol/L) elicited endothelium-derived relaxing factor (EDRF) on the calcium-activated potassium channel (IK(Ca))in the smooth muscle cells of mesenteric resistance vessels in Wistar rats. Activation of IK(Ca) was firstly observed by inducing the elicited EDRF or sodium nitroprusside (SNP 10^(-8) mol/L) under various clamping voltages in cell-attached configuration. While the pipette solution contained KCl 126 mmol/L and the bath solution contained KCl 5.9 mmol/L, two types of conductances of calcium-activated potassium current being 76.4±2.3 pS(mean±S.E. n = 7) and 160.3±7.5 pS (mean±S.E. n= 7) were recorded during the EDRF activation, one type of conductance being 100.5±2.8 pS (mean±S.E. n = 6) was activated by nitric oxide (NO) which is an effective component from SNP. Differences in kinetic characteristics of these channels between EDRF and NO activation were found, particularly the probability of the channel being open in EDRF activation was obviously greater than that in NO stimulation. It has been shown that the potassium channel mechanisms involved in the EDRF and NO actions might be different.

Effects of unsaturated fatty acids on calcium-activated potassium current in gastric myocytes of guinea pigs

AIM: To investigate the effects of exogenous unsaturated fatty acids on calcium-activated potassium current [IK(Ca)] in gastric antral circular myocytes of guinea pigs. METHODS: Gastric myocytes were isolated by collagenase from the antral circular layer of guinea pig stomach. The whole-cell patch clamp technique was used to record /K(Ca) in the isolated single smooth muscle cells with or without different concentrations of arachidonic acid (AA), linoleic acid (LA), and oleic acid (OA). RESULTS: AA at concentrations of 2,5 and 10 μmol/L markedly increased IK(Ca) in a dose-dependent manner. LA at concentrations of 5, 10 and 20 μmol/L also enhanced /K(Ca) in a dose-dependent manner. The increasing potency of AA, LA, and oleic acid (OA) on /K(Ca)at the same concentration (10μmol/L) was in the order of AA>LA>OA. AA (10 μmol/L)-induced increase of Ik(ca) was not blocked by H-7 (10 μmol/L), an inhibitor of protein kinase C (PKC), or indomethacin (10 μmol/L), an inhibitor of the cyclooxygenase pathway, and 17-octadecynoic acid (10 μmol/L), an inhibitor of the cytochrome P450 pathway, but weakened by nordihydroguaiaretic acid (10μmol/L), an inhibitor of the lipoxygenase pathway. CONCLUSION: Unsaturated fatty acids markedly increase Ik(Ca), and the enhancing potencies are related to the number of double bonds in the fatty acid chain. The lipoxygenase pathway of unsaturated fatty acid metabolism is involved in the unsaturated fatty acid-induced increase of IK(Ca) in gastric antral circular myocytes of guinea pigs.

Astrocytic Kir4.1 potassium channels as a novel therapeutic target for epilepsy and mood disorders

Astrocytic Kir4.1 channels and spatial potassium buffering：Astrocytes play a crucial role in maintaining the structural and functional integrity of the brain,which includes formation of the blood-brain barrier,maintenance of water and ion homeostasis,metabolism of neurotransmitters and secretion of various neuroactive molecules.

Effects of ATP-sensitive Potassium Channels on the Expression of P21, P27 and Leptin

This study investigated the effects of ATP-sensitive potassium channels on the expression of P21, P27 and leptin. The expression of receptor of ATP-sensitive potassium channels （sulphonylurea receptor, SUR） mRNA in the preadipocytes and leptin mRNA was detected by PCR after rat preadipocytes were treated with the opener （diazoxide） or inhibitor （glibenclamide） of ATP-sensitive potassium channels during the process of inducing differentiation. The expression of P21 and P27 in preadipocytes treated with diazoxide or glibenclamide was assayed by Western blot. The results showed that the expression of SUR2, not SUR1 was detected in adipose tissue, preadipocytes and adipocytes. Alter treatment of preadipocytes with diazoxide, the expression levels of P21 and P27 were obviously higher than glibenclamide-treat ed group those in control group, but the were lower than those in control expression levels of P21 and P27 in group. During the process of inducing differentiation, the expression of leptin mRNA in preadipocytes treated with diazoxide was increased greatly, but the expression of leptin mRNA in glibenclamide-treated group decreased obviously. It was concluded that ATP-sensitive potassium channels might be involved in the proliferation and differentiation of rat preadipocytes by changing the expression of P21, P27 and leptin.

The genetic study of ischemia induced arrhythmia and potassium channels

Objectives Ischemia induced arrhythmia(ventricular tachycardia/ventricular fibrillation) is one of the major causes of death.Potassium channels change are likely to be responsible for the ischemia-related arrhythmias.Cardiac potassium current is the major outward current involved in cardiac repolarization.The properties of potassium channels have been intensively studied.Here,we investigated the association between ischemia induced arrhythmia and potassium channels genetic variations.Methods 23 patients with ventricular tachycardia/ventricular fibrillation induced by ischemia were selected as objects.5ML peripheral blood were taken from each person,from which DNA was extracted us- ing a standard enzymatic phenol-chloroform method.Candidate genes(HERG、KCNJ2、KCNQ1、Mink、Mirp1、Kir2.1、KV4.3、Kir3.1、KV1.5、Kir6.1、Kir6.2、Kir2.1) Were screened for potassium channels gene mutations with direct sequencing methods.Results Here 4 potassium channels gene mutations have been discovered.In the gene coding for the ATP-sensitive K^+ channels subunit Kir6.2,there is a change from valine to isoleucine at the position of 326(V326I).At the position 448,arginine substitutes proline(P448R) in the KC-NQ1 gene.In the gene KCNJ2 two mutations have been found(P156L,Q193H).Conclusions This study implicated that there is a high relationship between ischemia induced arrhythmia and the mutation of potassium channels.In order to identify the precisely relationship there is need functional analysis.

Role of Voltage-gated Potassium Channels in Pathogenesis of Chronic Pulmonary Heart Disease

The influence of hypoxia on the activity of voltage-gated potassium channel in pulmonary artery smooth muscle cells （PASMCs） of rats and its roles in the pathogenesis of chronic pulmonary heart disease were investigated. Eighty male Sprague-Dawley rats were randomly allocated into control group （n=10）, acute hypoxic group （n=10）, and chronic hypoxic groups （n=60）. The chronic hypoxic groups were randomly divided into 6 subgroups （n=10 each） according to the chronic hypoxic periods. The rats in the control group were kept in room air and those in acute hypoxic group in hypoxia envi- ronmental chamber for 8 h. The rats in chronic hypoxic subgroups were kept in hypoxia environmental chamber for 8 h per day for 5, 10, 15, 20, 25, and 30 days, respectively. The mean pulmonary arterial pressure （mPAP）, right ventricular hypertrophy index （RVHI）, and the current of voltage-gated potas- sium channel （IK） in PASMCs were measured. Results showed that both acute and chronic hypoxia could decrease the IK in PASMCs of rats and the I-V relationship downward shifted to the right. And the peak Ir density at ＋60mV decreased with prolongation of hypoxia exposure. No significant difference was noted in the density oflK （at ＋60 mV） and I-V relationship between control group and chronic hy- poxic subgroup exposed to hypoxia for 5 days （P〉0.05）, but there was a significant difference between control group and chronic hypoxic subgroup exposed to hypoxia for 10 days （P〈0.05）. Significant dif- ferences were noted in the IK density （at ＋60 mV） and I-V relationships between control group and chronic hypoxic subgroups exposed to hypoxia for 20 days and 30 days （P〈0.01）. Compared with con- trol rats, the mPAP and RVHI were significantly increased after chronic exposure to hypoxia for 10 days （P〈0.05）, which were further increased with prolongation of hypoxia exposure, and there were signifi- cant differences between control group and chronic hypoxic subgroups exposed to hypoxia for 20 days and 30 days （P〈0.01）. Both the mPAP and the RVHI were negatively correlated with the density OflK （r---0.89769 and -0.94476, respectively, both P〈0.01）. It is concluded that exposure to hypoxia may cause decreased activity of voltage-gated potassium channel, leading to hypoxia pulmonary vasocon- striction （HPV）. Sustained HPV may result in chronic pulmonary hypertension, even chronic pulmonary heart disease, contributing to the pathogenesis of chronic pulmonary heart disease.

Extract from Buthus martensii Karsch is associated with potassium channels on glioma cells

Catilan extracted from Leiurus quinquestriatus is a specific ion channel blocker.It can specifically bind chloride channels of glioma cells and kill these tumor cells.The questions remain as to whether antigliomatin,the extract from scorpion venom of Buthus martensii Karsch in China,can inhibit glioma growth,and whether this inhibition is correlated with ion channels of tumor cells.The present study treated rat C6 glioma cells with 0.8,1.2,and 1.6 μg/mL antigliomatin for 20 hours.Whole-cell patch clamp technique showed that antigliomatin delayed rectifier potassium channels of C6 glioma cells.Antigliomatin inhibited tumor growth,which could potentially involve potassium channels of tumor cells.

ATP-sensitive potassium channels:novel potential roles in Parkinson's disease

The ATP-sensitive potassium（KATP）channels which extensively distribute in diverse tissues（e.g.vascular smooth muscle,cardiac cells,and pancreas）are well-established for characteristics like vasodilatation,myocardial protection against ischemia,and insulin secretion.The aim of this review is to get insight into the novel roles of KATPchannels in Parkinson＇s disease（PD）,with consideration of the specificities KATPchannels in the central nervous system（CNS）, such as the control of neuronal excitability,action potential,mitochondrial function and neurotransmitter release.

Migration-associated secretion of melanoma inhibitory activity at the cell rear is supported by KCa3.1 potassium channels

Malignant melanoma, characterized by invasive local growth and early formation of metastases, is the most aggressive type of skin cancer. Melanoma inhibitory activity （MIA）, secreted by malignant melanoma cells, interacts with the cell adhesion receptors, integrins a4131 and 05131, facilitating cell detachment and promoting formation of me- tastases. In the present study, we demonstrate that MIA secretion is confined to the rear end of migrating cells, while in non-migrating cells MIA accumulates in the actin cortex. MIA protein takes a conventional secretory pathway including coat protein complex I （COPI）- and coat protein complex II （COPII）-dependent protein transport to the cell periphery, where its final release depends on intracellular Ca2＋ ions. Interestingly, the Ca2＋-activated K＋-channel, subfamily N, member 4 （KCa3.1）, known to be active at the rear end of migrating cells, was found to support MIA secretion. Secretion was diminished by the specific KCa3.1 channel inhibitor TRAM-34 and by expression of dominant- negative mutants of the channel. In summary, we have elucidated the migration-associated transport of MIA protein to the cell rear and also disclosed a new mechanism by which KCa3.1 potassium channels promote cell migration.

The Effect of Levobunolol Hydrochloride on the Calcium andPotassium Channels in Isolated Ventricular Myocytes of Guinea Pig

The effects of levobunolol hydrochlorid (Bun) on the type L calciumchannel currents (Ica) and delayed rectifier potassium channel currents (Ik) in isolated ventricular myocytes of guinea pig were studied by using patch clamp wholecell recording techniques. The results were showed that: 1) Bun caused a dosedependent decrease in Ica and a dose-dependent increase in Ik of the ventricular myocytes.The threshold concentrations of Bun for Ica and Ik were 10-8 mol/L and10-7 mol/L respectively. The maximum effective concentration of Bun for both Ica and Ik was 3 × 10-5 mol/L, and half-maximal concentration was 3 × 10-6 mol/L;2 ) Ik was blocked by 2× 10-6mol/L tetraethylammonium (TEA). A concentration of 3 × 10-6 mol/L Bun showed a decreasing effect on the Ica as revealed by the current-voltage relationship curve, i. e., Bun caused an elevation of the curve; 3)When Ica was blocked by 2 × 10-6 mol/L Isoptin (Verapamil), at a concentrationof 3 × 106- mol/L Bun showed an increasing effect on Ik and the effect could be blocked by TEA. The above-mentioned results indicated that Bun had an inhibito-ry effect on Ica and a fascilitatory effect on Ik The results suggested that themolecular mechanisms of antihypertensive, heart rate slowing and β-receptorblocking effects of Bun might be due to decrease of Ica and increase of Ik.

Effect of genistein on voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells

AIM： To investigate the action of genistein （GST）, a broad spectrum tyrosine kinase inhibitor, on voltagegated potassium channels in guinea pig proximal colon smooth muscle cells. METHODS： Smooth muscle cells in guinea pig proximal colon were enzymatically isolated. Nystatin-perforated whole cell patch clamp technique was used to record potassium currents including fast transient outward current （Ikto） and delayed rectifier current （Ikdr）, tWO of which were isolated pharmacologically with 10 mmol/L tetraethylammonium or 5 mmol/L 4-aminopyridine. Contamination of calcium-dependent potassium currents was minimized with no caldum and 0.2 mmol/L CdCl2 in an external solution. RESULTS： GST （10-100 μmol/L） reversibly and dosedependently reduced the peak amplitude of Ikto with an IC50 value of 22.0±6.9 μmol/L. To a lesser extent, Ikdr, was also inhibited in both peak current and sustained current. GST could not totally block the outward potassium current as a fraction of the outWard potassium current, which was insensitive to GST. GST had no effect on the steady-state activation （n =6） and inactivation kinetics （n =6） of Ikto. Sodium orthovanadate （1 retool/L）, a potent inhibitor of tyrosine phosphatase, significantly inhibited GST-induced inhibition （P〈 0.05）. CONCLUSION： GST can dose-dependently and reversibly block voltage-gated potassium channels in guinea pig proximal colon smooth muscle cells.

Regulation of adenosine triphosphate-sensitive potassium channels suppresses the toxic effects of amyloid-beta peptide(25-35)

In this study, we treated PC12 cells with 0-20 μM amyloid-β peptide （25-35） for 24 hours to induce cytotoxicity, and found that 5-20 μM amyloid-β peptide （25-35） decreased PC12 cell viability, but adenosine triphosphate-sensitive potassium channel activator diazoxide suppressed the decrease in PC12 cell viability induced by amyloid-β peptide （25-35）. Diazoxide protected PC12 cells against amyloid-β peptide （25-35）-induced increases in mitochondrial membrane potential and intracellular reactive oxygen species levels. These protective effects were reversed by the selective mitochondrial adenosine triphosphate-sensitive potassium channel blocker 5-hydroxydecanoate. An inducible nitric oxide synthase inhibitor, Nw-nitro-L-arginine, also protected PC12 cells from amyloid-β peptide （25-35）-induced increases in both mitochondrial membrane potential and intracellular reactive oxygen species levels. However, the H202-degrading enzyme catalase could not reverse the amyloid-β peptide （25-35）-induced increase in intracellular reactive oxygen species. A 24-hour exposure to amyloid-13 peptide （25-35） did not result in apoptosis or necrosis, suggesting that the increases in both mitochondrial membrane potential and reactive oxygen species levels preceded cell death. The data suggest that amyloid-β peptide （25-35） cytotoxicity is associated with adenosine triphosphate-sensitive potassium channels and nitric oxide. Regulation of adenosine triphosphate-sensitive potassium channels suppresses PC12 cell cytotoxicity induced by amyloid-β peptide （25-35）.

The role of potassium channels in the nitric oxide-induced relaxation of human airway smooth muscle of passively sensitization by serum from allergic asthmatic patients

Objective： To investigate the role of large Ca^2＋-activated, delayed-rectifier and ATP-sensitive potassium channel in regulating the relaxation induced by nitric oxide （NO） in normal and passively sensitized human airway smooth muscle （HASM） with serum from asthmatic patients. Methods： The effects of NO or/and potassium channel blockers on the tensions of normal and passively sensitized HASM were measured by using nitric oxide donor and potassium blockers, with the isometric tension recording technique. Results： Showed that（1）In the control group and passively sensitized group, Kv blocker（4-AP） cause concentration-dependent augmentation in the contraction induced by histamine （ 1 ×10^-4 mol/L ）, （P 〈 0.05）, but Glib （ 1 × 10^-2 mol/L ） and TEA （1×10^-4 mol/L） have no significant effects on the contraction induced by histamine （1×10^-4 mol/L）. The maximum tension induced by histamine in passively sensitized group is higher than that in the control group （P 〈 0.05）. （2） NO-donor Sodium Nitroprusside （SNP） bring about significant relaxation in normal and passively sensitized HASM rings （P 〈 0.05）. Relaxations of passively sensitized airway rings [ （29.4 ± 3.3）% ] were significant less than those of normal HASM rings [ （44.1 ± 10.2）% ], （P 〈 0.05）.（3） Glib（1×10^-2 mol/L）have no significant effect on the relaxations induced by SNP（1×10^-4 mol/L）. 4-AP（1×10^-2 mol/L） inhibited relaxation induced by SNP （1×10^-4 mol/L）, （P 〈 0.01）. TEA （1×10^-3 tool/L） inhibited relaxation induced by SNP （1×10^-4 mol/L） （P 〈 0.05）, and the inhibiting effect in passively sensitized HASM rings were significant less than in normal HASM, （P 〈 0.05）. Conclusion： It was concluded that SNP（NO-donor） relaxed the contraction of HASM partly via BKca channel opening. In passively sensitized HASM in vitro, the relaxation of SNP decreased compared with control group, which might be associated with the down-regulating activity of BKca in passively sensitized HASM.

Changes of Ca^2+ activated potassium channels and cellular proliferation in autogenous vein grafts

Objective: To investigate changes of Ca2+ activated potassium channels (KCa) in autogenous vein grafts. Methods: Contraction of venous ring was measured by means of perfusion in vitro. The intimal rabbits proliferation of vascular and proliferation of cultured smooth muscle cells(vascular smooth muscle cells, VSMCs)were observed by the means of computerised image analysis and MTT method respectively. Furthermore, whole cell mode of patch clamp was used to record KCa of VSMCs isolated from autogenous vein grafts. Results: One week after transplantation there were no significant differences of contraction and intimal relative thickness between autogenous vein grafts and control. Contraction and intimal relative thickness of autogenous vein graft were significantly increased 2 weeks after transplantation (P<0.05, n=8 vs control), and they was more enhanced 4 weeks after vein transplantation (P<0.01, n=8 vs control).TEA(blocker of Ca2+ activated potassium channels)increased MTT A490 nm value of VSMCs from femoral vein in a dose dependent manner(P<0.05, n=8). KCa current density was significantly attenuated in VSMCs from autogenous vein grafts (1-4) week after transplantation(P<0.05, n=5).Conclusion: KCa is inhibited in autogenous vein graft, which account for vasospasm and intimal proliferation.

Effect of G_(αq/11) Protein and ATP-sensitive Potassium Channels on Ischemic Preconditioning in Rat Hearts

Objectives To investigate the effect of Gαq/11 signaling pathway and ATP-sensitive potassium channel ( KATP channel ) on ischemic preconditioning (IPC) protection in rat hearts. Methods Two series of experiments were performed in Wistar rat hearts. In the first series of experiment, ischemic preconditioning was induced by left anterior descending occlusion (three, 5 min episodes separated by 5 min of reperfusion), ischemia-reperfusion injury was induced by 30 min coronary artery occlusion followed by 90 min reperfusion. Hemodynamics, infarct size and scores of ventricular arrhythmias were measured. The expression of Gαq/11 protein in the heart was measured by Western blot analysis in the second series. Results Ischemic preconditioning rats showed decreased infarct size and scores of ventricular arrhythmia vs non-IP control rats. The effect of IPC was significantly attenuated by glibenclamide (1 mg/kg, ip), a nonselective KATP channel inhibitor. IPC caused a significant increase in the expression of Gαq/11 protein. Conclusions Activations of Gαq/11 signal pathway and KATP channel played significant roles in the classical cardioprotection of ischemic precon-ditioning rat heart and might be an important mechanism of signal transduction pathway during the ischemic preconditioning.

POTASSIUM CHANNELS ON CARDIOMYOCYTES OF SELENIUM IODINE DEFICIENCY RATS AND IODINE DEFICIENCY RATS

Uging diet control method to feed the weaning male Wistar rats with selenium and iodine deficiency Keshan endemic area food for 8 weeks to set up animal model. Singal channel recortling in cell attached model was used to measure cardiac cell membrane potassium channel conductances. which coincide with the cardiac cell membrane potassium channel conductances in normal Wistar rats.The potassium channel conductance on selenlum and lodine cleficiency rat cardiac cell membrane is showing current-voltage increasing lineally in the range of clamping volatge 0±30 mV with channel conductance of 43.4 pS. The channel current does not increase depending on the clamping voltage that is showing the rectifying characteristic and the channel current amplitude can be augmented by added KIOa 5 mmol/L in bath solution. A kind of inward rectiyfing potassium channel activity was recorded, but this channel activity disappeared affer lasting 6～ 10 minutes only. Then an inward rectifying potassium channel with the conductance of 11. 2 PS was activated by KIOa 5 mmol/L, introduced to bath solution. Both conductances are less than that of normal Wistar rats.

Potassium and calcium channels in different nerve cells act as therapeutic targets in neurological disorders

The central nervous system, information integration center of the body, is mainly composed of neurons and glial cells. The neuron is one of the most basic and important structural and functional units of the central nervous system, with sensory stimulation and excitation conduction functions. Astrocytes and microglia belong to the glial cell family, which is the main source of cytokines and represents the main defense system of the central nervous system. Nerve cells undergo neurotransmission or gliotransmission, which regulates neuronal activity via the ion channels, receptors, or transporters expressed on nerve cell membranes. Ion channels, composed of large transmembrane proteins, play crucial roles in maintaining nerve cell homeostasis. These channels are also important for control of the membrane potential and in the secretion of neurotransmitters. A variety of cellular functions and life activities, including functional regulation of the central nervous system, the generation and conduction of nerve excitation, the occurrence of receptor potential, heart pulsation, smooth muscle peristalsis, skeletal muscle contraction, and hormone secretion, are closely related to ion channels associated with passive transmembrane transport. Two types of ion channels in the central nervous system, potassium channels and calcium channels, are closely related to various neurological disorders, including Alzheimer's disease, Parkinson's disease, and epilepsy. Accordingly, various drugs that can affect these ion channels have been explored deeply to provide new directions for the treatment of these neurological disorders. In this review, we focus on the functions of potassium and calcium ion channels in different nerve cells and their involvement in neurological disorders such as Parkinson's disease, Alzheimer's disease, depression, epilepsy, autism, and rare disorders. We also describe several clinical drugs that target potassium or calcium channels in nerve cells and could be used to treat these disorders. We concluded that there are few clinical drugs that can improve the pathology these diseases by acting on potassium or calcium ions. Although a few novel ion-channelspecific modulators have been discovered, meaningful therapies have largely not yet been realized. The lack of target-specific drugs, their requirement to cross the blood–brain barrier, and their exact underlying mechanisms all need further attention. This review aims to explain the urgent problems that need research progress and provide comprehensive information aiming to arouse the research community's interest in the development of ion channel-targeting drugs and the identification of new therapeutic targets for that can increase the cure rate of nervous system diseases and reduce the occurrence of adverse reactions in other systems.

Dual effects of tetrandrine on calcium-activated potassium channels in pulmonary artery smooth muscle cells

目的：研究粉防己碱（Ｔｅｔ）对大鼠肺动脉平滑肌细胞钙激活钾（ＫＣａ）通道的影响．方法：内面朝外膜片箝单通道记录法．结果：Ｔｅｔ７５和１５μｍｏｌ·Ｌ－１使ＫＣａ的开放概率由０２５１±００１２增加到０３４０±００１３和０４１５±００１１（Ｐ＜００１）．关闭时间由（６１±１５）ｍｓ缩短到（３３±１０）和（２８±１１）ｍｓ（Ｐ＜００１）．Ｔｅｔ３０μｍｏｌ·Ｌ－１使开放概率和开放时间分别降低到（０１１４±０００８）和（１４７±００９）ｍｓ（Ｐ＜０．０１）．结论：Ｔｅｔ对大鼠肺动脉平滑肌细胞ＫＣａ通道有双重作用．

Effect of nitric oxide-induced tyrosine phosphorylation of calcium-activated potassium channel α subunit on vascular hyporesponsiveness in rats

Objective: To study the effect of nitric oxide-induced tyrosine phosphorylation of large-conductance calcium-activated potassium (BK Ca) channel α subunit on vascular hyporesponsiveness in rats. Methods: A total of 46 Wistar rats of either sex, weighing 250 g±20 g, were used in this study. Models of vascular hyporesponsiveness induced by hemorrhagic shock (30 mm Hg for 2 hours) in vivo and by L-arginine in vitro were established respectively. The vascular responsiveness of isolated superior mesenteric arteries to norepinephrine was observed. Tyrosine phosphorylation of BK Ca α subunit was evaluated with methods of immunoprecipitation and Western blotting. Results: In the smooth muscle cells of the superior mesenteric arteries, the expression of BK Ca α subunit tyrosine phosphorylation increased following hemorrhagic shock, and L-arginine could induce BK Ca channel α subunit tyrosine phosphorylation in a time- and dose-dependent manner. L-NAME (Nω-nitro-L-arginine-methyl-ester), a nitric oxide synthetase inhibitor, could partly restore the decreased vasoresponsiveness of the superior mesenteric arteries after hemorrhagic shock in rats. Down-regulating the protein tyrosine phosphorylation with genistein, a widely-used special protein tyrosine kinase inhibitor, could partly improve the decreased vasoresponsiveness of the superior mesenteric arteries induced by L-arginine in vitro, while up-regulating the protein tyrosine phosphorylation with Na3VO4, a protein tyrosine phosphatase inhibitor, could further decrease the nitric oxide-induced vascular hyporesponsiveness, which could be partly ameliorated by 0.1 mmol/L tetrabutylammonium chloride (TEA), a selective BK Ca inhibitor at this concentration. Conclusions: Nitric oxide can induce the tyrosine phosphorylation of BK Ca α subunit, which influences the vascular hyporesponsiveness in hemorrhagic shock rats or induced by L-arginine in vitro.