Perforated patch-clamp recording in cardiac myocytes using cation-selective ionophore gramicidin

Perforated Patch Clamp Recordings in ex vivo Brain Slices from Adult Mice

Intracellular signaling pathways directly and indirectly regulate neuronal activity. In cellular electrophysiological measurements with sharp electrodes or whole-cell patch clamp recordings, there is a great risk that these signaling pathways are disturbed, significantly altering the electrophysiological properties of the measured neurons. Perforated-patch clamp recordings circumvent this issue, allowing long-term electrophysiological recordings with minimized impairment of the intracellular milieu. Based on previous studies, we describe a superstition-free protocol that can be used to routinely perform perforated patch clamp recordings for current and voltage measurements.

Acetylcholine Reduces L-Type Calcium Current without Major Changes in Repolarization of Canine and Human Purkinje and Ventricular Tissue

Vagal nerve stimulation (VNS) holds a strong basis as a potentially effective treatment modality for chronic heart failure, which explains why a multicenter VNS study in heart failure with reduced ejection fraction is ongoing. However, more detailed information is required on the effect of acetylcholine (ACh) on repolarization in Purkinje and ventricular cardiac preparations to identify the advantages, risks, and underlying cellular mechanisms of VNS. Here, we studied the effect of ACh on the action potential (AP) of canine Purkinje fibers (PFs) and several human ventricular preparations. In addition, we characterized the effects of ACh on the L-type Ca²⁺ current (I_CaL) and AP of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and performed computer simulations to explain the observed effects. Using microelectrode recordings, we found a small but significant AP prolongation in canine PFs. In the human myocardium, ACh slightly prolonged the AP in the midmyocardium but resulted in minor AP shortening in subepicardial tissue. Perforated patch-clamp experiments on hiPSC-CMs demonstrated that 5 µM ACh caused an ≈15% decrease in I_CaL density without changes in gating properties. Using dynamic clamp, we found that under blocked K⁺ currents, 5 µM ACh resulted in an ≈23% decrease in AP duration at 90% of repolarization in hiPSC-CMs. Computer simulations using the O'Hara-Rudy human ventricular cell model revealed that the overall effect of ACh on AP duration is a tight interplay between the ACh-induced reduction in I_CaL and ACh-induced changes in K⁺ currents. In conclusion, ACh results in minor changes in AP repolarization and duration of canine PFs and human ventricular myocardium due to the concomitant inhibition of inward I_CaL and outward K⁺ currents, which limits changes in net repolarizing current and thus prevents major changes in AP repolarization.

Analysis of neuronal Ca2+ handling properties by combining perforated patch clamp recordings and the added buffer approach

Ca2+ functions as an important intracellular signal for a wide range of cellular processes. These processes are selectively activated by controlled spatiotemporal dynamics of the free cytosolic Ca2+. Intracellular Ca2+ dynamics are regulated by numerous cellular parameters. Here, we established a new way to determine neuronal Ca2+ handling properties by combining the 'added buffer' approach [1] with perforated patch-clamp recordings [2]. Since the added buffer approach typically employs the standard whole-cell configuration for concentration-controlled Ca2+ indicator loading, it only allows for the reliable estimation of the immobile fraction of intracellular Ca2+ buffers. Furthermore, crucial components of intracellular signaling pathways are being washed out during prolonged whole-cell recordings, leading to cellular deterioration. By combining the added buffer approach with perforated patch-clamp recordings, these issues are circumvented, allowing the precise quantification of the cellular Ca2+ handling properties, including immobile as well as mobile Ca2+ buffers.

Astrocytic modulation of excitatory synaptic signaling in a mouse model of Rett syndrome

Studies linking mutations in Methyl CpG Binding Protein 2 (MeCP2) to physiological defects in the neurological disease, Rett syndrome, have focused largely upon neuronal dysfunction despite MeCP2 ubiquitous expression. Here we explore roles for astrocytes in neuronal network function using cortical slice recordings. We find that astrocyte stimulation in wild-type mice increases excitatory synaptic activity that is absent in male mice lacking MeCP2 globally. To determine the cellular basis of the defect, we exploit a female mouse model for Rett syndrome that expresses wild-type MeCP2-GFP in a mosaic distribution throughout the brain, allowing us to test all combinations of wild-type and mutant cells. We find that the defect is dependent upon MeCP2 expression status in the astrocytes and not in the neurons. Our findings highlight a new role for astrocytes in regulation of excitatory synaptic signaling and in the neurological defects associated with Rett syndrome.

Quantitative Profiling of the Effects of Vanoxerine on Human Cardiac Ion Channels and its Application to Cardiac Risk

Vanoxerine has been in clinical trials for Parkinsonism, depression and cocaine addiction but lacked efficacy. Although a potent blocker of hERG, it produced no serious adverse events. We attributed the unexpected result to offsetting Multiple Ion Channel Effects (MICE). Vanoxerine’s effects were strongly frequency-dependent and we repositioned it for treatment of atrial fibrillation and flutter. Vanoxerine terminated AF/AFL in an animal model and a dose-ranging clinical trial. Reversion to normal rhythm was associated with QT prolongation yet absent proarrhythmia markers for Torsade de Pointes (TdP). To understand the QT/TdP discordance, we used quantitative profiling and compared vanoxerine with dofetilide, a selective hERG-blocking torsadogen used for intractable AF, verapamil, a non-torsadogenic MICE comparator and bepridil, a torsadogenic MICE comparator. At clinically relevant concentrations, verapamil blocked hCav1.2 and hERG, as did vanoxerine and bepridil both of which also blocked hNav1.5. In acute experiments and simulations, dofetilide produced early after depolarizations (EADs) and arrhythmias, whereas verapamil, vanoxerine and bepridil produced no proarrhythmia markers. Of the MICE drugs only bepridil inhibited hERG trafficking following overnight exposure. The results are consistent with the emphasis on MICE of the CiPA assay. Additionally we propose that trafficking inhibition of hERG be added to CiPA.

Trafficking of Na+/Ca2+ exchanger to the site of persistent inflammation in nociceptive afferents

Persistent inflammation results in an increase in the amplitude and duration of depolarization-evoked Ca(2+) transients in putative nociceptive afferents. Previous data indicated that these changes were the result of neither increased neuronal excitability nor an increase in the amplitude of depolarization. Subsequent data also ruled out an increase in voltage-gated Ca(2+) currents and recruitment of Ca(2+)-induced Ca(2+) release. Parametric studies indicated that the inflammation-induced increase in the duration of the evoked Ca(2+) transient required a relatively large and long-lasting increase in the concentration of intracellular Ca(2+) implicating the Na(+)/Ca(2+) exchanger (NCX), a major Ca(2+) extrusion mechanism activated with high intracellular Ca(2+) loads. The contribution of NCX to the inflammation-induced increase in the evoked Ca(2+) transient in rat sensory neurons was tested using fura-2 AM imaging and electrophysiological recordings. Changes in NCX expression and protein were assessed with real-time PCR and Western blot analysis, respectively. An inflammation-induced decrease in NCX activity was observed in a subpopulation of putative nociceptive neurons innervating the site of inflammation. The time course of the decrease in NCX activity paralleled that of the inflammation-induced changes in nociceptive behavior. The change in NCX3 in the cell body was associated with a decrease in NCX3 protein in the ganglia, an increase in the peripheral nerve (sciatic) yet no change in the central root. This single response to inflammation is associated with changes in at least three different segments of the primary afferent, all of which are likely to contribute to the dynamic response to persistent inflammation.

Controlling potassium selectivity and proton blocking in a hybrid biological/solid-state polymer nanoporous membrane

Specific separations of protons and cations are usually performed by electromembrane processes, which require external electric energy. An easier process would be using a membrane able to separate both entities by passive diffusion. Presently, such synthetic nanoporous membranes do not exist. Here, we report the production of a robust hybrid biological/artificial solid-state membrane, which allows selective permeation of alkali metal cations without competing or concurrent permeation of protons. This membrane is simple to prepare and is based on the hydrophobic nature of the polymeric pore walls, and the confined gramicidin A molecules within. This work opens a new route for separation in the domain of nanobiofiltration, especially for tunable nanodevices based on differential ion conduction, with a fundamental understanding of the confinement mechanism.

Calibration procedures for the quantitative determination of membrane potential in human cells using anionic dyes

Quantitative determinations of the cell membrane potential of lymphocytes (Wilson et al., J Cell Physiol 1985;125:72-81) and thymocytes (Krasznai et al., J Photochem Photobiol B 1995;28:93-99) using the anionic dye DiBAC4 (3) proved that dye depletion in the extracellular medium as a result of cellular uptake can be negligible over a wide range of cell densities. In contrast, most flow cytometric studies have not verified this condition but rather assumed it from the start. Consequently, the initially prepared extracellular dye concentration has usually been used for the calculation of the Nernst potential of the dye. In this study, however, external dye depletion could be observed in both large IGR-1 and small LCL-HO cells under experimental conditions, which have often been applied routinely in spectrofluorimetry and flow cytometry. The maximum cell density at which dye depletion could be virtually avoided was dependent on cell size and membrane potential and definitely needed to be taken into account to ensure reliable results. In addition, accepted calibration procedures based on the partition of sodium and potassium (Goldman-Hodgkin-Katz equation) or potassium alone (Nernst equation) were performed by flow cytometry on cell suspensions with an appropriately low cell density. The observed extensive lack of concordance between the correspondingly calculated membrane potential and the equilibrium potential of DiBAC4 (3) revealed that these methods require the additional measurement of cation parameters (membrane permeability and/or intracellular concentration). In contrast, due to the linear relation between fluorescence and low DiBAC4 (3) concentrations, the Nernst potential of the dye for totally depolarized cells can be reliably used for calibration with an essentially lower effort and expense.

Steady-state solutions of cell volume in a cardiac myocyte model elaborated for membrane excitation, ion homeostasis and Ca2+ dynamics

The cell volume continuously changes in response to varying physiological conditions, and mechanisms underlying volume regulation have been investigated in both experimental and theoretical studies. Here, general formulations concerning cell volume change are presented in the context of developing a comprehensive cell model which takes Ca(2+) dynamics into account. Explicit formulas for charge conservation and steady-state volumes of the cytosol and endoplasmic reticulum (ER) are derived in terms of membrane potential, amount of ions, Ca(2+)-bound buffer molecules, and initial cellular conditions. The formulations were applied to a ventricular myocyte model which has plasma-membrane Ca(2+) currents with dynamic gating mechanisms, Ca(2+)-buffering reactions with diffusive and non-diffusive buffer proteins, and Ca(2+) uptake into or release from the sarcoplasmic reticulum (SR) accompanied by compensatory cationic or anionic currents through the SR membrane. Time-dependent volume changes in cardiac myocytes induced by varying extracellular osmolarity or by action potential generation were successfully simulated by the novel formulations. Through application of bifurcation analysis, the existence and uniqueness of steady-state solutions of the cell volume were validated, and contributions of individual ion channels and transporters to the steady-state volume were systematically analyzed. The new formulas are consistent with previous fundamental theory derived from simple models of minimum compositions. The new formulations may be useful for examination of the relationship between cell function and volume change in other cell types.

Acupuncture reduces crying in infants with infantile colic: a randomised, controlled, blind clinical study

OBJECTIVE

To investigate whether acupuncture reduces the duration and intensity of crying in infants with colic. Patients and methods 90 otherwise healthy infants, 2-8 weeks old, with infantile colic were randomised in this controlled blind study. 81 completed a structured programme consisting of six visits during 3 weeks to an acupuncture clinic in Sweden. Parents blinded to the allocation of their children met a blinded nurse. The infant was subsequently given to another nurse in a separate room, who handled all infants similarly except that infants allocated to receive acupuncture were given minimal, standardised acupuncture for 2 s in LI4.

RESULTS

There was a difference (p=0.034) favouring the acupuncture group in the time which passed from inclusion until the infant no longer met the criteria for colic. The duration of fussing was lower in the acupuncture group the first (74 vs 129 min; p=0.029) and second week (71 vs 102 min; p=0.047) as well as the duration of colicky crying in the second intervention week (9 vs 13 min; p=0.046) was lower in the acupuncture group. The total duration of fussing, crying and colicky crying (TC) was lower in the acupuncture group during the first (193 vs 225 min; p=0.025) and the second intervention week (164 vs 188 min; p=0.016). The relative difference from baseline throughout the intervention weeks showed differences between groups for fussing in the first week (22 vs 6 min; p=0.028), for colicky crying in the second week (92 vs 73 min; p=0.041) and for TC in the second week (44 vs 29 min; p=0.024), demonstrating favour towards the acupuncture group.

CONCLUSIONS

Minimal acupuncture shortened the duration and reduced the intensity of crying in infants with colic. Further research using different acupuncture points, needle techniques and intervals between treatments is required.

Synaptotoxicity of Alzheimer beta amyloid can be explained by its membrane perforating property

The mechanisms that induce Alzheimer's disease (AD) are largely unknown thereby deterring the development of disease-modifying therapies. One working hypothesis of AD is that Aβ excess disrupts membranes causing pore formation leading to alterations in ionic homeostasis. However, it is largely unknown if this also occurs in native brain neuronal membranes. Here we show that similar to other pore forming toxins, Aβ induces perforation of neuronal membranes causing an increase in membrane conductance, intracellular calcium and ethidium bromide influx. These data reveal that the target of Aβ is not another membrane protein, but that Aβ itself is the cellular target thereby explaining the failure of current therapies to interfere with the course of AD. We propose that this novel effect of Aβ could be useful for the discovery of anti AD drugs capable of blocking these “Aβ perforates”. In addition, we demonstrate that peptides that block Aβ neurotoxicity also slow or prevent the membrane-perforating action of Aβ.

Functional magnetic resonance imaging activation of the brain in children: real acupoint versus sham acupoint

The purpose was to examine the brain activation patterns with acupuncture using real acupoint (Liv3) versus sham acupoint in healthy, sedated children using functional magnetic resonance imaging (fMRI). Functional magnetic resonance imaging scans of the brain for 10 healthy, sedated children were taken during stimulation of real acupoint (Liv3 [Taichong]) and a nearby sham acupoint in a randomized order, employing twisting and nontwisting methods using a blocked paradigm using a 2.0-T scanner. The functional data were analyzed by using SPM 99. Various regions of the brain were activated in 2 acupoints. However, the pattern was different for the 2 acupoints. We suggest specific cerebral activation patterns with acupuncture might explain some of its therapeutic effect.

THE TREATMENT OF OBESITY BY ACUPUNCTURE

The present study is an investigation of the results of the studies on the effects of acupuncture application therapy on obesity. It has been reported that acupuncture application in obesity treatment is effective in procuring weight loss. It can affect appetite, intestinal motility, and metabolism, as well as emotional factors such as stress. Increases in neural activity in the ventromedial nuclei of the hypothalamus, in tone in the smooth muscle of the stomach and in levels of enkephalin, beta endorphin, and serotonin in plasma and brain tissue have also been observed with the application of acupuncture. It has been observed that acupuncture application to obese people increases excitability of the satiety center in the ventromedial nuclei of the hypothalamus. Acupuncture stimulates the auricular branch of the vagal nerve and raises serotonin levels. Both of these activities have been shown to increase tone in the smooth muscle of the stomach, thus suppressing appetite. Among other things, serotonin enhances intestinal motility. It also controls stress and depression via endorphin and dopamine production. In addition to these effects, it is thought that the increase in plasma levels of beta endorphin after acupuncture application can contribute to the body weight loss in obese people by mobilizing the body energy depots through lipolithic effect.

Different effects of electroacupuncture on esophageal motility and serum hormones in cats with esophagitis

We aim to investigate the effects of different electroacupuncture (EA) frequencies at ST-36 on esophageal motility, and to compare the effect of EA on serum gastrin (GAS), motilin (MTL), and vasoactive intestinal peptide (VIP). Thirty-two cats were divided into four equal groups. All animals underwent a Heller myotomy. After esophagitis developed two frequencies (2/15 Hz or 2/100 Hz) of EA were delivered into ST-36 (LEA group [low EA], HEA group [high EA]). Animals submitted to EA on a non-point region (EANP) were used as controls (LEANP group, HEANP group), respectively. Esophageal motility was continuously monitored. The lower esophageal sphincter pressure (LESP) decreased significantly after myotomy. The LESP decreased in both LEA and LEANP cats, and in LEA cats the pressure decrease was greater. The LESP increased in the HEA group, which was higher than that in the HEANP group (P < 0.05). High-frequency EA significantly increased the peak amplitude in esophageal peristalsis. There was a decrease in serum GAS and MTL in LEA cats compared with LEANP cats (both P < 0.01). GAS and MTL were higher in the HEA group than in the HEANP group (both P < 0.01). Serum VIP decreased in the HEA group (P < 0.05), while it increased in the LEA group (P < 0.05), compared with EANP groups, respectively. EA with a high frequency at ST-36 enhances LESP as well as esophageal motility, while EA with a low frequency decreases LESP. The effect of EA is acupoint-specific, and this effect appears to be mediated through GAS, MTL and VIP.

Autocrine activation of ion currents in the two-cell mouse embryo

The actions of autocrine ligands are required for the normal development of the preimplantation embryo in vitro. These ligands act as survival factors for the preimplantation stage embryo. One autocrine ligand, paf (1-o-alkyl-2-acetyl-sn-gylcero-3-phosphocholine), induced a dihydropyridine-sensitive calcium transient in the zygote and two-cell embryo, and these transients were required for the normal preimplantation stage survival. Paf induces an influx of external calcium through a dihydropyridine-sensitive channel. Dihydropyridine-sensitive currents are voltage-regulated, yet to date there is no evidence of membrane voltage depolarization in the two-cell embryo. To define the paf-induced calcium influx we have examined the response of the membrane potential and ion currents to paf in two-cell embryos. An initial response to paf challenge was the expression of an ion current (-15.6+/-1.6 pA) that was dependent upon extracellular calcium, was not voltage-gated but was dihydropyridine (nifedipine)-sensitive. This calcium current was followed (91+/-6 s after paf) by a net outward current (284+/-59 pA) that was composed of 4,4'-diisothiocyanatostilbene-2,2'-disulfonate-sensitive (anion channel blocker) and tetraethylammonium chloride-sensitive (K(+) channel blocker) currents. This current corresponded temporally with a marked paf-induced transient hyperpolarization of the membrane potential (-8.4+/-1.2 mV) that was dependent upon the generation of the calcium transient. The results directly demonstrate the activation of a voltage-independent calcium current in response to paf and show for the first time the expression of an afterhyperpolarization that occurs as a response to the calcium transient.

Acupuncture for Perimenopausal Symptoms in Women who Underwent Oophorectomy – a Comparative Study

OBJECTIVE

To explore the effects of acupuncture on perimenopausal symptoms in women who underwent oophorectomy.

METHODS

67 women who had undergone oophorectomy were divided into an acupuncture group (n = 36) and a comparison group (n = 31) according to their wishes. The first group was treated by acupuncture and the latter group by Livial. Clinical symptoms were assessed by the modified Kupperman index. The levels of venous blood serum beta-endorphin (beta-EP), follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and the maturation index (MI) of vaginal epithelial cells were assessed.

RESULTS

There were no significant group differences for the MI of vaginal exfoliative cells nor for the levels of FSH, LH and E2 after treatment (p > 0.05), but Kupperman scoring and the levels of beta-EP differed significantly between the acupuncture and the Livial group (p < 0.05). No side-effects were reported in either group.

CONCLUSION

Acupuncture results in a significant improvement in perimenopausal symptoms in women who have had an oophorectomy. Acupuncture performs as well or better than Livial. Yet, this result may have been influenced by a potential bias and the small sample size.

Acupuncture for functional gastrointestinal disorders

Functional gastrointestinal (GI) symptoms are common in the general population. Especially, motor dysfunction of the GI tract and visceral hypersensitivity are important. Acupuncture has been used to treat GI symptoms in China for thousands of years. It is conceivable that acupuncture may be effective in patients with functional GI disorders because it has been shown to alter acid secretion, GI motility, and visceral pain. Acupuncture at the lower limbs (ST-36) causes muscle contractions via the somatoparasympathetic pathway, while at the upper abdomen (CV-12) it causes muscle relaxation via the somatosympathetic pathway. In some patients with gastroesophageal reflux disease (GERD) and functional dyspepsia (FD), peristalsis and gastric motility are impaired. The stimulatory effects of acupuncture at ST-36 on GI motility may be beneficial to patients with GERD or FD, as well as to those with constipation-predominant irritable bowel syndrome (IBS), who show delayed colonic transit. In contrast, the inhibitory effects of acupuncture at CV-12 on GI motility may be beneficial to patients with diarrhea-predominant IBS, because enhanced colonic motility and accelerated colonic transit are reported in such patients. Acupuncture at CV-12 may inhibit gastric acid secretion via the somatosympathetic pathway. Thus, acupuncture may be beneficial to GERD patients. The antiemetic effects of acupuncture at PC-6 (wrist) may be beneficial to patients with FD, whereas the antinociceptive effects of acupuncture at PC-6 and ST-36 may be beneficial to patients with visceral hypersensitivity. In the future, it is expected that acupuncture will be used in the treatment of patients with functional GI disorders.

Intracellular and extracellular concentrations of Na+ modulate Mg2+ transport in rat ventricular myocytes

Apparent free cytoplasmic concentrations of Mg2+ ([Mg2+]i) and Na+ ([Na+]i) were estimated in rat ventricular myocytes using fluorescent indicators, furaptra (mag-fura-2) for Mg2+ and sodium-binding benzofuran isophthalate for Na+, at 25 degrees C in Ca2+-free conditions. Analysis included corrections for the influence of Na+ on furaptra fluorescence found in vitro and in vivo. The myocytes were loaded with Mg2+ in a solution containing 24 mM Mg2+ either in the presence of 106 mM Na+ plus 1 mM ouabain (Na+ loading) or in the presence of only 1.6 mM Na+ to deplete the cells of Na+ (Na+ depletion). The initial rate of decrease in [Mg2+]i from the Mg2+-loaded cells was estimated in the presence of 140 mM Na+ and 1 mM Mg2+ as an index of the rate of extracellular Na+-dependent Mg2+ efflux. Average [Na+]i, when estimated from sodium-binding benzofuran isophthalate fluorescence in separate experiments, increased from 12 to 31 mM and 47 mM after Na+ loading for 1 and 3 h, respectively, and decreased to approximately 0 mM after 3 h of Na+ depletion. The intracellular Na+ loading significantly reduced the initial rate of decrease in [Mg2+]i, on average, by 40% at 1 h and by 64% at 3 h, suggesting that the Mg2+ efflux was inhibited by intracellular Na+ with 50% inhibition at approximately 40 mM. A reduction of the rate of Mg2+ efflux was also observed when Na+ was introduced into the cells through the amphotericin B-perforated cell membrane (perforated patch-clamp technique) via a patch pipette that contained 130 mM Na+. When the cells were heavily loaded with Na+ with ouabain in combination with intracellular perfusion from the patch pipette containing 130 mM Na+, removal of extracellular Na+ caused an increase in [Mg2+]i, albeit at a very limited rate, which could be interpreted as reversal of the Mg2+ transport, i.e., Mg2+ influx driven by reversed Na+ gradient. Extracellular Na+ dependence of the rate of Mg2+ efflux revealed that the Mg2+ efflux was activated by extracellular Na+ with half-maximal activation at 55 mM. These results contribute to a quantitative characterization of the Na+-Mg2+ exchange in cardiac myocytes.

Effects of electroacupuncture on gastric myoelectrical activity in healthy humans

The acupuncture point of the wrists (PC6) and the lower legs (ST36) are common points for the treatment of gastric symptoms. However, it remains unclear whether these two acupoints have different effects on gastric myoelectrical activity. We compared the effect of electroacupuncture (EAP) between PC6 and ST36 on gastric myoelectrical activity using surface electrogastrography (EGG). EAP (1 Hz, for 30 min) was applied at either ST36, or PC6, or both acupoints in eight healthy volunteers. EAP at both PC6 and ST36 did not change the percentage of normal slow waves and tachygastria. While EAP at either PC6 or ST36 did not change period dominant frequency (PDF), EAP at both PC6 and ST36 significantly decreased PDF to 78.1 +/- 8.4% of baselines. EAP at PC6 reduced period dominant power (PDP) to 47.2 +/- 5.3% of baselines, while EAP at ST36 increased PDP to 153.6 +/- 28.3% of baselines. EAP at shoulders (sham acupuncture) did not affect the gastric myoelectrical activity. EAP at either PC6 or ST36 shows an opposite effect on PDP, whereas EAP at both PC6 and ST36 has a synergistic effect on PDF. Understanding site-specific effects of acupuncture may contribute to the selection of appropriate acupoints for treating functional GI disorders.

Cell-Volume Regulation by Swelling-Activated Chloride Current in Guinea-Pig Ventricular Myocytes

The cell-volume regulation by swelling-activated Cl- current (I(Cl,swell)) was studied in guinea pig ventricular myocytes, using a microscopic video-image analysis. We have previously shown that in ventricular cells depolarized in high-K+ ([K+]o>45 mM) solution, an activation of the cyclic AMP-dependent Cl- current (I(Cl,cAMP)) leads to cell swelling. We first investigated the mechanism underlying the I(Cl,cAMP)-independent recovery (shrinkage) of the swollen cells. They shrank when the membrane potential (Vm) was made negative to the equilibrium potential of Cl- (ECl) by lowering [K+]o or [Cl-]o in the high-K+ solution. This shrinkage was attenuated by the inhibitors (DIDS, glibenclamide, furosemide) of swelling-activated Cl- current (I(Cl,swell)). These findings suggested an involvement of I(Cl,swell) in the observed isosmotic cell shrinkage. On the other hand, an application of hyposmotic (70% of control) solution to the cells at normal [K+]o (ECl>Vm) induced a cell swelling, and the swollen cells underwent a slight but definite spontaneous cell shrinkage during hyposmotic challenge, indicating the operation of the mechanism of regulatory volume decrease (RVD). This RVD was pronounced at low [Cl-]o, at which ECl was much more positive than Vm. On the contrary, when the hyposmotic solution was applied to the cells at high [K+]o, at which ECl was negative to Vm, the cells swelled vigorously and monotonically without showing RVD, the swelling being much greater than that seen at normal [K+]o. Both the RVD at normal [K+]o and the extra cell swelling at high [K+]o were suppressed by DIDS. These results suggest that I(Cl,swell) activated by cell swelling can shrink or inflate the cardiac cells under hyposmotic as well as isosmotic conditions, depending on Vm and ECl.

Comparison of electroacupuncture and butorphanol on respiratory and cardiovascular effects and rectal pain threshold after controlled rectal distention in mares

OBJECTIVE

To compare effects of electroacupuncture and butorphanol on hemodynamic and respiratory variables and rectal analgesia in mares after controlled rectal distention.

ANIMALS

8 healthy mares.

PROCEDURE

Each horse received saline (0.9% NaCl) solution (0.01 mL/kg, IV; control treatment), butorphanol tartrate (0.1 mg/kg, IV), or 2 hours of electroacupuncture (EA) at acupoints Bladder 21, 25, and 27 on both sides of the vertebral column, Bai hui, and Stomach 36 (right side only). Order of treatments in each mare was randomized. At least 7 days elapsed between treatments. A balloon was inserted in the rectum of each mare, and controlled distention of the balloon (pressures of < or = 220 mm Hg) was used to measure nociceptive rectal pain threshold. Rectal temperature and cardiovascular and respiratory variables were measured before (baseline) and 5,15, 30, 60, 90, and 120 minutes after onset of each treatment.

RESULTS

Butorphanol produced greater increases in rectal pain threshold, compared with EA (mean +/- SD, 214 +/- 24 vs 174 +/- 35 mm Hg of balloon pressure). Electroacupuncture produced minimal cardiovascular and respiratory changes. Although clinically not important, butorphanol produced moderate significant increases in heart and respiratory rates, arterial blood pressure, and rectal temperature and decreases in arterial oxygen tension. Arterial pH, carbon dioxide tension, bicarbonate concentrations, base excess, Hct, and concentration of total solids were not significantly different from baseline values after EA, butorphanol, and control treatments.

CONCLUSIONS AND CLINICAL RELEVANCE

Electroacupuncture and butorphanol (0.1 mg/kg, IV) may provide useful rectal analgesia in horses.

Plasmalemmal KATP channels shape triggered calcium transients in metabolically impaired rat atrial myocytes

The relative role of plasmalemmal and mitochondrial ATP-sensitive K(+) (K(ATP)) channels in calcium homeostasis of the atrium is little understood. Electrically triggered (1 Hz) cytoplasmic calcium transients were measured by 340-to-380-nm wavelength fura 2 emission ratios in cultured rat atrial myocytes. CCCP, a mitochondrial protonophore (100-400 nmol/l), dose dependently reduced the transient amplitude by up to 85%, caused a slow rise in baseline calcium, and reduced the recovery time constant of the transient from 143 to 91 ms (P < 0.05). However, neither 5-hydroxydecanoate, a mitochondrial K(ATP) channel blocker, nor diazoxide (500 micromol/l) affected the amplitude, baseline, or time constant in CCCP-treated cells. HMR-1098 (30 micromol/l), a plasmalemmal K(ATP) channel blocker, and glibenclamide (1 micromol/l) increased the amplitude in CCCP-treated myocytes by 69-82%, sharply elevated the calcium baseline, and prolonged the recovery time constant to 181-193 ms (P < 0.01). Thus opening of plasmalemmal but not mitochondrial K(ATP) channels reduces the calcium overload in metabolically compromised but otherwise intact atrial myocytes. Mitochondrial K(ATP) channels probably operate through a different mechanism to afford ischemic protection.

ATP and UTP excite sensory neurons and induce CREB phosphorylation through the metabotropic receptor, P2Y2

Extracellular ATP rapidly excites nociceptive sensory neurons by opening ATP-gated ion channels (P2X receptors). Here, we describe two actions of both ATP and UTP on rat sensory neurons that are relatively slow and sustained: phosphorylation of the transcription factor CREB and delayed action potential firing that persists for tens of seconds after removal of the ligand. The pharmacology of these responses indicates that they are mediated by the metabotropic receptor P2Y2, and not by P2X receptors. CREB phosphorylation occurred in a subset of small peripherin-positive neurons likely to be unmyelinated nociceptors. In situ hybridization analysis revealed widespread expression of P2Y2 mRNA in sensory neurons. CREB phosphorylation is mediated by both action-potential-evoked calcium influx and calcium release from intracellular stores. These findings suggest that P2Y2 contributes to the transduction of ATP-mediated sensory signalling, and may be involved in the activity-dependent regulation of nociceptor phenotype.

Inward rectifier K(+) current under physiological cytoplasmic conditions in guinea-pig cardiac ventricular cells

The outward current that flows through the strong inward rectifier K(+) (K(IR)) channel generates I(K1), one of the major repolarizing currents of the cardiac action potential. The amplitude and the time dependence of the outward current that flows through K(IR) channels is determined by its blockage by cytoplasmic cations such as polyamines and Mg(2+). Using the conventional whole-cell recording technique, we recently showed that the outward I(K1) can show a time dependence during repolarization due to competition of cytoplasmic particles for blocking K(IR) channels. We used the amphotericin B perforated patch-clamp technique to measure the physiological amplitude and time dependence of I(K1) during the membrane repolarization of guinea-pig cardiac ventricular myocytes. In 5.4 mM K(+) Tyrode solution, the density of the current consisting mostly of the sustained component of the outward I(K1) was about 3.1 A F(-1) at around -60 mV. The outward I(K1) showed an instantaneous increase followed by a time-dependent decay (outward I(K1) transient) on repolarization to -60 to -20 mV subsequent to a 200 ms depolarizing pulse at +37 mV (a double-pulse protocol). The amplitudes of the transients were large when a hyperpolarizing pre-pulse was applied before the double-pulse protocol, whereas they were small when a depolarizing pre-pulse was applied. The peak amplitudes of the transients elicited using a hyperpolarizing pre-pulse were 0.36, 0.63 and 1.01 A F(-1), and the decay time constants were 44, 14 and 6 ms, at -24, -35 and -45 mV, respectively. In the current-clamp experiments, a phase-plane analysis revealed that application of pre-pulses changed the current density at the repolarization phase to the extents expected from the changes of the I(K1) transient. Our study provides the first evidence that an outward I(K1) transient flows during cardiac action potentials.

An exploratory pilot study of acupuncture on the quality of life and reproductive hormone secretion in menopausal women

The majority of menopausal women suffer from climacteric symptoms. The purpose of this study was to assess the effects of acupuncture on the quality of life and reproductive hormones secretion in menopausal women. Eleven (11) menopausal women with climacteric symptoms entered this prospective study. The Menopause Specific Quality of life Questionnaire was filled out by the patients before the first acupuncture session, after the last one (5 weeks later), and 3 months after the last acupuncture session. Reproductive hormones including follicular-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, progesterone, and prolactin were measured before and after treatment. Acupuncture significantly improved menopausal vasomotor symptoms (p = 0.001 and p = 0.003 for the end of treatment and 3 months later, respectively) and physical symptoms (p = 0.014 at the end of treatment and p = 0.046 3 months later). It did not change psychosocial or sexual symptoms, nor did it change the measured reproductive hormones. In conclusion, acupuncture is shown to be effective in relieving vasomotor and physical disturbances of menopausal women with effects lasting at least up to 3 months after termination of the treatment. Acupuncture may be a useful treatment alternative for women who are unable or do not want to receive hormone replacement therapy. A prospective study with larger sample sizes will be needed to define the role of acupuncture in the management of menopausal symptoms.

Synchronized Ca2+signals mediated by Ca2+action potentials in the hippocampal neuron network in vitro

Periodic, synchronized Ca2+ signals appeared 30-120 min after the application of tetrodotoxin, 4-aminopyridine and Cs+, and became stable in interval (6-47s) for hours. The Ca2+ signals were accompanied by excitatory or inhibitory postsynaptic potentials (excitatory postsynaptic currents (EPSCs) for the former) and blocked by the simultaneous application of 6-cyano-7-nitroquinoxaline-2,3-dione and 3-((RS)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid or treatment with Ca2+ -free solution, nicardipine, or omega-conotoxin MVIIC (omegaCTX), but not with ryanodine, caffeine, thapsigargin or CPP alone. Nicardipine largely, but omegaCTX less, blocked Ca2+ action potentials or voltage pulse-induced Ca2+ currents at the cell soma, while omegaCTX completely blocked autaptic EPSCs. Ca2+ signals within a neuron occurred almost simultaneously in the cell soma and all the processes (> 200 microm), while the latency between Ca2+ signals of neighbouring neurons varied over hundreds of ms like that of Ca2 action potential induction from EPSPs. Ca2+ signals propagated in random directions throughout neural circuits. Thus, when Na+ and K+ channels are blocked, Ca2+ action potentials spontaneously occur somewhere in a neuron, eventually propagate via the cell soma to the presynaptic terminals and activate excitatory synaptic transmission, causing synchronized Ca2+ signals. The results further suggest that the axon of hippocampal neurones have the potential ability to convey coded information via Ca2+ action potentials.

Changes in cell volume induced by activation of the cyclic amp-dependent chloride channel in guinea-pig cardiac myocytes

The effects of the activation of cyclic AMP-dependent Cl- current (ICl,cAMP) on cell volume were studied at various [K+]o under isosmotic conditions in guinea-pig ventricular myocytes. The area of the cell image obtained with videomicroscopy was used as an index of cell volume. I(Cl,cAMP) was activated by adrenaline (5.5 microM). Measurements of the membrane potential (Vm) were performed by the gramicidin-perforated patch-clamp method. At 5.4 mM [K+]o with low [Cl-]o, where Vm was negative to the predicted equilibrium potential of Cl- (ECl), adrenaline sizably decreased the cell area. At high [K+]o with normal [Cl-]o, where Vm was positive to ECl, adrenaline increased the cell area; at 145.4 mM [K+]o the cell area was increased to 110% of control on average (n = 22). The cells swollen in this manner shrank when [Cl-]o was reduced to a low level in the presence of adrenaline. The results indicate that the induction of Cl- influxes (outward I(Cl,cAMP)) or effluxes (inward I(Cl,cAMP)) can lead to a cell swelling or shrinkage, respectively. The addition of BaCl2 (1 mm), a blocker of K+ channels, attenuated the adrenaline-dependent cell swelling, supporting the view that Cl- fluxes must be accompanied by cofluxes of K+ ions to affect the cell volume. The adrenaline-dependent cell swelling was inhibited by antagonizing beta-adrenergic stimulation with acetylcholine or by blocking I(Cl,cAMP) channels with glibenclamide, confirming the involvement of I(Cl,cAMP) in the adrenaline response. The results show that the activation of I(Cl,cAMP) can shrink or inflate the cardiac cells under isosmotic conditions, depending on Vm and ECl.

Immunomodulatory effects of acupuncture in the treatment of allergic asthma: a randomized controlled study

OBJECTIVE

According to Traditional Chinese Medicine (TCM) acupuncture is a suitable treatment for complex chronic diseases such as bronchial asthma. In a randomized, controlled study we investigated immunologic effects of Chinese acupuncture on patients with allergic asthma.

PATIENTS AND METHODS

The effects of acupuncture treatment given according to the principles of TCM (TCM group, n = 20) were compared with those of acupuncture treatment using points not specific for asthma (control group, n = 18). All patients were treated 12 times for 30 minutes over a time period of 4 weeks. Patients' general well-being and several peripheral blood parameters (eosinophils, lymphocyte subpopulations, cytokines, in vitro lymphocyte proliferation) were determined before and after acupuncture treatment.

RESULTS

In the TCM group, significantly more patients indicated an improvement in general well-being (79% in the TCM group versus 47% in the control group; p = 0.049) after acupuncture treatment. The following changes were found in the TCM group: within the lymphocyte subpopulations the CD3+ cells (p = 0.005) and CD4+ cells (p = 0.014) increased significantly. There were also significant changes in cytokine concentrations: interleukin (IL)-6 (p = 0.026) and IL-10 (p = 0.001) decreased whereas IL-8 (p = 0.050) rose significantly. Additionally, the in vitro lymphocyte proliferation rate increased significantly (p = 0.035) while the number of eosinophils decreased from 4.4% to 3.3% after acupuncture (p > 0.05). The control group, however, showed no significant changes apart from an increase in the CD4+ cells (p = 0.012).

CONCLUSION

The results imply that asthma patients benefit from acupuncture treatment given in addition to conventional therapy. Furthermore, acupuncture performed in accordance with the principles of TCM showed significant immune-modulating effects.

The sigma-ligand (+)-pentazocine depresses M current and enhances calcium conductances in frog melanotrophs

Gramicidin-perforated patch clamp experiments and microfluorimetric measurements were performed to study the ionic mechanisms involved in the sigma-receptor-mediated stimulation of frog (Rana ridibunda) pituitary melanotrophs. The sigma-ligand (+)-pentazocine (50 microM) depressed a sustained outward K(+) current. The kinetic properties of this K(+) component, investigated by analyzing tail currents, were reminiscent of those of the M current (I(M)), with an activation threshold close to -60 mV, a -21-mV half-maximal activation potential, and two-component exponential deactivation kinetics at -90 mV. (+)-Pentazocine (20 microM) produced a 12-mV rightward shift of the activation curve and accelerated the deactivation rate of the tail current. It is also demonstrated that (+)-pentazocine (20 microM) reversibly increased both voltage-dependent calcium conductances and internal calcium level. Altogether, these results suggest that the sigma-receptor-induced modulation of I(M) and calcium currents likely underlies the increase of intracellular [Ca(2+)].

Chloride-sensitive nature of the histamine-induced Ca2+ entry in cultured human aortic endothelial cells

1. Whole-cell currents and intracellular Ca2+ concentration ([Ca2+]i) were recorded in cultured human aortic endothelial cells (HAECs) to study the mechanisms underlying Cl--sensitive Ca2+ entry. 2. In the absence of histamine the membrane potential ranged between -90 and +5 mV and showed bimodal distribution with peaks at -17.8 and -67.5 mV. 3. Histamine (1-100 microM) activated an outward current, followed by a sustained inward current at -50 mV. The reversal potential (Vrev) was more negative than -60 mV for the initial outward current, and approximately -30 mV for the sustained inward current with normal Tyrode solution and internal solution containing 30 mM Cl-. 4. Vrev of the sustained inward current was hardly affected by varying the external concentrations of K+, Na+ and Ca2+, but was greatly changed by varying the external Cl- concentration ([Cl-]o). The relationship between Vrev and log[Cl-]o showed a slope of -44.8 mV per tenfold increase of [Cl-]o. 5. The Cl- channel blockers 9-anthracene carboxylic acid (1 mM), N-phenylanthranilic acid (0.1 mM) and niflumic acid (0.1 mM) all depressed the histamine-induced inward current. The non-selective cation channel blocker Gd3+ (10 microM) was without effect on the current. 6. In the absence of histamine, [Ca2+]i was not affected by varying the membrane potential. During the continuous presence of histamine, however, hyperpolarization increased and depolarization decreased [Ca2+]i, indicating that Ca2+ entry through the plasma membrane was activated by histamine. 7. Vrev of the histamine-induced Cl- current, measured by the gramicidin-perforated patch clamp method, was -28.4 +/- 6.6 mV (n = 8), which gave an intracellular Cl- concentration of approximately 34 mM. Under the current clamp condition, the membrane potential varied from cell to cell in the control, but application of histamine induced either depolarization or hyperpolarization, depending on the membrane potential before histamine application, and the membrane potential became stable near the equilibrium potential for Cl-. 8. We conclude that the histamine-induced inward current is carried mainly by Cl-. Although Ca2+ entry was also activated, we consider that its amplitude was too small to be resolved by the patch clamp method. The Cl- current may play a functional role in the sustained [Ca2+]i elevation by providing a constant driving force for Ca2+ entry in the presence of histamine.

alpha1-Adrenergic activation of L-type Ca current in rat ventricular myocytes: perforated patch-clamp recordings

alpha1-Adrenergic stimulation has little effect on L-type Ca2+ channel current (ICa,L) in adult cardiac myocytes measured using conventional whole cell voltage-clamp techniques. In this study using perforated-patch techniques, we reevaluated the effect of alpha1-adrenergic stimulation on ICa,L in adult rat ventricular myocytes. Action potentials and ICa,L were examined in the presence of 1 microM nadolol, a beta-adrenergic antagonist, in myocytes internally dialyzed with Na+- and K+-free solutions (Cs+ and tetraethylammonium as substitutes). Phenylephrine (PE; 30 microM) increased the action potential duration measured at 25 and 70% of repolarization by 104 and 86%, respectively. In the perforated-patch configuration, PE elicited a transient decrease followed by a approximately 60% increase in ICa,L, whereas only the transient decrease in ICa,L was observed in myocytes when the conventional whole cell configuration was used. The PE-induced increase in ICa,L was reversibly blocked by 1 microM prazosin, an alpha1-adrenergic antagonist. These results suggest that alpha1-adrenergic stimulation enhances cardiac ICa,L and that obligatory intracellular mediators for this action are lost during whole cell recordings.

Swelling-activated potassium currents of Ehrlich ascites tumour cells

The K+ and Cl- currents activated by Ca2+-ionophore treatment or by hypotonic cell swelling have been studied in Ehrlich ascites tumour cells by the patch-clamp technique. A charybdotoxin-inhibitable K+ current was activated by increasing intracellular Ca2+ concentration. In contrast, the K+ current activated by cell swelling was insensitive to charybdotoxin as well as to apamin, suggesting that channels different from those sensitive to Ca2+ are responsible for regulatory volume adjustments in these cells. The magnitude of the K+ and Cl- currents activated by hypotonic challenge was markedly temperature-dependent, possibly reflecting the temperature-dependence of enzymes involved in the intracellular signalling of cell volume regulation.