Melatonin inhibits arrhythmias induced by increased late sodium currents in ventricular myocytes / 药学学报

Melatonin (Mel) has been shown to have cardioprotective effects, but its action on ion channels is unclear. In this experiment, we investigated the inhibitory effect of Mel on late sodium currents (INa.L) in mouse ventricular myocytes and the anti-arrhythmic effect at the organ level as well as its mechanism. The whole-cell patch clamp technique was applied to record the ionic currents and action potential (AP) in mouse ventricular myocytes while the electrocardiogram (ECG) and monophasic action potential (MAP) were recorded simultaneously in mouse hearts using a multichannel acquisition and analysis system. The results demonstrated that the half maximal inhibitory concentration (IC50) values of Mel on transient sodium current (INa.T) and specific INa.L opener 2 nmol·L-1 sea anemone toxins II (ATX II) increased INa.L were 686.615 and 7.37 μmol·L-1, respectively. Mel did not affect L-type calcium current (ICa.L), transient outward current (Ito), and AP. In addition, 16 μmol·L-1 Mel shortened ATX II-prolonged action potential duration (APD), suppressed ATX II-induced early afterdepolarizations (EADs), and significantly reduced the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF) in Langendorff-perfused mouse hearts. In conclusion, Mel exerted its antiarrhythmic effects principally by blocking INa.L, thus providing a significant theoretical basis for new clinical applications of Mel. Animal welfare and experimental process are in accordance with the regulations of the Experimental Animal Ethics Committee of Wuhan University of Science and Technology (2023130).

Potentiation of PIEZO2 mechanically-activated currents in sensory neurons mediates vincristine-induced mechanical hypersensitivity

Vincristine, a widely used chemotherapeutic agent for treating different cancer, often induces severe peripheral neuropathic pain. A common symptom of vincristine-induced peripheral neuropathic pain is mechanical allodynia and hyperalgesia. However, mechanisms underlying vincristine-induced mechanical allodynia and hyperalgesia are not well understood. In the present study, we show with behavioral assessment in rats that vincristine induces mechanical allodynia and hyperalgesia in a PIEZO2 channel-dependent manner since gene knockdown or pharmacological inhibition of PIEZO2 channels alleviates vincristine-induced mechanical hypersensitivity. Electrophysiological results show that vincristine potentiates PIEZO2 rapidly adapting (RA) mechanically-activated (MA) currents in rat dorsal root ganglion (DRG) neurons. We have found that vincristine-induced potentiation of PIEZO2 MA currents is due to the enhancement of static plasma membrane tension (SPMT) of these cells following vincristine treatment. Reducing SPMT of DRG neurons by cytochalasin D (CD), a disruptor of the actin filament, abolishes vincristine-induced potentiation of PIEZO2 MA currents, and suppresses vincristine-induced mechanical hypersensitivity in rats. Collectively, enhancing SPMT and subsequently potentiating PIEZO2 MA currents in primary afferent neurons may be an underlying mechanism responsible for vincristine-induced mechanical allodynia and hyperalgesia in rats. Targeting to inhibit PIEZO2 channels may be an effective analgesic method to attenuate vincristine-induced mechanical hypersensitivity.

Effects of propofol on glutamatergic neuronal activity in paraventricular thalamus / 药学学报

This study explored the effects of propofol on the activity of glutamatergic neurons in the paraventricular thalamus (PVT) and the underlying mechanisms at the molecular level using whole-cell patch-clamp techniques. Acute brain slices containing the PVT were obtained from 8 weeks old C57BL/6J mice. The electrophysiological characteristics of PVT neurons were recorded in current-clamp mode, then single-cell sequencing was used to identify neuronal types. The firing frequencies before, during, and after propofol or intralipid application were recorded as FB, FD and FW; and the membrane potentials were recorded as MPB and MPD. Picrotoxin (PTX) was used to block inhibitory gamma-aminobutyric acid type A (GABAA) receptors during the application of propofol at 10 μmol·L-1. Then, GABAA receptor-mediated spontaneous and miniature inhibitory postsynaptic currents (sIPSCs and mIPSCs) were recorded, and the effects of 10 μmol·L-1 propofol were investigated. The animal experiments were approved by the Medical Animal Administrative Committee of Shanghai Medical College Fudan University. The results showed that there were no significant differences in FB, FD and FW during intralipid and 2 μmol·L-1 propofol application. With propofol at 5, 10 and 20 μmol·L-1, FD decreased significantly when compared with FB, and FW increased significantly as compared with FD (P < 0.01). The inhibition degree of the three concentration groups was significantly different (P < 0.01). In addition, with propofol at 20 μmol·L-1, MPD hyperpolarized significantly (P < 0.01). In the presence of PTX, 10 μmol·L-1 propofol could not suppress the firing frequency of PVT glutamatergic neurons. Propofol at 10 μmol·L-1 prolonged the decay time of sIPSCs (P < 0.01) and mIPSCs (P < 0.05), and increased the amplitude (P < 0.01) of mIPSCs of PVT glutamatergic neurons. Together, these results indicate that propofol can inhibit the activity of PVT glutamatergic neurons in a concentration-dependent and reversible manner, and the effect is likely to be mediated by postsynaptic GABAA receptors.

Ferulic acid enhances insulin secretion by potentiating L-type Ca2+ channel activation / 中西医结合学报

OBJECTIVE@#To investigate the effect of ferulic acid, a natural compound, on pancreatic beta cell viability, Ca2+ channels, and insulin secretion.@*METHODS@#We studied the effects of ferulic acid on rat insulinoma cell line viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay. The whole-cell patch-clamp technique and enzyme-linked immunosorbent assay were also used to examine the action of ferulic acid on Ca2+ channels and insulin secretion, respectively.@*RESULTS@#Ferulic acid did not affect cell viability during exposures up to 72 h. The electrophysiological study demonstrated that ferulic acid rapidly and concentration-dependently increased L-type Ca2+ channel current, shifting its activation curve in the hyperpolarizing direction with a decreased slope factor, while the voltage dependence of inactivation was not affected. On the other hand, ferulic acid have no effect on T-type Ca2+ channels. Furthermore, ferulic acid significantly increased insulin secretion, an effect inhibited by nifedipine and Ca2+-free extracellular fluid, confirming that ferulic acid-induced insulin secretion in these cells was mediated by augmenting Ca2+ influx through L-type Ca2+ channel. Our data also suggest that this may be a direct, nongenomic action.@*CONCLUSION@#This is the first electrophysiological demonstration that acute ferulic acid treatment could increase L-type Ca2+ channel current in pancreatic β cells by enhancing its voltage dependence of activation, leading to insulin secretion.

Study of electrophysiological mechanism of dopamine inhibiting insulin secretion by Kv channels / 中国药理学通报

Aim To study the electrophysiological mechanism of dopamine inhibiting insulin secretion hv voltage-dependent potassium ( Kv) channels.Methods Islets and (3 cells were isolated from male SD rats.D,-like receptor agonist ( SKP38393), D2-like receptor agonist (Quinpirole) and antagonist (Epiclopride) were used according to the experiment.Insulin secretion was detected by insulin radioimmunoassay.Whole-cell j J patch-clamp technique was applied to detect Kv channel currents and action potential duration of p cells.Di- BAC4(3) staining was used to observe membrane potential.Results SKF38393 did not affect insulin secretion and the Kv channel currents.Quinpirole signifi cantly inhibited insulin secretion and increased Kv channel currents.Dopamine significantly inhibited insulin secretion, increased Kv channel currents and shortened action potential duration of p cells, which could be reversed by epiclopride.In addition, dopamine de-creased membrane potential of INS-1 cells.Conclusions Dopamine inhibits insulin secretion by acting on D2-like receptors, resulting in actived Kv channels, shortened action potential duration and decreased cell membrane potential.

The insulinotropic effects and its relevant mechanism of telmisartan in rats / 中国药理学通报

Aim To investigate the insulinotropic effect of telmisartan anrl the underlying electrophysiological mechanism.Methods Islets and cells were isolated from Wistar rats.Islets were incubated with drugs un¬der different conditions, then supernatant liquid was collected for insulin secretion.Intracellular Ca" + ( Ca'+ j) levels of (3-cells were measured by calcium imaging technology.Patch-clamp technology was ap¬plied to detect effects on voltage-gated potassium chan¬nel ( Kv ) , and voltage-gated calcium channel ( VGCC ).Results Not affecting insulin secretion un¬der low glucose condition, telmisartan dose-dependent- ly stimulated insulin secretion under high glucose con¬ dition, and stimulation was enhanced with increasing glucose concentration.Acute increases of Ca' + concentration were elicited by telmisartan under high glucose condition.Telmisartan decreased current den¬sity of Kv channel, and increased VGCC current densi¬ty.Conclusions Telmisartan enhanced Ca~+ ; lev¬els of p-cells through its action on Kv channel and VGCC, thereby amplifying glucose-stimulated insulin secretion.

Perfect cellular platform for electrophysiology:acutely isolated vagal ganglion neurons from adult canines / 中国药理学与毒理学杂志

OBJECTIVE To establish a platform of electrophysiology using vagal ganglion neurons (VGNs) isolated from adult canines. METHODS The VGNs were enzymatically isolated from adult canines of either gender and cultured under experimental conditions. Action potential (AP), repetitive firing, voltage-gated outward K+ currents (IK) and hyperpolarization-mediated inward currents (Ih) were recorded under current-and voltage-clamp configurations before and after treatment. RESULTS Analysis of AP waveform showed that ① inaddition to traditionally classified myelinated A- and unmyelinated C-types, myelinated Ah-types could also be identified in females rather than in males; ② step current depolarization evoked a stimulus intensity-dependent repetitive discharge, and to reach a similar firing frequency, the lowest stimulus intensity was required for A-types, a similar or slightly higher stimulus intensity was needed for Ah-types, and the highest stimulus intensity was required for C-types;③tetro?dotoxin significantly reduced the rate of depolarization and positively shifted the AP firing threshold of Ah-types, and iberiotoxin dramatically increased the neuroexcitability of Ah-types;④all tested neurons functionally expressed IK and Ih, and the current density for both channels on average was A-types>Ah-types>C-types; ⑤ although the distribution of afferent types of VGNs differed between males and females, the known difference in discharge profiles of A- and C-types isolated from male and female rats was not studied here. CONCLUSION The VGNs can be successfully isolated from adult canines, AP, IK and Ih can be recorded. The tight seal can be held for at least 30 min, which may be enough for pharmacological investigation.

Jingzhaotoxin-X, a gating modifier of Kv4.2 and Kv4. 3 potassium channels purified from the venom of the Chinese tarantula Chilobrachys jingzhao

The tarantula Chilobrachys jingzhao is one of the largest venomous spiders in China. In previous studies, we purified and characterized at least eight peptides from C. jingzhao venom. In this report, we describe the purification and characterization of Jingzhaotoxin-X (JZTX-X), which selectively blocks Kv4.2 and Kv4.3 potassium channels. Methods: JZTX-X was purified using a combination of cation-exchange HPLC and reverse-phase HPLC. The amino-acid sequence was determined by automated Edman degradation and confirmed by mass spectrometry (MS). Voltage-gated ion channel currents were recorded in HEK293t cells transiently transfected with a variety of ion channel constructs. In addition, the hyperalgesic activity of JZTX-X and the toxin´s effect on motor function were assessed in mice. Results: JZTX-X contained 31 amino acids, with six cysteine residues that formed three disulfide bonds within an inhibitory cysteine knot (ICK) topology. In whole-cell voltage-clamp experiments, JZTX-X inhibited Kv4.2 and Kv4.3 potassium channels in a concentration- and voltage-dependent manner, without affecting other ion channels (Kv1.1, 1.2, 1.3, 2.1, delayed rectifier potassium channels, high- and low-voltage-activated Ca2+ channels, and voltage-gated sodium channels Nav1.5 and 1.7). JZTX-X also shifted the voltage-dependent channel activation to more depolarized potentials, whereas extreme depolarization caused reversible toxin binding to Kv4.2 channels. JZTX-X shifted the Kv4.2 and Kv4.3 activities towards a resting state, since at the resting potential the toxin completely inhibited the channels, even in the absence of an applied physical stimulus. Intrathecal or intraplantar injection of JZTX-X caused a long-lasting decrease in the mechanical nociceptive threshold (hyperalgesia) but had no effect on motor function as assessed in the rotarod test. Conclusions: JZTX-X selectively suppresses Kv4.2 and Kv4.3 potassium channel activity in a concentration- and voltage-dependent manner and causes long-lasting mechanical hyperalgesia.(AU)

Etomidate reduces excitability of the neurons and suppresses the function of nAChR ventral horn in the spinal cord of neonatal rats / 南方医科大学学报

OBJECTIVE@#To investigate the effects of etomidate on electrophysiological properties and nicotinic acetylcholine receptors (nAChRs) of ventral horn neurons in the spinal cord.@*METHODS@#The spinal cord containing lumbosacral enlargement was isolated from 19 neonatal SD rats aged 7-12 days. The spinal cord were sliced and digested with papain (0.18 g/30 mL artificial cerebrospinal fluid) and incubated for 40 min. At the ventral horn, acute mechanical separation of neurons was performed with fire-polished Pasteur pipettes, and perforated patch-clamp recordings combined with pharmacological methods were employed on the adherent healthy neurons. In current-clamp mode, the spontaneous action potential (AP) of the ventral horn neurons in the spinal cord was recorded. The effects of pretreatment with different concentrations of etomidate on AP recorded in the ventral horn neurons were examined. In the voltage-clamp mode, nicotine was applied to induce inward currents in the ventral horn neurons, and the effect of pretreatment with etomidate on the inward currents induced by nicotine were examined with different etomidate concentrations, different holding potentials and different use time.@*RESULTS@#The isolated ventral horn neurons were in good condition with large diverse somata and intact processes. The isolated spinal ventral horn neurons (=21) had spontaneous action potentials, and were continuously perfused for 2 min with 0.3, 3.0 and 30.0 μmol/L etomidate. Compared with those before administration, the AP amplitude, spike potential amplitude and overshoot were concentration-dependently suppressed ( < 0.01), and spontaneous discharge frequency was obviously reduced ( < 0.01, =12). The APs of the other 9 neurons were completely abolished by etomidate at 3.0 or 30 μmol/L. At the same holding potential (VH=-70 mV), pretreatment with 0.3, 3.0 or 30.0 μmol/L etomidate for 2 min concentration-dependently suppressed the current amplitude induced by 0.4 mmol/L nicotine ( < 0.01, =7). At the holding potentials of - 30, - 50, and - 70 mV, pretreatment with 30.0 μmol/L etomidate for 2 min voltage-dependently suppressed the current amplitude induced by 0.4 mmol/L nicotine ( < 0.01, =6 for each holding potential). During the 6 min of 30.0 μmol/L etomidate pretreatment, the clamped cells were exposed to 0.4 mmol/L nicotine for 4 times at 0, 2, 4, and 6 min (each exposure time was 2 s), and the nicotinic current amplitude decreased gradually as the number of exposures increased. But at the same concentration, two nicotine exposures (one at the beginning and the other at the end of the 6 min pretreatment) resulted in a significantly lower inhibition rate compared with 4 nicotine exposures ( < 0.01, =6).@*CONCLUSIONS@#etomidate reduces the excitability of the spinal ventral neurons in a concentration-dependent manner and suppresses the function of nAChR in a concentration-, voltage-, and use-dependent manner.

Potentiation of the glycine response by serotonin on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis in mice

The lamina II, also called the substantia gelatinosa (SG), of the trigeminal subnucleus caudalis (Vc), is thought to play an essential role in the control of orofacial nociception. Glycine and serotonin (5-hydroxytryptamine, 5-HT) are the important neurotransmitters that have the individual parts on the modulation of nociceptive transmission. However, the electrophysiological effects of 5-HT on the glycine receptors on SG neurons of the Vc have not been well studied yet. For this reason, we applied the whole-cell patch clamp technique to explore the interaction of intracellular signal transduction between 5-HT and the glycine receptors on SG neurons of the Vc in mice. In nine of 13 neurons tested (69.2%), pretreatment with 5-HT potentiated glycine-induced current (I(Gly)). Firstly, we examined with a 5-HT₁ receptor agonist (8-OH-DPAT, 5-HT(1/7) agonist, co-applied with SB-269970, 5-HT₇ antagonist) and antagonist (WAY-100635), but 5-HT₁ receptor agonist did not increase IGly and in the presence of 5-HT₁ antagonist, the potentiation of 5-HT on I(Gly) still happened. However, an agonist (α-methyl-5-HT) and antagonist (ketanserin) of the 5-HT₂ receptor mimicked and inhibited the enhancing effect of 5-HT on I(Gly) in the SG neurons, respectively. We also verified the role of the 5-HT₇ receptor by using a 5-HT₇ antagonist (SB-269970) but it also did not block the enhancement of 5-HT on I(Gly). Our study demonstrated that 5-HT facilitated I(Gly) in the SG neurons of the Vc through the 5-HT₂ receptor. The interaction between 5-HT and glycine appears to have a significant role in modulating the transmission of the nociceptive pathway.

Effects of L-borneol on chloride channel and cell volume in human umbilical vein endothelial cells / 中国药理学通报

Aim To study the effects of L-borneol on the chloride channel and cell volume of human umbili-cal vein endothelial cells (HUVECs). Methods Whole-cell patch-clamp technique was used to record chloride currents. The expression of ClC-3 protein was down-regulated by siRNA interference technique. The cell volume was measured by dynamic image analysis. Results 20 nmol·L-1L-borneol significantly activa-ted chloride current in HUVEC (79.59 ± 4.90) pA/pF, which could be inhibited by chloride channel blockers,NPPB and DIDS. The outward current inhib-itory rate of NPPB was (95.57 ± 2.57)%, while that of DIDS was (97.28 ± 6.36)%. The chloride current activated by L-borneol significantly decreased after the silence of ClC-3 (27.03 ± 3.89) pA/pF. Cell volume was markedly reduced by L-borneol (14.38 ± 1.58)%,which was inhibited after NPPB appliance. Conclusion L-borneol can activate ClC-3 chloride channel in HUVECs, which induces Cl- outflow then cell volume decrease.

Role of oxytocin in neonatal rat hippocampal neurons after hypoxic-ische-mic injury / 中国病理生理杂志

AIM: To investigate whether oxytocin has neuroprotective effects on hippocampal CA 1 pyramidal neurons from neonatal rats exposed to hypoxic-ischemic brain injury and the underlying mechanisms.METHODS:An in vitro model of hypoxic-ischemic injury was used by exposing the brain slices to oxygen-glucose deprivation(OGD)solution. Acute dissociated brain slices(6~8 slices per rat)from 8 Sprague-Dawely rats of 7~10 d old were used.The slices were randomly divided into 4 groups: control group, OGD 20 min group, OGD 40 min group and OGD +oxytocin group.The effect of oxytocin on neuronal death was evaluated by TO-PRO-3 staining.Fresh brain slices from other 20 neonatal rats were divided into OGD group,OGD+oxytocin group,OGD+dVOT(oxytocin receptor antagonist)+oxytocin group,and OGD+bicucuclline(GABAAreceptor antagonist)+oxytocin group.The onset of anoxic depolarization in the hippocampal neurons treated with different drugs was recorded by whole-cell patch-clamp techniques.RESULTS: The results of TO-PRO-3 staining showed that neuronal deaths in hippocampal CA 1 area were increased over the prolonged OGD time.Oxyto-cin significantly reduced the hypoxic-ischemic deaths.Oxytocin dramatically prolonged the onset time of anoxic depolariza-tion after the application of OGD solution.Both dVOT and bicuculline blocked this effect.CONCLUSION: Oxytocin plays a neuroprotective role in neonatal rat hippocampal CA 1 pyramidal neurons by enhancing the inhibitory synaptic trans-mission via oxytocin receptors.Therefore,oxytocin is useful as a candidate for neuroprotective treatment after neonatal hy -poxic-ischemic brain injury.

Comparison of electrophysiological properties of two types of pre-sympathetic neurons intermingled in the hypothalamic paraventricular nucleus

The hypothalamic paraventricular nucleus (PVN) contains two types of neurons projecting to either the rostral ventrolateral medulla (PVN(RVLM)) or the intermediolateral horn (IML) of the spinal cord (PVN(IML)). These two neuron groups are intermingled in the same subdivisions of the PVN and differentially regulate sympathetic outflow. However, electrophysiological evidence supporting such functional differences is largely lacking. Herein, we compared the electrophysiological properties of these neurons by using patch-clamp and retrograde-tracing techniques. Most neurons (>70%) in both groups spontaneously fired in the cell-attached mode. When compared to the PVN(IML) neurons, the PVN(RVLM) neurons had a lower firing rate and a more irregular firing pattern (p < 0.05). The PVN(RVLM) neurons showed smaller resting membrane potential, slower rise and decay times, and greater duration of spontaneous action potentials (p < 0.05). The PVN(RVLM) neurons received greater inhibitory synaptic inputs (frequency, p < 0.05) with a shorter rise time (p < 0.05). Taken together, the results indicate that the two pre-sympathetic neurons differ in their intrinsic and extrinsic electrophysiological properties, which may explain the lower firing activity of the PVN(RVLM) neurons. The greater inhibitory synaptic inputs to the PVN(RVLM) neurons also imply that these neurons have more integrative roles in regulation of sympathetic activity.

Korean red ginseng excitation of paraventricular nucleus neurons via non-N-methyl-D-aspartate glutamate receptor activation in mice

It has been reported that Korean red ginseng (KRG), a valuable and important traditional medicine, has varied effects on the central nervous system, suggesting its activities are complicated. The paraventricular nucleus (PVN) neurons of the hypothalamus has a critical role in stress responses and hormone secretions. Although the action mechanisms of KRG on various cells and systems have been reported, the direct membrane effects of KRG on PVN neurons have not been fully described. In this study, the direct membrane effects of KRG on PVN neuronal activity were investigated by using a perforated patch-clamp in ICR mice. In gramicidin perforated patch-clamp mode, KRG extract (KRGE) induced repeatable depolarization followed by hyperpolarization of PVN neurons. The KRGE-induced responses were concentration-dependent and persisted in the presence of tetrodotoxin, a voltage sensitive Na+ channel blocker. The KRGE-induced responses were suppressed by 6-cyano-7-nitroquinoxaline-2,3-dione (10 µM), a non-N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, but not by picrotoxin, a type A gamma-aminobutyric acid receptor antagonist. The results indicate that KRG activates non-NMDA glutamate receptors of PVN neurons in mice, suggesting that KRG may be a candidate for use in regulation of stress responses by controlling autonomic nervous system and hormone secretion.

Change in hippocampal voltage-gated Ⅰ sodium channel of Lithium chloride-Pilocarpine epileptic rat model / 中华实用儿科临床杂志

Objective To research the changes in hippocampal voltage-gated sodium channel of Lithium chloride-Pilocarpine epileptic rat models,including Ⅰ sodium channel α subunit protein (Nav1.1),mRNA of Ⅰ sodium channel alpha subunit protein gene and function of sodium channel.Methods Epileptic rat models of Lithium chloride-Pilocarpine were established.Nav1.1 expression in the hippocampus of experimental rats was detected by immunohistochemical staining method,and the changes in voltage-gated sodium channel function (the current-voltage curves,activation and inactivation curves and the recovery curve) of hippocampus nerve cells were detected by whole cell patch-clamp technique.Results (1) The Lithium chloride-Pilocarpine rat models were successfully reproduced.Three stages of behavior (acute,latent and chronic) of rat models were observed.The blank control group was free of seizure.(2) Immunohistochemistry results:neurons in CA1 and DG regions of hippocampal of epileptic rats were normal,and there was no obvious change in the expression of Nav1.1.In CA3 area,the degeneration and necrosis of neurons were obvious.Staining of Nav1.1 became superficial and even disappeared in these areas,but the normal tissues were enhanced around degenerative and necrotic neurons.Compared with the blank control group,the expression of Nav1.1 in the model group was higher(0.235 ±0.008 vs.O.210 ±0.002),and there was statistically significant difference (t'=-7.426,P ＜ 0.05).(3) The whole-cell patch-clamp technique showed that the sodium current density of the model group increased significantly compared with that of the blank group [(-319.70 ± 28.24) pA/pF vs.(-229.06 ± 26.01) pA/pF,t =8.178,P ＜ 0.05],the threshold value of activation curve decreased (4.15 ± 0.80 vs.4.50 ±0.85,t =11.020,P ＜ 0.05),the threshold value of inactivation curve increased (7.47 ± 0.53 vs.6.24 ±0.31,t =6.940,P ＜ 0.05),and the recovery time after inactivation shortened [(1.36 ± 0.15) ms vs.(1.86 ± 0.21)ms,t =6.712,P ＜ 0.05],and there were all statistically significant differences.Conclusion Repeated seizures can lead to increase Nav1.1 compensatory expression of,and significantly increase sodium channel current density,while the threshold value of activation curve decreases,the threshold value of inactivation curve rises,and the recovery time after inactivation is shortened,which eventually leads to increased neuron excitability and is more likely to cause seizures.

An improved method for isolation of human atrial cardiomyocytes / 重庆医学

Objective To study an improved isolated method of single human atrial myocytes.Methods Enzyme digestion method was used to isolate single myocytes from human atrial and whole-cell patch clamp technique was used to record small conductance calcium activated potassium current.Results This method obtained a large number of atrial myocytes.The total amount of atrial myocytes in SR group was 320±30 while AF group was 230±20 and the difference was statistically significant(P<0.01).In this study,a large number of simple and striated single atrial myocytes were obtained,and a typical small-conductance calcium-activated potassium channel current was recorded on the isolated atrial myocytes.Conclusion The established isolated method is simple,stable and effective.We can acquire a large amount of single atrial myocytes with good quality.

Acepromazine inhibits hERG potassium ion channels expressed in human embryonic kidney 293 cells

The effects of acepromazine on human ether-à-go-go-related gene (hERG) potassium channels were investigated using whole-cell voltage-clamp technique in human embryonic kidney (HEK293) cells transfected with hERG. The hERG currents were recorded with or without acepromazine, and the steady-state and peak tail currents were analyzed for the evaluating the drug effects. Acepromazine inhibited the hERG currents in a concentration-dependent manner with an IC₅₀ value of 1.5 µM and Hill coefficient of 1.1. Acepromazine blocked hERG currents in a voltage-dependent manner between –40 and +10 mV. Before and after application of acepromazine, the half activation potentials of hERG currents changed to hyperpolarizing direction. Acepromazine blocked both the steady-state hERG currents by depolarizing pulse and the peak tail currents by repolarizing pulse; however, the extent of blocking by acepromazine in the repolarizing pulse was more profound than that in the depolarizing pulse, indicating that acepromazine has a high affinity for the open state of the channels, with a relatively lower affinity for the closed state of hERG channels. A fast application of acepromazine during the tail currents inhibited the open state of hERG channels in a concentration-dependent. The steady-state inactivation of hERG currents shifted to the hyperpolarized direction by acepromazine. These results suggest that acepromazine inhibits the hERG channels probably by an open- and inactivated-channel blocking mechanism. Regarding to the fact that the hERG channels are the potential target of drug-induced long QT syndrome, our results suggest that acepromazine can possibly induce a cardiac arrhythmia through the inhibition of hERG channels.

Relation between esophageal visceral hyperesthesia and expression of acid-sensing ion channel 1 in rats with reflux esophagitis / 中华消化杂志

Objective To explore the role of the visceral afferent nerve hyperesthesia and acid-sensing ion channel 1 (ASIC1) in rats with reflux esophagitis (RE).Methods Sixty male Sprague-Dawley rats were selected and animal model was established.Rats were divided into control group (n=20) and RE group (n=40).The esophageal mocosa biopsy were routinely performed in two groups.The esophageal specific DRG neurons were identified by 1,1'dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate tracing method and the whole-cell patch clamp assay was performed.The expression of ASIC1 in esophageal mucosa and thoracic spine cord three to five segments at protein level and mRNA level were detected by Western blotting and quantitative real time-polymerase chain reaction (qPCR).Two independent samples t test was performed for statistical analysis.Results The body weight of RE group was significantly lower than that of control group ((179.41±-16.38) g vs (290.75 ±-22.20) g),and the difference was statistically significant (t=17.090,P＜ 0.01).Esophageal basal cell hyperplasia,papillary elongation,vascular dialation and congestion,inflammatory cells infiltration were found in RE group rats.The results of whole-cell patchclamp showed depolarization of the resting potential of esophageal-specific DRG neurons of RE group was more significant than that of control group (-(46.20 ± 1.92) mV vs-(51.60 ± 1.52) mV),and the difference was statistically significant (t=4.930,P＜0.01).The threshold current of RE group was much lower than that of control group ((18.00±13.04) pAvs (80.00±12.25) pA),and the difference was statistically significant (t=7.750,P＜0.01).When stimulated with two to three times the threshold current,the frequency of action potential of RE group significantly increased (5.80 ±1.48 vs 3.00 ±1.58,10.60±2.30 vs 5.20±1.92),and the differences were statistically significant (t=2.890 and 4.030,both P＜0.01).The results of Western blotting indicated that the expression of ASIC1 in esophageal mucosa of RE group was significatly lower than that of control group (0.614±0.120 vs 0.976±0.283),and the difference was statistically significant (t =2.885,P＜ 0.05),while there was no statistically significant difference in the expression of ASIC1 in DRG between RE group and control group (0.804 ± 0.182 vs 1.032±0.316;t=1.528,P＞0.05).The results of qPCR showed that the expression of ASIC1 mRNA in esophageal mucosa of RE group was lower than that of control group (0.694 ± 0.118 vs 1.036 ±0.137),and the difference was statistically significant (t=4.642,P＜0.01).However there was no statistically significant difference in ASIC1 at mRNA level between RE group and control group (1.002± 0.074 vs 0.985±0.120;t=0.294,P＞0.05).Conclusion The sensitivity of esophageal visceral afferent nerve of rats in RE group increases and ASIC1 may negatively regulate the formation of esophageal visceral hypersensitivity.

Relation between esophageal visceral hyperesthesia and expression of acid-sensing ion channel 1 in rats with reflux esophagitis / 中华消化杂志

Objective To explore the role of the visceral afferent nerve hyperesthesia and acid-sensing ion channel 1 (ASIC1) in rats with reflux esophagitis (RE).Methods Sixty male Sprague-Dawley rats were selected and animal model was established.Rats were divided into control group (n=20) and RE group (n=40).The esophageal mocosa biopsy were routinely performed in two groups.The esophageal specific DRG neurons were identified by 1,1'dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate tracing method and the whole-cell patch clamp assay was performed.The expression of ASIC1 in esophageal mucosa and thoracic spine cord three to five segments at protein level and mRNA level were detected by Western blotting and quantitative real time-polymerase chain reaction (qPCR).Two independent samples t test was performed for statistical analysis.Results The body weight of RE group was significantly lower than that of control group ((179.41±-16.38) g vs (290.75 ±-22.20) g),and the difference was statistically significant (t=17.090,P＜ 0.01).Esophageal basal cell hyperplasia,papillary elongation,vascular dialation and congestion,inflammatory cells infiltration were found in RE group rats.The results of whole-cell patchclamp showed depolarization of the resting potential of esophageal-specific DRG neurons of RE group was more significant than that of control group (-(46.20 ± 1.92) mV vs-(51.60 ± 1.52) mV),and the difference was statistically significant (t=4.930,P＜0.01).The threshold current of RE group was much lower than that of control group ((18.00±13.04) pAvs (80.00±12.25) pA),and the difference was statistically significant (t=7.750,P＜0.01).When stimulated with two to three times the threshold current,the frequency of action potential of RE group significantly increased (5.80 ±1.48 vs 3.00 ±1.58,10.60±2.30 vs 5.20±1.92),and the differences were statistically significant (t=2.890 and 4.030,both P＜0.01).The results of Western blotting indicated that the expression of ASIC1 in esophageal mucosa of RE group was significatly lower than that of control group (0.614±0.120 vs 0.976±0.283),and the difference was statistically significant (t =2.885,P＜ 0.05),while there was no statistically significant difference in the expression of ASIC1 in DRG between RE group and control group (0.804 ± 0.182 vs 1.032±0.316;t=1.528,P＞0.05).The results of qPCR showed that the expression of ASIC1 mRNA in esophageal mucosa of RE group was lower than that of control group (0.694 ± 0.118 vs 1.036 ±0.137),and the difference was statistically significant (t=4.642,P＜0.01).However there was no statistically significant difference in ASIC1 at mRNA level between RE group and control group (1.002± 0.074 vs 0.985±0.120;t=0.294,P＞0.05).Conclusion The sensitivity of esophageal visceral afferent nerve of rats in RE group increases and ASIC1 may negatively regulate the formation of esophageal visceral hypersensitivity.