OBJECTIVEto investigate the effect of deoxypodophyllotoxin (DOP) on membrane potential of dorsal unpaired median neurons (DUM, neurons) and its correlation with sodium channel.

METHODSDUM neurons were labeled with DiBAC4(3). Laser scanning confocal microscope was used to monitor the changes of membrane potential at real time on these neurons that were treated with different concentrations of the DOP. The effect of sodium channel blocker tetrodotoxin (TTX) on the changes was also observed.

RESULTSmembrane potential depolarization induced by the DOP peaked at 5 min and became stabilized after 8min. After compared with fluorescence intensity without treatment, the normalized fluorescence intensity was 69.6 ± 3.0, 72.1 ± 2.7, 77.8 ± 3.6, 86.2 ± 3.1 in cells which were treated with 1, 5, 25, 125 micromol/L DOP, respectively. These numbers were significantly lower than those from untreated control cells (P < 0.01). When DUM neurons were co-incubated with 1 micromol/L TTX for 20 min, then treated with 25 micromol/L DOP, the intensity changed to 63.6 ± 5.4, which was similar to that of the control (P > 0.05). This indicated that the effect of DOP could be completely inhibited by TTX.

CONCLUSIONDOP induced membrane depolarization of DUM neurons in the range of 1 approximately 125 micromol/L and the sodium channel should be involved in this process.

Animals ; Cells, Cultured ; Ganglia, Invertebrate ; drug effects ; physiology ; Membrane Potentials ; drug effects ; physiology ; Neurons ; drug effects ; physiology ; Periplaneta ; drug effects ; physiology ; Podophyllotoxin ; analogs & derivatives ; pharmacology ; Sodium Channels ; metabolism

OBJECTIVETo investigate the effect of ketamine on the high-voltage-activated calcium currents (ICa(HVA)) in rat hippocampal neurons.

METHODSNeurons were cultured from Wistar rat hippocampus. ICa(HVA) was recorded using whole-cell patch clamp technique. After application with ketamine at different concentrations (10, 30, 100, 300, and 1000 μmol/L), the effect of ketamine on ICa(HVA) was evaluated.

RESULTSICa(HVA) was inhibited by ketamine in a concentration-dependent manner. Ketamine at 10 μmol/L showed no effect on ICa(HVA). Four concentrations of ketamine (30, 100, 300,and 1000 μmol/L) reduced the peak ICa(HVA) currents by (17.5 ∓ 4.5)%, (25.5 ∓ 6.9)%, (38.5 ∓ 4.1)%, and (42.3 ∓ 4.6)% respectively,with a mean half maximal inhibitory concentration of 68.2 μmol/L and Hill coefficient of 0.47. The maximal activation membrane potential was shifted to (5.3 ∓ 0.8) from (5.4 ∓ 0.9). The half maximal activation membrane potential of inactivation curve was shifted from(-26.7 ∓ 3.9) mV to(-32.8 ∓ 4.2) mV.

CONCLUSIONKetamine can remarkably inhibit calcium currents in the central neurons,which may explain at least partly the action of ketamine on central nervous system.

Animals ; Calcium Channels ; drug effects ; physiology ; Cells, Cultured ; Hippocampus ; drug effects ; physiology ; Ketamine ; pharmacology ; Membrane Potentials ; drug effects ; Neurons ; drug effects ; physiology ; Rats ; Rats, Wistar

AIMTo learn the electrophysiological interference of levofloxacin (LVFX) to heart in guinea pig.

METHODSHigh, moderate and low doses of LVFX were given to the anesthetic guinea pig via i.p., and QT interval span and corrected QT-interval span in the II leading lines of ECG were recorded and analyzed from 5 min to 360 min after the drug administration. Single ventricular myocytes were obtained and impacted by LVFX solution of different concentrations. Then delayed rectifier potassium currents (I(K)) on single cells were recorded with whole-cell patch clamp technique, and compared with control group(without impact of LVFX).

RESULTS(1) After the administration of LVFX, at the dose of 200 mg/kg. QT-interval span was significantly elongated, and the increasing rate is 19.38% +/- 3.15% (P < 0.05). While at the relatively lower doses of 50 mg/kg and 100 mg/kg, the elongation is of low/no significance (P > 0.05). (2) LVFX inhibited I(K) dose-dependently and time-dependently.

CONCLUSIONLVFX might prolong the QT-interval span by the mechanism of inhibiting I(K), which implies a potential risk in clinical application.

Animals ; Guinea Pigs ; Levofloxacin ; Membrane Potentials ; Myocytes, Cardiac ; drug effects ; physiology ; Ofloxacin ; pharmacology ; Patch-Clamp Techniques

The membrane permeability to potassium at a resting state is greater than to any other ions and the maintenance of resting membrane potential is largely dependent on K+ concentration of outside medium (Hodgkin and Horowicz 1959), i.e. an increase of K+ concentration of medium induces a depolarization, vice versa. However, on the contrary to this prediction, in some mammalian heart muscle a reduction of external K+ concentration induces a depolarization of membrane potential rather than a hyperpolarization (Vassalle 1965). In this study it was aimed to elucidate the possible mechanism of spontaneous depolarization induced by low external K+ in canine Purkinje fibers. The membrane potential was constantly recorded while components of cations in the bathing medium were replaced one by one by equimolar sucrose until the low K+ induced depolarization was blocked. The results are summarized as follows; The membrane potential of canine Purkinje fibers was spontaneously depolarized by low external K+, and the magnitude of depolarization was not affected by verapamil TEA, and a partial replacement of external Na+ and Ca2+ with choline chloride. But the membrane potential was hyperpolarized only when the all external cations were substitued with sucrose; and this hyperpolarization was disappeared again by substitution of sucrose with choline chloride. From these results, it may be concluded that the depolarization induced by low external K+ in canine Purkinje fibers is due to the nonspecific increase of membrane permeability to external cations and/or combinations with decreased K+ conductance.
Animal ; Dogs ; Guinea Pigs ; Heart/physiology* ; Membrane Potentials/drug effects* ; Papillary Muscles/physiology ; Potassium/pharmacology* ; Purkinje Fibers/physiology ; Rest

OBJECTIVETo study potassium currents in isolated Deiters' cells of guinea pig cochlea and explore possible function of potassium current in Deiters' cell.

METHODSThe whole cell patch clamp recording technique was used to study potassium currents of Deiters' cells in normal external solution and solutions with different K(+) concentrations. We also studied the effects on reversal potentials and outward potassium currents.

RESULTSIsolated Deiters' cells possess voltage dependent, outwardly rectifying ion channels, which are K(+) selective. 50 mmol/L K(+) and 150 mmol/L K(+) in external solution reduced I(K-max) from (10.06 +/- 2.2) nA (n = 13) in normal external solution to (6.43 +/- 1.67) nA (n = 6, P < 0.05) and (5.49 +/- 1.33) nA (n = 6, P < 0.05), respectively. While the amplitude of tailcurrents decreased from (468.76 +/- 61.76) pA in 5 mmol K(+) external solution to (224.74 +/- 35.89) pA (P < 0.05) in 50 mmol/L K(+) and to (-911.59 +/- 78.17) pA (P < 0.01) in 150 mmol/L K(+) external solution.

CONCLUSIONSOutwardly rectifying potassium in Deiters' cells could buffer extracellular K(+) in the small space between Deiters' cells and outer hair cells or neural fibers and participate in the diffusion of K(+) from endolymph to perilymph.

Animals ; Cochlea ; cytology ; drug effects ; physiology ; Dose-Response Relationship, Drug ; Guinea Pigs ; Membrane Potentials ; drug effects ; physiology ; Patch-Clamp Techniques ; Potassium ; pharmacology ; Potassium Channels ; physiology

AIMTo investigate the effects of bradykinin on voltage-dependent sodium channel currents in rat dorsal root ganglion neurons (DRG).

METHODSWhole-cell patch clamp technique was used to determine sodium channel current.

RESULTSBradykinin at 0.01 - 10.0 micromol/L dose dependently increased the frequency of repetitive firing of DRG. Bradykinin at 0.01 - 10.0 micromol/L dose dependently enhanced the TTX-R sodium current, and had no effect on TTX-S sodium current.

CONCLUSIONMechanism underlying the inflammation induced by bradykinin is related to the TTX-R sodium channel.

Action Potentials ; drug effects ; Animals ; Bradykinin ; pharmacology ; Ganglia, Spinal ; drug effects ; physiology ; Membrane Potentials ; drug effects ; Neurons ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Sodium Channels ; drug effects ; physiology

Isolated rabbit aortic ring with intact endothelial cell preparations precontracted with NE (10(-7) M) were relaxed by vanadate in a dose dependent manner (from 0.2 to 2 mM). Application of vanadate and ACh during the tonic phase of high K+(100 mM)-induced contraction showed a slight relaxation in contrast to that in NE-induced contraction, but sodium nitroprusside (10 microM) more effectively relaxed the aortic ring preparations in high K+ contraction than that of vanadate. Vanadate-induced relaxation in NE-contracted aortic rings was reversed by application of BaCl2 (50 microM) or glibenclamide (10 microM). Furthermore, Vanadate hyperpolarized membrane potential of smooth muscle cells in endothelium-intact aortic strips and this effect was abolished by application of glibenclamide. The above results suggest that vanadate release EDHF (Endothelium-Derived Hyperpolarizing Factor), in addition to EDRF (Endothelium-Derived Relaxing Factor) from endothelial cell. This EDHF hyperpolarize the smooth muscle cell membrane potential via opening of the ATP-sensitive K+ channel and close a voltage dependent Ca++ channel. So it is suggested that the vanadate-induced relaxation of rabbit thoracic aortic rings may be due to the combined effects of EDRF and EDHF.
Animal ; Aorta/drug effects/physiology ; In Vitro ; Membrane Potentials/drug effects ; Potassium/pharmacology ; Potassium Channels/physiology ; Rabbits ; Support, Non-U.S. Gov't ; Tetraethylammonium Compounds/pharmacology ; Vanadates/*pharmacology ; Vasodilation/*drug effects

OBJECTIVETo study the damage of mitochondrial function of sperm induced by reactive oxygen species (ROS), and the protection of melatonin (MLT) against the damage.

METHODSSpermatozoa of normal physiological function selected from semen samples by Percoll gradient centrifugation technique were used as normal sperm models in the present study. Reactive oxygen species were generated by hypoxanthine xanthine oxidase system, and in the presence (or absence) of MLT (6 mmol/L), incubated with normal sperm models for 30 and 60 minutes. After incubation, the activity of succinate dehydrogenase (SDH) in mitochondria of spermatozoa was assessed by histochemical method, and spermatozoa were labeled with specific fluorescent probe of Rhodamine 123 to measure mitochondrial membrane potential (MMP) by flow cytometry.

RESULTSAfter normal spermatozoa were incubated with ROS, MMP of spermatozoa significantly decreased, and the activity of SDH almost decreased to zero. However, MLT had effect on reducing the damage of the mitochondrial function of sperm induced by ROS.

CONCLUSIONROS can damage the mitochondrial function of sperm by affecting MMP of spermatozoa and the activity of SDH. MLT can protect sperm mitochondria from the damage induced by ROS through its effective antioxidative potential.

Flow Cytometry ; Humans ; Male ; Melatonin ; pharmacology ; Membrane Potentials ; drug effects ; Mitochondria ; drug effects ; enzymology ; physiology ; Reactive Oxygen Species ; pharmacology ; Spermatozoa ; drug effects ; physiology ; Succinate Dehydrogenase ; metabolism

OBJECTIVETo observe the effect of Maixinkang Capsule (MXK) on Ca2t concentration and mitochondrial membrane potential in liver cells of ApoE(-/-) mice.

METHODSLiver cells from ApoE(-/-) mice were separated using collagenase digestive method. After the primary cells were cultured for 8 days in vitro, the concentration of 10% MXK contained rat's serum was added into the culture fluid. The Ca2+ concentration and mitochondrial membrane potential in liver cells after 48-hr culture were measured by confocal laser scanning microscopy with Flou-3 and Jc-1 as probes.

RESULTSMXK could decrease Ca2+ concentration in liver cells, which was significantly different to that in the control group (P < 0.01). Meanwhile, MXK could significantly improve mitochondrial membrane potential in liver cells (P < 0.01). There was no obvious dose-effect relationship shown in both effects of MXK.

CONCLUSIONMXK can decrease Ca2+ concentration and improve the mitochondrial membrane potential in liver cells of ApoE(-/-) mice so as to regulate the lipids and prevent the occurrence and development of hyperlipemia and atherosclerosis.

Animals ; Animals, Newborn ; Apolipoproteins E ; genetics ; Calcium Channels ; drug effects ; Hepatocytes ; physiology ; Membrane Potentials ; Mice ; Mice, Knockout ; Mitochondrial Membranes ; physiology

OBJECTIVETo investigate the effects of ropivacaine on Gamma-aminobutyric acid(GABA)-activated currents in dorsal root ganglion (DRG) neurons in rats and discuss the analgesia mechanism of ropivacaine.

METHODSBy means of using whole-cell patch-clamp technique, to investigate the modulatory effects of ropivacaine on GABA-activated currents (I(GABA)) in acutely isolated dorsal root ganglion neurons.

RESULTS(1) In 48 out of 73DRG cells (65.7%, 48/73), to perfusion ropivacaine bromide (0.1 - 1 000 micromol/L) were sensitive. Which produce in 0 to 380 pA current. (2) The majority of the neurons examined (74.5%, 73/98) were sensitive to GABA. Concentration of 1 - 1 000 micromol/L GABA could activate a concentration-dependent inward current, which manifested obvious desensitization, and the inward currents could be blocked byGABA-receptor selective antagonist of bicuculline (100 micromol/L). (3) After the neurons were treated with ropivacaine (0.1 - 1000 micromol/L) prior to the application of GABA (100 micromol/L) 30 s, GABA currents were obviously increased. Ropivacaine could make dose-response curve of the GABA up, EC50 is 23.46 micromol/L. Ropivacaine shifted the GABA dose-response curve upward and increased the maximum response to the contrast about 153%.

CONCLUSIONThe enhancement of ropivacaine to DRG neurons activation of GABA current, can lead to enhancement of pre-synaptic inhibition at the spinal cord level. This may be one of the reasons for the anesthetic effect and analgesia for ropivacaine in epidural anesthesia.

Amides ; pharmacology ; Animals ; Ganglia, Spinal ; cytology ; physiology ; Membrane Potentials ; drug effects ; Neurons ; cytology ; drug effects ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A ; physiology