• Journal of Ginseng Research
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• v.44 no.3
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• pp.490-495
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• 2020

Background: Ginsenoside Rk1, a saponin component isolated from heat-processed Panax ginseng Meyer, has been implicated in the regulation of antitumor and anti-inflammatory activities. Although our previous studies have demonstrated that ginsenoside Rg3 significantly attenuated the activation of NMDA receptors (NMDARs) in hippocampal neurons, the effects of ginsenosides Rg5 and Rk1, which are derived from heat-mediated dehydration of ginsenoside Rg3, on neuronal NMDARs have not yet been elucidated. Methods: We examined the regulation of NMDARs by ginsenosides Rg5 and Rk1 in cultured rat hippocampal neurons using fura-2-based calcium imaging and whole-cell patch-clamp recordings. Results: The results from our investigation showed that ginsenosides Rg3 and Rg5 inhibited NMDARs with similar potencies. However, ginsenoside Rk1 inhibited NMDARs most effectively among the five compounds (Rg3, Rg5, Rk1, Rg5/Rk1 mixture, and protopanaxadiol) tested in cultured hippocampal neurons. Its inhibition is independent of the NMDA- and glycine-binding sites, and its action seems to involve in an interaction with the polyamine-binding site of the NMDAR channel complex. Conclusion: Taken together, our results suggest that ginsenoside Rk1 might be a novel component contributable to the development of ginseng-based therapeutic treatments for neurodegenerative diseases.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.2
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• pp.177-181
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• 2015

The subfornical organ (SFO) is one of circumventricular organs characterized by the lack of a normal blood brain barrier. The SFO neurons are exposed to circulating glutamate ($60{\sim}100{\mu}M$), which may cause excitotoxicity in the central nervous system. However, it remains unclear how SFO neurons are protected from excitotoxicity caused by circulating glutamate. In this study, we compared the glutamate-induced whole cell currents in SFO neurons to those in hippocampal CA1 neurons using the patch clamp technique in brain slice. Glutamate ($100{\mu}M$) induced an inward current in both SFO and hippocampal CA1 neurons. The density of glutamate-induced current in SFO neurons was significantly smaller than that in hippocampal CA1 neurons (0.55 vs. 2.07 pA/pF, p<0.05). To further identify the subtype of the glutamate receptors involved, the whole cell currents induced by selective agonists were then compared. The current densities induced by AMPA (0.45 pA/pF) and kainate (0.83 pA/pF), non-NMDA glutamate receptor agonists in SFO neurons were also smaller than those in hippocampal CA1 neurons (2.44 pA/pF for AMPA, p<0.05; 2.34 pA/pF for kainate, p< 0.05). However, the current density by NMDA in SFO neurons was not significantly different from that of hippocampal CA1 neurons (1.58 vs. 1.47 pA/pF, p>0.05). These results demonstrate that glutamate-mediated action through non-NMDA glutamate receptors in SFO neurons is smaller than that of hippocampal CA1 neurons, suggesting a possible protection mechanism from excitotoxicity by circulating glutamate in SFO neurons.

• Journal of Chest Surgery
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• v.25 no.4
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• pp.364-382
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• 1992

In order to investigate the effect of intracellular cyclic GMP on the calcium channel, whole cell patch clamp technique with internal perfusion method was used in the single ventricular myocytes of the rabbit. Cyclic GMP, cGMP analogues, cAMP, isopernaline and forskolin were perfused into cells and their effects on the calcium current were analysed by applying depolarizing step pulse of 10 mV in amplitude for 200 msec from holding potential of -40 mV. Calcium currents usually activated from -30 mV and then reached a peak at +10 mV. Amplitude of the calcium current was standardized with membrane capacitance, 50 pF. Peak amplitude at +10 mV in control was -0.15 nA/50pF. When 100 mM cAMP was applied from the pipette, peak amplitude of calcium current increased to -0.32 nA and addition of 1 mM isoprenaline further increased its amplitude. In the presence of cGMP it alone also produced an increase of the calcium current to -0.52 nA/50pF and addition of isoprenaline or forskolin increased its magnitude to -[0.55~0.95] nA/50pF. Simultaneous application of cGMP and cAMP increased the calcium current to -0.67 nA/50pF. Among the cGMP analogues, 8-Br-cGMP was the most potent stimulant for the calcium current activation. From the above results it could be concluded tlat cGMP increases the calcium current not through cAMP dependent protein kinase nor cAMP dependent phosphodiesterase pathway, but through independent phosphorylation pathway, possibly cGMP dependent protein kinase pathway.

• The Korean Journal of Physiology
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• v.26 no.1
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• pp.15-25
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• 1992

In order to elucidate the properties of the background current whole cell patch clamp studies were performed in rabbit ventricular cells. Ramp pulses of ${\pm}80\;mV$ from holding potential of 40 mV(or 20 mV) at the speed of 0.8 V/sec were given every 30 sec(or 10 sec) and current-voltage diagrams(I-V curve) were obtained. For the activation of the background current isoprenaline, adenosine 3',5'-cyclic monophosphate(dBcAMP), guanosine 3',5'-cyclic monophosphate(cGMP), and $N^6$-2'-o-dibutyryladenosine 3',5'-cyclic monophosphate(dBcAMP) were applied after all known current systems were blocked with 2mM Ba, 1 mM Cd ,5 mM Ni, 10 ${\mu}M$ diltiazem, 10 ${\mu}m$ ouabain, and 20 mM tetraethylammonium(TEA). The conductance of background current in control was $0.65{\pm}0.69$ nS at 0 mV, its I-V curves was almost linear and reversed near 50 mV. When there was no taurine in pipette solution, isoprenaline hardly activated the background current but when taurine existed in pipette solution, isoprenaline activated the larger background current. Cyclic AMP or cyclic GMP alone had little effect on the activation of the background current, while cGMP potentiated cGMP effect. When the background current was activated with cGMP and cAMP, isoprenaline could not further increased the background current. The background current activated by isoprenaline depended on extracellular $Cl^-$ concentration and its reversal potential was shifted according to chloride equilibrium potential. The change of extracellular $Na+$ concentration had little effect on reversal potential of the background current activated by isoprenaline.

• Korean Journal of Veterinary Research
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• v.34 no.1
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• pp.37-47
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• 1994

The effects of the novel compound GS-386 on the calcium current were investigated in rabbit atrial myocytes. The calcium current was recorded during various depolarizations of 200 ms duration from a holding potential of -40 mV using the whole cell patch clamp technique. The calcium current was activated from -30 mV, reached maximum amplitude at +10 mV and almost disappeared at +50 mV. Superfusion of GS-386 led to a reduction of the calcium current amplitude dose-dependently and $ED_{50}$ was $2.5{\times}10^{-7}M$. But the dependence of the calcium current on the membrane potential was not altered by GS-386. The inactivation of the calcium currents showed single exponential curves in both before and after application of GS-386. The inactivation time constants before and after application of GS-386 were almost the same(35 ms and 32.5 ms). The steady-state inactivation curve of the calcium current was not shifted by GS-386. The calcium currents both before and after application of GS-386 recovered completely in 1 sec and the recovery time constants were about 200 ms in both cases. From the above results it is concluded that the novel compound GS-386 has calcium antagonistic property decreasing the calcium current.

• The Korean Journal of Physiology
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• v.28 no.2
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• pp.143-150
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• 1994

The whole-cell mode of the patch clamp technique was used to study $Ca^{2+}-activated\;Cl^-\;current$ $(I_{Cl_{Ca}})$ in gastric antral myocytes. Extracellular application of caffeine evoked $Ca^{2+}-activated\;current$. In order to isolate the chloride current from background current, all known systems were blocked with specific blockers. The current-voltage relationship of caffeine-induced current showed outward rectification and it reversed at around $E_{Cl^-}$. The shift of reversal potential upon the alteration of external and internal chloride concentrations was well fitted with results which were calculated by the Nernst equation. Extracellular addition of N-phenylanthranilic acid and niflumic acid which are known anion channel blockers abolished the caffeine induced current. Intracellular application of a high concentration of EGTA also abolished this current. Application of c-AMP, c-GMP, heparin, or $AIF^-_4$ made no remarkable changes to this current. Sodium replacement with the impermeable cation N-methylglucamine or with $Cd^{2+}$ rarely affected this current. From the above results it is suggested that the caffeine induced current was a $Cl^-$ current and it was activated by intracellular $Ca^{2+}$.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.4
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• pp.301-309
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• 2000

The purpose of our investigation was to examine the effects of prostaglandin $F_{2{\alpha}}\;(PGF_{2{\alpha}})$ on membrane potentials, $Ca^{2+}-activated\;K^+\;(K_{Ca})$ channels, and delayed rectifier $K^+(K_V)$ channels using the patch-clamp technique in single rabbit middle cerebral arterial smooth muscle cells. $PGF_{2{\alpha}}$ significantly hyperpolarized membrane potentials and increased outward whole-cell K currents. $PGF_{2{\alpha}}$ increased open-state probability of $K_{Ca}$ channels without the change of the open and closed kinetics. $PGF_{2{\alpha}}$ increased the amplitudes of $K_V$ currents with a leftward shift of activation and inactivation curves and a decrease of activation time constant. Our results suggest that the activation of $K_{Ca}$ and $K_V$ channels, at least in part, may lead to attenuate or counteract vasoconstriction by $PGF_{2{\alpha}}$ in middle cerebral artery.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.5
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• pp.461-469
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• 1999

Glutamate and ${\gamma}-aminobutyric$ acid (GABA) are major excitatory and inhibitory neurotransmitters in the vertebrate retina, respectively. Using the whole-cell patch clamp technique and a rapid solution changer, glutamate and GABA receptors have been extensively investigated in carp retina. Glutamate receptors on both horizontal and amacrine cells may be an AMPA preferring subtype, which predominantly consists of flop splice variants. $GABA_A$ and $GABA_C$ receptors coexist in bipolar cells and they both show significant desensitization. Kinetics analysis demonstrated that activation, deactivation and desensitization of the $GABA_C$ receptor-mediated response of these cells are overall slower than those of the $GABA_A$ response. Endogenous modulator $Zn^{2+}$ in the retina was found to differentially modulate the kinetic characteristics of the $GABA_C$ and $GABA_A$ responses.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.1
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• pp.9-14
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• 2000

$K^+$ currents play multiple roles in the excitability of dorsal root ganglion (DRG) neurons. Influences on these currents change the shape of the action potential, its firing threshold and the resting membrane potential. In this study, whole cell configuration of patch clamp technique had been applied to record the blocking effect of capsaicin, a lipophilic alkaloid, on the delayed rectifier $K^+$ current in cultured small diameter DRG neurons of adult rat. Capsaicin reduced the amplitude of $K^+$ current in dose dependent manner, and the concentration-dependence curve was well described by the Hill equation with $K_D$ value of $19.1{\mu}M.$ The blocking effect of capsaicin was reversible. Capsaicin $(10 {\mu}M)$ shifted the steady-state inactivation curve in the hyperpolarizing direction by about 15 mV and increased the rate of inactivation. The voltage dependence of activation was not affected by capsaicin. These multiple effects of capsaicin may suggest that capsaicin bind to the region of $K^+$ channel, participating in inactivation process.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.6
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• pp.649-660
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• 2018

Migraine is a neurological disorder characterized by recurrent and disabling severe headaches. Although several anticonvulsant drugs that block voltagedependent $Na^+$ channels are widely used for migraine, far less is known about the therapeutic actions of carbamazepine on migraine. In the present study, therefore, we characterized the effects of carbamazepine on tetrodotoxin-resistant (TTX-R) $Na^+$ channels in acutely isolated rat dural afferent neurons, which were identified by the fluorescent dye DiI. The TTX-R $Na^+$ currents were measured in medium-sized DiIpositive neurons using the whole-cell patch clamp technique in the voltage-clamp mode. While carbamazepine had little effect on the peak amplitude of transient $Na^+$ currents, it strongly inhibited steady-state currents of transient as well as persistent $Na^+$ currents in a concentration-dependent manner. Carbamazepine had only minor effects on the voltage-activation relationship, the voltage-inactivation relationship, and the use-dependent inhibition of TTX-R $Na^+$ channels. However, carbamazepine changed the inactivation kinetics of TTX-R $Na^+$ channels, significantly accelerating the development of inactivation and delaying the recovery from inactivation. In the current-clamp mode, carbamazepine decreased the number of action potentials without changing the action potential threshold. Given that the sensitization of dural afferent neurons by inflammatory mediators triggers acute migraine headaches and that inflammatory mediators potentiate TTX-R $Na^+$ currents, the present results suggest that carbamazepine may be useful for the treatment of migraine headaches.