• 고려인삼학회:학술대회논문집
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• 고려인삼학회 2005년도 창립30주년기념 추계 학술대회 및 정기총회
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• pp.32-40
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• 2005

The last two decades have shown a marked expansion in publications of diverse effects of Panax ginseng. Ginsenosides, as active ingredients of Panax ginseng, are saponins found in only ginseng. Recently, a line of evidences shows that ginsenosides regulate various types of ion channel activity such as Ca$^{2+}$, K$^+$, Na$^+$, Cl$^-$, or ligand gated ion channels (i.e. 5-HT$_3$, nicotinic acetylcholine, or NMDA receptor) in neuronal, non-neuronal cells, and heterologously expressed cells. Ginsenosides inhibit voltage-dependent Ca$^{2+}$, K$^+$, and Na$^+$ channels, whereas ginsenosides activate Ca$^{2+}$-activated Cl$^-$ and Ca$^{2+}$-activated K$^+$ channels. Ginsenosides also inhibit excitatory ligand-gated ion channels such as 5-HT$_3$. nicotinic acetylcholine, and NMDA receptors. This presentation will introduce recent findings on the ginsenoside-induced differential regulations of ion channel activities as a ligand as other drugs do.

• The Korean Journal of Physiology and Pharmacology
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• 제21권2호
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• pp.215-223
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• 2017

The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent $K^+$ and $Ca^{2+}$ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent $K^+$currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent $K^+$ currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker $Cs^+$ (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent $Ca^{2+}$ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

• The Korean Journal of Physiology and Pharmacology
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• 제21권2호
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• pp.259-265
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• 2017

Excessive influx and the subsequent rapid cytosolic elevation of $Ca^{2+}$ in neurons is the major cause to induce hyperexcitability and irreversible cell damage although it is an essential ion for cellular signalings. Therefore, most neurons exhibit several cellular mechanisms to homeostatically regulate cytosolic $Ca^{2+}$ level in normal as well as pathological conditions. Delayed rectifier $K^+$ channels ($I_{DR}$ channels) play a role to suppress membrane excitability by inducing $K^+$ outflow in various conditions, indicating their potential role in preventing pathogenic conditions and cell damage under $Ca^{2+}$-mediated excitotoxic conditions. In the present study, we electrophysiologically evaluated the response of $I_{DR}$ channels to hyperexcitable conditions induced by high $Ca^{2+}$ pretreatment (3.6 mM, for 24 hours) in cultured hippocampal neurons. In results, high $Ca^{2+}$-treatment significantly increased the amplitude of $I_{DR}$ without changes of gating kinetics. Nimodipine but not APV blocked $Ca^{2+}$-induced $I_{DR}$ enhancement, confirming that the change of $I_{DR}$ might be targeted by $Ca^{2+}$ influx through voltage-dependent $Ca^{2+}$ channels (VDCCs) rather than NMDA receptors (NMDARs). The VDCC-mediated $I_{DR}$ enhancement was not affected by either $Ca^{2+}$-induced $Ca^{2+}$ release (CICR) or small conductance $Ca^{2+}$-activated $K^+$ channels (SK channels). Furthermore, PP2 but not H89 completely abolished $I_{DR}$ enhancement under high $Ca^{2+}$ condition, indicating that the activation of Src family tyrosine kinases (SFKs) is required for $Ca^{2+}$-mediated $I_{DR}$ enhancement. Thus, SFKs may be sensitive to excessive $Ca^{2+}$ influx through VDCCs and enhance $I_{DR}$ to activate a neuroprotective mechanism against $Ca^{2+}$-mediated hyperexcitability in neurons.

• The Korean Journal of Physiology and Pharmacology
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• 제13권6호
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• pp.461-467
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• 2009

The auditory cortex (A1) encodes the acquired significance of sound for the perception and interpretation of sound. Nitric oxide (NO) is a gas molecule with free radical properties that functions as a transmitter molecule and can alter neural activity without direct synaptic connections. We used whole-cell recordings under voltage clamp to investigate the effect of NO on spontaneous GABAergic synaptic transmission in mechanically isolated rat auditory cortical neurons preserving functional presynaptic nerve terminals. GABAergic spontaneous inhibitory postsynaptic currents (sIPSCs) in the A1 were completely blocked by bicuculline. The NO donor, S-nitroso-N-acetylpenicillamine (SNAP), reduced the GABAergic sIPSC frequency without affecting the mean current amplitude. The SNAP-induced inhibition of sIPSC frequency was mimicked by 8-bromoguanosine cyclic 3',5'-monophosphate, a membrane permeable cyclic-GMP analogue, and blocked by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a specific NO scavenger. Blockade of presynaptic $K^+$ channels by 4-aminopyridine, a $K^+$ channel blocker, increased the frequencies of GABAergic sIPSCs, but did not affect the inhibitory effects of SNAP. However, blocking of presynaptic $Ca^{2+}$ channels by $Cd^{2+}$, a general voltage-dependent $Ca^{2+}$ channel blocker, decreased the frequencies of GABAergic sIPSCs, and blocked SNAP-induced reduction of sIPSC frequency. These findings suggest that NO inhibits spontaneous GABA release by activation of cGMP-dependent signaling and inhibition of presynaptic $Ca^{2+}$ channels in the presynaptic nerve terminals of A1 neurons.

• The Korean Journal of Physiology and Pharmacology
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• 제20권1호
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• pp.119-127
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• 2016

Dihydropyridine (DHP) calcium channel blockers (CCBs) have been widely used to treat of several cardiovascular diseases. An excessive shortening of action potential duration (APD) due to the reduction of $Ca^{2+}$ channel current ($I_{Ca}$) might increase the risk of arrhythmia. In this study we investigated the electrophysiological effects of nicardipine (NIC), isradipine (ISR), and amlodipine (AML) on the cardiac APD in rabbit Purkinje fibers, voltage-gated $K^+$ channel currents ($I_{Kr}$, $I_{Ks}$) and voltage-gated $Na^+$ channel current ($I_{Na}$). The concentration-dependent inhibition of $Ca^{2+}$ channel currents ($I_{Ca}$) was examined in rat cardiomyocytes; these CCBs have similar potency on $I_{Ca}$ channel blocking with $IC_{50}$ (the half-maximum inhibiting concentration) values of 0.142, 0.229, and 0.227 nM on NIC, ISR, and AML, respectively. However, ISR shortened both $APD_{50}$ and $APD_{90}$ already at $1{\mu}M$ whereas NIC and AML shortened $APD_{50}$ but not $APD_{90}$ up to $30{\mu}M$. According to ion channel studies, NIC and AML concentration-dependently inhibited $I_{Kr}$ and $I_{Ks}$ while ISR had only partial inhibitory effects (<50% at $30{\mu}M$). Inhibition of $I_{Na}$ was similarly observed in the three CCBs. Since the $I_{Kr}$ and $I_{Ks}$ mainly contribute to cardiac repolarization, their inhibition by NIC and AML could compensate for the AP shortening effects due to the block of $I_{Ca}$.

• Asian-Australasian Journal of Animal Sciences
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• 제15권7호
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• pp.949-956
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• 2002

There are several physiological and pharmacological evidences indicating that opening of voltage dependent $Ca^{2+}$ channels play a critical role in induction of acrosome reaction in mammalian sperm. We determined the intracellular free $Ca^{2+}$ concentration in ejaculated goat sperm using a fluorescent, $Ca^{2+}$-specific probe, Fura2/AM, after the suspension of sperm in KRB medium, capable of sustaining capacitation and the acrosome reaction. We used nifedipine, D-600 and diltiazem, the $Ca^{2+}$ channel antagonists belonging to the classes of dihydropyridines, phenylalkylamines and benzothiazepines, to investigate the possibility that L-type voltage gated $Ca^{2+}$ channels play a role in the progesterone-stimulated exocytotic response. Progesterone promoted a rise in intracellular $Ca^{2+}$ in goat sperm and addition of nifedipine (100 nM) just prior to progesterone induction, significantly inhibited both intracellular $Ca^{2+}$ rise and exocytosis suggesting that $Ca^{2+}$ channels are involved in the process. However, the intracellular $Ca^{2+}$ increase during the process of capacitation was not affected with the addition of nifedipine suggesting a role of focal channel for $Ca^{2+}$ during capacitation. Studies using monensin and nigericin, two monovalent cation ionophores showed that an influx of $Na^+$ also may play a role in the opening of $Ca^{2+}$ channels. These results strongly suggests that the entry of $Ca^{2+}$ channels with characteristics similar to those of L-type, voltage-sensitive $Ca^{2+}$ channels found in cardiac and skeletal muscle, is a crucial step in the sequence of events leading to progesterone induced acrosome reaction in goat sperm.

• The Korean Journal of Physiology and Pharmacology
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• 제13권3호
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• pp.241-249
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• 2009

Although extracellular $Ca^{2+}$ entry through the voltage-dependent $Ca^{2+}$ channels plays an important role in the spontaneous phasic contractions of the pregnant rat myometrium, the role of the T-type $Ca^{2+}$ channels has yet to be fully identified. The aim of this study was to investigate the role of the T-type $Ca^{2+}$ channel in the spontaneous phasic contractions of the rat myometrium. Spontaneous phasic contractions and $[Ca^{2+}]_i$ were measured simultaneously in the longitudinal strips of female Sprague-Dawley rats late in their pregnancy (on day 18 ${\sim}$ 20 of gestation: term=22 days). The expression of T-type $Ca^{2+}$ channel mRNAs or protein levels was measured. Cumulative addition of low concentrations (< 1 ${\mu}M$) of nifedipine, a L-type $Ca^{2+}$ channel blocker, produced a decrease in the amplitude of the spontaneous $Ca^{2+}$ transients and contractions with no significant change in frequency. The mRNAs and proteins encoding two subunits (${\alpha}$ 1G, ${\alpha}$ 1H) of the T-type $Ca^{2+}$ channels were expressed in longitudinal muscle layer of rat myometrium. Cumulative addition of mibefradil, NNC 55-0396 or nickel induced a concentration-dependent inhibition of the amplitude and frequency of the spontaneous $Ca^{2+}$ transients and contractions. Mibefradil, NNC 55-0396 or nickel also attenuated the slope of rising phase of spontaneous $Ca^{2+}$ transients consistent with the reduction of the frequency. It is concluded that T-type $Ca^{2+}$ channels are expressed in the pregnant rat myometrium and may play a key role for the regulation of the frequency of spontaneous phasic contractions.

• Archives of Pharmacal Research
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• 제21권3호
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• pp.315-319
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• 1998

Gastric smooth muscle of cats was used to investigate the involvement of protein kinase in vanadate-induced contraction. Vanadate caused a contraction of cat gastric smooth muscle in a dose-dependent manner. Vanadate-induced contraction was totally inhibited by 2 mM EGTA and 1.5 mM $LACI_3$ and significantly inhibited by $10\mu$M verapamil and $1\mu$M nifedipine, suggesting that vanadate-induced contraction is dependent on the extracellular $Ca^{2+}$ concentration, and the influx of extracellular $Ca^{2+}$ was mediated through voltage-dependent $Ca^{2+}$ channel. Both protein kinase C inhibitor and tyrosine kinase inhibitor significantly inhibited the vanadate-induced contraction and the combined inhibitory effect of two protein kinase inhibitors was greater than that of each one. But calmodulin antagonists did not have any influence on the vanadate-induced contraction. On the other hand, both forskolin ($1\mu$M) and sodium nitroprusside ($1\mu$M) significantly inhibited vanadate-induced contraction. Therefore, these results suggest that both protein kinase C and tyrosino kinase are involved in the vanadate-induced contraction which required the influx of extracellular $Ca^{2+}$ in cat gastric smooth muscle, and that the contractile mechanism of vanadate may be different from that of agonist binding to its specific receptor.

• Molecules and Cells
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• 제21권1호
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• pp.52-62
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• 2006

In previous reports we demonstrated that ginsenosides, active ingredients of Panax ginseng, affect some subsets of voltage-dependent $Ca^{2+}$ channels in neuronal cells expressed in Xenopus laevis oocytes. However, the major component(s) of ginseng that affect cloned $Ca^{2+}$ channel subtypes such as ${\alpha}_{1C}$(L)-, ${\alpha}_{1B}$(N)-, ${\alpha}_{1A}$(P/Q)-, ${\alpha}_{1E}$(R)- and ${\alpha}_{1G}$(T) have not been identified. Here, we used the two-microelectrode voltage clamp technique to characterize the effects of ginsenosides and ginsenoside metabolites on $Ba^{2+}$ currents ($I_{Ba}$) in Xenopus oocytes expressing five different $Ca^{2+}$ channel subtypes. Exposure to ginseng total saponins (GTS) induced voltage-dependent, dose-dependent and reversible inhibition of the five channel subtypes, with particularly strong inhibition of the ${\alpha}_{1G}$-type. Of the various ginsenosides, $Rb_1$, Rc, Re, Rf, $Rg_1$, $Rg_3$, and $Rh_2$, ginsenoside $Rg_3$ also inhibited all five channel subtypes and ginsenoside $Rh_2$ had most effect on the ${\alpha}_{1C}$- and ${\alpha}_{1E}$-type $Ca^{2+}$ channels. Compound K (CK), a protopanaxadiol ginsenoside metabolite, strongly inhibited only the ${\alpha}_{1G}$-type of $Ca^{2+}$ channel, whereas M4, a protopanaxatriol ginsenoside metabolite, had almost no effect on any of the channels. $Rg_3$, $Rh_2$, and CK shifted the steady-state activation curves but not the inactivation curves in the depolarizing direction in the ${\alpha}_{1B}$- and ${\alpha}_{1A}$-types. These results reveal that $Rg_3$, $Rh_2$ and CK are the major inhibitors of $Ca^{2+}$ channels in Panax ginseng, and that they show some $Ca^{2+}$ channel selectivity.

• 한국발생생물학회지:발생과생식
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• 제15권1호
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• pp.31-39
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• 2011

Change in intracellular $Ca^{2+}$-concentration ($[Ca^{2+}]_i$) is an essential event for egg activation and further development. $Ca^{2+}$ ion is originated from intracellular $Ca^{2+}$-store via inositol 1,4,5-triphosphate receptor and/or $Ca^{2+}$ influx via $Ca^{2+}$ channel. This study was performed to investigate whether changes in $Ca^{2+}$/calmodulin dependent protein kinase II (CaM KII) activity affect $Ca^{2+}$ influx during artificial egg activation with ethanol using $Ca^{2+}$ monitoring system and whole-cell patch clamp technique. Under $Ca^{2+}$ ion-omitted condition, $Ca^{2+}$-oscillation was stopped within 30 min post microinjection of porcine sperm factor, and ethanol-induced $Ca^{2+}$ increase was reduced. To investigate the role of CaM KII known as an integrator of $Ca^{2+}$- oscillation during mammalian egg fertilization, CaM KII activity was tested with a specific inhibitor KN-93. In the eggs treated with KN-93, ethanol failed to induce egg activation. In addition, KN-93 inhibited inward $Ca^{2+}$ current ($I_{Ca}$) in a time-dependent manner in whole-cell configuration. Immunostaining data showed that the voltage-dependent $Ca^{2+}$ channels were distributed along the plasma membrane of mouse egg and 2-cell embryo. From these results, we suggest that $Ca^{2+}$ influx during fertilization might be controlled by CaM KII activity.