• Molecules and Cells
• /
• 제37권11호
• /
• pp.804-811
• /
• 2014

The protease-activated receptor (PAR)-2 is highly expressed in endothelial cells and vascular smooth muscle cells. It plays a crucial role in regulating blood pressure via the modulation of peripheral vascular tone. Although several mechanisms have been suggested to explain PAR-2-induced hypotension, the precise mechanism remains to be elucidated. To investigate this possibility, we investigated the effects of PAR-2 activation on N-type $Ca^{2+}$ currents ($I_{Ca-N}$) in isolated neurons of the celiac ganglion (CG), which is involved in the sympathetic regulation of mesenteric artery vascular tone. PAR-2 agonists irreversibly diminished voltage-gated $Ca^{2+}$ currents ($I_{Ca}$), measured using the patch-clamp method, in rat CG neurons, whereas thrombin had little effect on $I_{Ca}$. This PAR-2-induced inhibition was almost completely prevented by ${\omega}$-CgTx, a potent N-type $Ca^{2+}$ channel blocker, suggesting the involvement of N-type $Ca^{2+}$ channels in PAR-2-induced inhibition. In addition, PAR-2 agonists inhibited $I_{Ca-N}$ in a voltage-independent manner in rat CG neurons. Moreover, PAR-2 agonists reduced action potential (AP) firing frequency as measured using the current-clamp method in rat CG neurons. This inhibition of AP firing induced by PAR-2 agonists was almost completely prevented by ${\omega}$-CgTx, indicating that PAR-2 activation may regulate the membrane excitability of peripheral sympathetic neurons through modulation of N-type $Ca^{2+}$ channels. In conclusion, the present findings demonstrate that the activation of PAR-2 suppresses peripheral sympathetic outflow by modulating N-type $Ca^{2+}$ channel activity, which appears to be involved in PAR-2-induced hypotension, in peripheral sympathetic nerve terminals.

• The Korean Journal of Physiology and Pharmacology
• /
• 제24권5호
• /
• pp.433-440
• /
• 2020

The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) is the first relay site for the orofacial nociceptive inputs via the thin myelinated Aδ and unmyelinated C primary afferent fibers. Borneol, one of the valuable time-honored herbal ingredients in traditional Chinese medicine, is a popular treatment for anxiety, anesthesia, and antinociception. However, to date, little is known as to how borneol acts on the SG neurons of the Vc. To close this gap, the whole-cell patch-clamp technique was applied to elucidate the antinociceptive mechanism responding for the actions of borneol on the SG neurons of the Vc in mice. In the voltage-clamp mode, holding at -60 mV, the borneol-induced non-desensitizing inward currents were not affected by tetrodotoxin, a voltage-gated Na⁺ channel blocker, 6-cyano-7-nitro-quinoxaline-2,3-dione, a non-N-methyl-ᴅ-aspartate (NMDA) glutamate receptor antagonist and DL-2-amino-5-phosphonopentanoic acid, an NMDA receptor antagonist. However, borneol-induced inward currents were partially decreased in the presence of picrotoxin, a γ-aminobutyric acid (GABA)_A receptor antagonist, or strychnine, a glycine receptor antagonist, and was almost suppressed in the presence of picrotoxin and strychnine. Though borneol did not show any effect on the glycine-induced inward currents, borneol enhanced GABA-mediated responses. Beside, borneol enhanced the GABA-induced hyperpolarization under the current-clamp mode. Altogether, we suggest that borneol contributes in part toward mediating the inhibitory GABA and glycine transmission on the SG neurons of the Vc and may serve as an herbal therapeutic for orofacial pain ailments.

• Journal of Ginseng Research
• /
• 제36권1호
• /
• pp.47-54
• /
• 2012

Korean red ginseng (KRG) has been used worldwide as a traditional medicine for the treatment of various reproductive diseases. Gonadotropin releasing hormone (GnRH) neurons are the fundamental regulators of pulsatile release of gonadotropin required for fertility. In this study, an extract of KRG (KRGE) was applied to GnRH neurons to identify the receptors activated by KRGE. The brain slice patch clamp technique in whole cell and perforated patch was used to clarify the effect of KRGE on the membrane currents and membrane potentials of GnRH neurons. Application of KRGE (3 ${\mu}g$/${\mu}L$) under whole cell patch induced remarkable inward currents (56.17${\pm}$7.45 pA, n=25) and depolarization (12.91${\pm}$3.80 mV, n=4) in GnRH neurons under high $Cl^-$ pipette solution condition. These inward currents were not only reproducible, but also concentration dependent. In addition, inward currents and depolarization induced by KRGE persisted in the presence of the voltage gated $Na^+$ channel blocker tetrodotoxin (TTX), suggesting that the responses by KRGE were postsynaptic events. Application of KRGE under the gramicidin perforated patch induced depolarization in the presence of TTX suggesting its physiological significance on GnRH response. Further, the KRGE-induced inward currents were partially blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; non-NMDA glutamate receptor antagonist, 10 ${\mu}M$) or picrotoxin (PIC; $GABA_A$ receptor antagonist, 50 ${\mu}M$), and almost blocked by PIC and CNQX mixture. Taken together, these results suggest that KRGE contains ingredients with possible GABA and non-NMDA glutamate receptor mimetic activity, and may play an important role in the endocrine function of reproductive physiology, via activation of $GABA_A$ and non-NMDA glutamate receptors in GnRH neurons.

• Journal of Ginseng Research
• /
• 제35권2호
• /
• pp.219-225
• /
• 2011

Korean red ginseng (KRG) is a valuable and important traditional medicine in East Asian countries and is currently used extensively for botanical products in the world. KRG has both stimulatory and inhibitory effects on the central nervous system (CNS) suggesting its complicated action mechanisms. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) are involved in orofacial nociceptive processing. Some studies reported that KRG has antinociceptive effects, but there are few reports of the functional studies of KRG on the SG neurons of the Vc. In this study, a whole cell patch clamp study was performed to examine the action mechanism of a KRG extract on the SG neurons of the Vc from juvenile mice. KRG induced short-lived and repeatable inward currents on all the SG neurons tested in the high chloride pipette solution. The KRG-induced inward currents were concentration dependent and were maintained in the presence of tetrodotoxin, a voltage gated $Na^+$ channel blocker. The KRG-induced inward currents were suppressed by 6-cyano-7-nitroquinoxaline-2,3-dione, a non-N-methyl-D-aspartate (NMDA) glutamate receptor antagonist and/or picrotoxin, a gamma-aminobutyric acid $(GABA)_A$ receptor antagonist. However, the inward currents were not suppressed by d,l-2-amino-5-phosphonopentanoic acid, an NMDA receptor antagonist. These results show that KRG has excitatory effects on the SG neurons of the Vc via the activation of non-NMDA glutamate receptor as well as an inhibitory effect by activation of the $GABA_A$ receptor, indicating the KRG has both stimulatory and inhibitory effects on the CNS. In addition, KRG may be a potential target for modulating orofacial pain processing.

• The Korean Journal of Physiology and Pharmacology
• /
• 제1권5호
• /
• pp.485-493
• /
• 1997

We investigated the effect of ${\alpha}-adrenergic$ and cholinergic receptor agonists on $Ca^{2+}$ current in adult rat trigeminal ganglion neurons using whole-cell patch clamp methods. The application of acetylcholine, carbachol, and oxotremorine ($50\;{\mu}M\;each$) produced a rapid and reversible reduction of the $Ca^{2+}$ current by $17{\pm}6%,\;19{\pm}3%,\;and\;18{\pm}4%$, respectively. Atropine, a muscarinic antagonist, blocked carbachol- induced $Ca^{2+}$ current inhibition to $3{\pm}1%$. Norepinephrine ($50\;{\mu}M$) reduced $Ca^{2+}$ current by $18{\pm}2%$, while clonidine ($50\;{\mu}M$), an ${\alpha}2-adrenergic$ receptor agonist, inhibited $Ca^{2+}$ current by only $4{\pm}1%$. Yohimbine, an ${\alpha}2-adrenergic$ receptor antagonist, did not block the inhibitory effect of norepinephrine on $Ca^{2+}$ current, whereas prazosin, an ${\alpha}1-adrenergic$ receptor antagonist, attenuated the inhibitory effect of norepinephrine on $Ca^{2+}$ current to $6{\pm}1%$. This pharmacology contrasts with ${\alpha}2-adrenergic$ receptor modulation of $Ca^{2+}$ channels in rat sympathetic neurons, which is sensitive to clonidine and blocked by yohimbine. Our data suggest that the modulation of voltage dependent $Ca^{2+}$ channel by norepinephrine is mediated via an α1-adrenergic receptor. Pretreatment with pertussis toxin (250 ng/ml) for 16 h greatly reduced norepinephrine- and carbachol-induced $Ca^{2+}$ current inhibition from $17{\pm}3%\;and\;18{\pm}3%\;to\;2{\pm}1%\;and\;2{\pm}1%$, respectively. These results demonstrate that norepinephrine, through an ${\alpha}1-adrenergic$ receptor, and carbachol, through a muscarinic receptor, inhibit $Ca^{2+}$ currents in adult rat trigeminal ganglion neurons via pertussis toxin sensitive GTP-binding proteins.

• Molecules and Cells
• /
• 제37권3호
• /
• pp.202-212
• /
• 2014

ClC-1 is a member of a large family of voltage-gated chloride channels, abundantly expressed in human skeletal muscle. Mutations in ClC-1 are associated with myotonia congenita (MC) and result in loss of regulation of membrane excitability in skeletal muscle. We studied the electrophysiological characteristics of six mutants found among Korean MC patients, using patch clamp methods in HEK293 cells. Here, we found that the autosomal dominant mutants S189C and P480S displayed reduced chloride conductances compared to WT. Autosomal recessive mutant M128I did not show a typical rapid deactivation of Cl- currents. While sporadic mutant G523D displayed sustained activation of $Cl^-$ currents in the whole cell traces, the other sporadic mutants, M373L and M609K, demonstrated rapid deactivations. $V_{1/2}$ of these mutants was shifted to more depolarizing potentials. In order to identify potential effects on gating processes, slow and fast gating was analyzed for each mutant. We show that slow gating of the mutants tends to be shifted toward more positive potentials in comparison to WT. Collectively, these six mutants found among Korean patients demonstrated modifications of channel gating behaviors and reduced chloride conductances that likely contribute to the physiologic changes of MC.

• The Korean Journal of Physiology and Pharmacology
• /
• 제27권4호
• /
• pp.399-406
• /
• 2023

Voltage-dependent K⁺ (Kv) channels are widely expressed on vascular smooth muscle cells and regulate vascular tone. Here, we explored the inhibitory effect of encainide, a class Ic anti-arrhythmic agent, on Kv channels of vascular smooth muscle from rabbit coronary arteries. Encainide inhibited Kv channels in a concentration-dependent manner with an IC₅₀ value of 8.91 ± 1.75 μM and Hill coefficient of 0.72 ± 0.06. The application of encainide shifted the activation curve toward a more positive potential without modifying the inactivation curve, suggesting that encainide inhibited Kv channels by altering the gating property of channel activation. The inhibition by encainide was not significantly affected by train pulses (1 and 2 Hz), indicating that the inhibition is not use (state)-dependent. The inhibitory effect of encainide was reduced by pretreatment with the Kv1.5 subtype inhibitor. However, pretreatment with the Kv2.1 subtype inhibitor did not alter the inhibitory effects of encainide on Kv currents. Based on these results, encainide inhibits vascular Kv channels in a concentration-dependent and use (state)-independent manner by altering the voltage sensor of the channels. Furthermore, Kv1.5 is the main Kv subtype involved in the effect of encainide.

• The Korean Journal of Physiology and Pharmacology
• /
• 제15권5호
• /
• pp.285-289
• /
• 2011

Shilajit, a medicine herb commonly used in Ayurveda, has been reported to contain at least 85 minerals in ionic form that act on a variety of chemical, biological, and physical stressors. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) are involved in orofacial nociceptive processing. Shilajit has been reported to be an injury and muscular pain reliever but there have been few functional studies of the effect of Shilajit on the SG neurons of the Vc. Therefore, whole cell and gramicidin-perfotrated patch clamp studies were performed to examine the action mechanism of Shilajit on the SG neurons of Vc from mouse brainstem slices. In the whole cell patch clamp mode, Shilajit induced short-lived and repeatable inward currents under the condition of a high chloride pipette solution on all the SG neurons tested. The Shilajit-induced inward currents were concentration dependent and maintained in the presence of tetrodotoxin (TTX), a voltage gated $Na^+$ channel blocker, CNQX, a non-NMDA glutamate receptor antagonist, and AP5, an NMDA receptor antagonist. The Shilajit-induced responses were partially suppressed by picrotoxin, a $GABA_A$ receptor antagonist, and totally blocked in the presence of strychnine, a glycine receptor antagonist, however not affected by mecamylamine hydrochloride (MCH), a nicotinic acetylcholine receptor antagonist. Under the potassium gluconate pipette solution at holding potential 0 mV, Shilajit induced repeatable outward current. These results show that Shilajit has inhibitory effects on the SG neurons of Vc through chloride ion channels by activation of the glycine receptor and $GABA_A$ receptor, indicating that Shilajit contains sedating ingredients for the central nervous system. These results also suggest that Shilajit may be a potential target for modulating orofacial pain processing.

• The Korean Journal of Physiology and Pharmacology
• /
• 제17권2호
• /
• pp.175-180
• /
• 2013

Resveratrol is a phytoalexin found in grapes, red wine, and berries. Resveratrol has been known to have many beneficial health effects, such as anti-cancer, neuroprotective, anti-inflammatory, and life-prolonging effects. However, relatively little is known about the effects of resveratrol on the regulation of ligand-gated ion channels. We have previously reported that resveratrol regulates subsets of homomeric ligand-gated ion channels such as those of 5-$HT_{3A}$ receptors. The ${\gamma}$-aminobutyric $acid_C$($GABA_C$) receptor is mainly expressed in retinal bipolar cells and plays an important role in visual processing. In the present study, we examined the effects of resveratrol on the channel activity of homomeric $GABA_C$ receptor expressed in Xenopus oocytes injected with cRNA encoding human $GABA_C$ ${\rho}$ subunits. Our data show that the application of GABA elicits an inward peak current ($I_{GABA}$) in oocytes that express the $GABA_C$ receptor. Resveratrol treatment had no effect on oocytes injected with $H_2O$ or with $GABA_C$ receptor cRNA. Co-treatment with resveratrol and GABA inhibited $I_{GABA}$ in oocytes with $GABA_C$ receptors. The inhibition of $I_{GABA}$ by resveratrol was in a reversible and concentration-dependent manner. The $IC_{50}$ of resveratrol was $28.9{\pm}2.8{\mu}M$ in oocytes expressing $GABA_C$ receptor. The inhibition of $I_{GABA}$ by resveratrol was in voltage-independent and non-competitive manner. These results indicate that resveratrol might regulate $GABA_C$ receptor expression and that this regulation might be one of the pharmacological actions of resveratrol on the nervous system.

• The Korean Journal of Physiology and Pharmacology
• /
• 제24권1호
• /
• pp.111-119
• /
• 2020

In vascular smooth muscle, K⁺ channels, such as voltage-gated K⁺ channels (Kv), inward-rectifier K⁺ channels (Kir), and big-conductance Ca²⁺-activated K⁺ channels (BK_Ca), establish a hyperpolarized membrane potential and counterbalance the depolarizing vasoactive stimuli. Additionally, Kir mediates endothelium-dependent hyperpolarization and the active hyperemia response in various vessels, including the coronary artery. Pulmonary arterial hypertension (PAH) induces right ventricular hypertrophy (RVH), thereby elevating the risk of ischemia and right heart failure. Here, using the whole-cell patch-clamp technique, we compared Kv and Kir current densities (I_Kv and I_Kir) in the left (LCSMCs), right (RCSMCs), and septal branches of coronary smooth muscle cells (SCSMCs) from control and monocrotaline (MCT)-induced PAH rats exhibiting RVH. In control rats, (1) I_Kv was larger in RCSMCs than that in SCSMCs and LCSMCs, (2) I_Kv inactivation occurred at more negative voltages in SCSMCs than those in RCSMCs and LCSMCs, (3) I_Kir was smaller in SCSMCs than that in RCSMCs and LCSMCs, and (4) I_BKCa did not differ between branches. Moreover, in PAH rats, I_Kir and I_Kv decreased in SCSMCs, but not in RCSMCs or LCSMCs, and I_BKCa did not change in any of the branches. These results demonstrated that SCSMC-specific decreases in I_Kv and I_Kir occur in an MCT-induced PAH model, thereby offering insights into the potential pathophysiological implications of coronary blood flow regulation in right heart disease. Furthermore, the relatively smaller I_Kir in SCSMCs suggested a less effective vasodilatory response in the septal region to the moderate increase in extracellular K⁺ concentration under increased activity of the myocardium.