• The Korean Journal of Pain
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• v.24 no.3
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• pp.131-136
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• 2011

Background: Pregabalin is an anticonvulsant and analgesic agent that interacts selectively with the voltage-sensitive-$Ca^{2+}$-channel alpha-2-delta subunit. The aim of this study was to evaluate whether the analgesic action of intrathecal (IT) pregabalin is associated with KATP channels in the rat formalin test. Methods: IT PE-10 catheters were implanted in male Sprague-Dawley rats (250.300 g) under inhalation anesthesia using enflurane. Nociceptive behavior was defined as the number of hind paw flinches during 60 min after formalin injection. Ten min before formalin injection, IT drug treatments were divided into 3 groups: normal saline (NS) $20\;{\mu}l$ (CON group); pregabalin 0.3, 1, 3 and $10\;{\mu}g$ in NS $10\;{\mu}l$ (PGB group); glibenclamide $100\;{\mu}g$ in DMSO $5\;{\mu}l$ with pregabalin 0.3, 1, 3 and $10\;{\mu}g$ in NS $5\;{\mu}l$ (GBC group). All the drugs were flushed with NS $10\;{\mu}l$. Immunohistochemistry for the $K_{ATP}$ channel was done with a different set of rats divided into naive, NS and PGB groups. Results: IT pregabalin dose-dependently decreased the flinching number only in phase 2 of formalin test. The log dose response curve of the GBC group shifted to the right with respect to that of the PGB group. Immunohistochemistry for the $K_{ATP}$ channel expression on the spinal cord dorsal horn showed no difference among the groups 1 hr after the formalin test. Conclusions: The antinociceptive effect of pregabalin in the rat formalin test was associated with the activation of the $K_{ATP}$ channel. However, pregabalin did not induce $K_{ATP}$ channel expression in the spinal cord dorsal horn.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.3
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• pp.743-748
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• 2005

This study was performed for the investigation of vasodilatory efficacy and its underlying mechanisms of Jagumhuan(JGH), a herbal remedy. JGH produced completely endothelium-dependent relaxation and relaxed phenylephrine(PE)-precontracted aorta in a concentration dependent manner. The magnitude of relaxation was greater in PE induced contraction than that of KCl, suggesting involvement of $K^+$ channel in the relaxant effect. Both glibenclamide$(10^{-5}M)$, a $K_{ATP}$ channel inhibitor and indometacin, a cyclooxygenase inhibitor, completely prevented this relaxation. The relaxation effects of JGH, involve in part the release of nitric oxide from the endothelium as pretreatment with L-NAME, an NOS inhibitor, and methylene blue, a cGMP inhibitor, attenuated the responses by 62% and 58%, respectively. In addition, nitrite was produced by JGH in human aortic smooth muscle cells and human umbilical vein endothelial cells. The relaxant effect of JGH was also inhibited by 55.41% by tetraethylammonium(TEA; 5mM), a $K_{Ca}$ channel inhibitor. In the absence of extracellular $Ca^{2+}$, pre-incubation of the aortic rings with JGH significantly reduced the contraction by PE, suggesting that the relaxant action of the JGH includes inhibition of $Ca^{2+}$ release from intracellular stores. These results indicate that in rat thoracic aorta, JGH may induce vasodilation through ATP sensitive $K^+$ channel activation by prostacyclin production. However, the relaxant effect of JGH may also mediated in part by NO pathways and $Ca^{2+}$ activated $K^+$ channel.

• Journal of Ginseng Research
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• v.23 no.4
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• pp.235-238
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• 1999

ATP-sensitive $K^+$ channels $(K_{ATP})$ are expressed in vascular smooth muscle cells, skeletal muscle cells, pancreatic ${\beta}$ cells, neurons and epithelial cells. $K_{ATP}$ contributes to regulate membrane potential to control vascular tone, to protect myocardial ischemia, and to regulate insulin secretion in pancreatic ${\beta}$ cells. We previously demonstrated that ginseng saponins and ginsenoside $Rg_3$ activated maxi $Ca^{2+}-activated\;K^+$ channel, and this might cause vasodilation. Because $K_{ATP}$ plays an important roles to regulate the resting membrane potential in vascular smooth muscle cells, we investigated whether ginsenoside $Rg_3$ produces vasodilation by activating $K_{ATP}$ We showed in this study that $K_{ATP}$ is expressed in rabbit coronary artery smooth muscle cells. $K_{ATP}$ was inwardly rectifying and was inhibited by intemal application of ATP. Micromolar minoxidil activated, but glyburide inhibited the activity of $K_{ATP}$ Ginsenoside $Rg_3$ relieved inactivaiton of whole-cell $K_{ATP}$ current without affecting the peak amplitude of $K_{ATP}$ currents presumably due to more opening of the channels.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.1
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• pp.7-12
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• 2008

OLETF (Otsuka Long-Evans Tokushima Fatty) rats are characterized by obesity-related insulin resistance, which is a phenotype of type 2 diabetes. Sulfonylurea drugs or benzoic acid derivatives as inhibitors of the ATP-sensitive potassium $(K_{ATP})$ channel are commercially available to treat diabetes. The present study compared sulfonylurea drugs (glimepiride and gliclazide) with one of benzoic acid derivatives (repaglinide) in regard to their long-term effect on ameliorating insulin sensitivity in OLETF rats. Each drug was dissolved and fed with drinking water from 29 weeks of age. On high glucose loading at 45 weeks of age, response of blood glucose recovery was the greatest in the group treated with glimepiride. On immunohistochemistry analysis for the Kir6.2 subunit of $K_{ATP}$ channels, insulin receptor ${\beta}$-subunits, and glucose transporters (GLUT) type 2 and 4 in liver, fat and skeletal muscle tissues, the sulfonylurea drugs (glimepiride and gliclazide) were more effective than repaglinide in recovery from their decreased expressions in OLETF rats. From these results, it seems to be plausible that $K_{ATP}$-channel inhibitors containing sulfonylurea moiety may be much more effective in reducing insulin resistance than those with benzoic acid moiety. In contrast to gliclazide, non-tissue selectivity of glimepiride on $K_{ATP}$ channel inhibition may further strengthen an amelioration of insulin sensitivity unless considering other side effects.

• Journal of Ginseng Research
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• v.31 no.2
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• pp.79-85
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• 2007

Compound K (CK) is a final metabolite of panaxadiol ginsenosides. Although panax ginseng is known to have anti-diabetic activity, the active ingredient is not yet fully identified. Therefore, it would be interesting to know whether and how CK has an anti-diabetic activity. First, insulin secretion-stimulating activity of CK was examined using RIN-m5F cell line and primary cultured islets. CK enhanced the insulin secretion in a concentration dependent manner. This effect, however, was almost completely abolished in the presence of diazoxide, $K^+$ channel opener, indicating that the insulin secretion-stimulating activity of CK is presumably due to blockade of ATP sensitive $K^+$ channel. In addition, effects of CK on gene expressions of hepatic enzymes (phosphoenolpyruvate carboxykinase[PEPCK], glucose-6-phos-phatase[G6Pase]) and on adipocyte differentiation in H4IIE and 3T3-Ll cells, respectively, were examined. CK suppressed the induction of PEPCK and G6Pase mRNA expressions under the dexamethasone/cAMP stimulation condition. CK also reduced the $PPAR-{\gamma}$ mRNA expression and triglyceride accumulation in a dose dependent manner as compared to the control. The present study suggests that CK deserves to examine whether it shows an anti-diabetic activity in animal and human studies.

• YAKHAK HOEJI
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• v.41 no.2
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• pp.241-246
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• 1997

The effect of potassium channel openers, SKP-450, SKP-818 and lemakalim have been compared in rat heart and aorta. In rat isolated heart, SKP-450 had a greater negative inotrop ic effect than lemakalim and KR-30818 against left ventricular developed pressure (LVDP) and double product of heart rate and LVDP (DP). In addition, SKP-450 had a greater effect than lemakalim and KR-30818 in increasing coronary flow, indicating a more potent vasodilating effect in coronary artery. Negative inotropic effect and coronary vasodilating effect of SKP-450 and SEP-818 were significantly reduced by 10 min-perfusion with $10^{-6}M$ glyburide, a selective blocker of ATP-sensitive potassium channel. In rat aorta, SKP-30450 and SKP-30818 as well as lemakalim induced powerful concentration-dependent relaxations against norepinephrinc-induced tone ($EC_{50},\;{\mu}M$ : SKP-30450, $0.107{\pm}0.009$; SKP-30818, $0.476{\pm}0.022$ ; lemakalim, $0.565{\pm}0.039$ ). These relaxant effects were significantly reduced by pretreatment with glyburide. In sununary, SKP-30450 and SKP-30818 showed greater negative inotropic and vasorelaxant effect than lemakalim in rat aorta with order of potency of SKP-30450 > SKP-30818 > lemakalim. These actions are suggested to be mediated at least in part by a mechanism which involves the opening of ATP-sensitive potassium channel.

• The Journal of Korean Physical Therapy
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• v.14 no.2
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• pp.1-15
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• 2002

Excitation-contraction coupling in skeletal muscle is process by which depolarization of the muscle fiber membrane, elicited by a nerve action potential, triggers the release of $Ca^{2+}$ from the sarcoplasmic reticulum(SR). The resulting rise in intracellular $Ca^{2+}$ concentration$([Ca^{2+}]_i)$ activates the troponin complex, thereby initiating the contraction of the muscle. The question remains as to what factors are involved in the inhibition of SR $Ca^{2+}$ release in fatigued muscle. The purpose of this study was determine whether ATP-sensitive $K^+(K_{ATP})$ channels are activated and contribute to decrease in $[Ca^{2+}]_i$ during fatigue development in the mouse skeletal muscle. To elucidate a role of $K_{ATP})$ in relation to ECC, I measured the modulation effects of $K_{ATP})$ channel blocker(glibenclamide) and opener(pinacidil) on $[Ca^{2+}]_i$ after fatiguing electrical field stimulation(FEFS). Intracellular $Ca^{2+}$ signals were recorded by conforcal laser microscopy(LSM 410) and monitored using the fluorescent $Ca^{2+}$-Sensitive indicator Fluo-3 AM. The results of this study were as followed: 1. The relative [Ca2'li after FEFS in the pre-glibenclamide-treated group was higher than the control. And relative $[Ca^{2+}]_i$ after FEFS in the pre-glibenclamide-treated group was lower than the control. 2. The relative $[Ca^{2+}]_i$ after FEFS for 3 min in the control, pre-glibenclamide-treated group and pre-pinacidil-treated group showed a similar pattern; the gradually significant decrease in $[Ca^{2+}]_i$. But, these decreasing pattern was most significant in the control. These findings suggest a tight relationship between $K_{ATP})$ and $Ca^{2+}$ in ECC during fatigue. Therefore, 1 thought that activation of $K_{ATP})$ channels may be one of mechanisms of the fatigue in skeletal muscle.

• The Korean Journal of Physiology
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• v.30 no.2
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• pp.209-218
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• 1996

Acetylcholine (ACh) activates the inwardly rectifying muscarinic $K^{+}$ channel in rat atrial cells via pertussis toxin (PTX)-sensitive G-protein ($G_k$) coupled with the muscarinic receptor (mAChR). Although this $K^{+}\;(K_{ACh})$ channel function has reported to be modulated by the phosphorylation process, a kinase and phosphatase involved in these processes are still unclear. Since either PKA or PKC was not effective on this ATP-modulation, the present study examined the possible involvement of the protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) in the function of the $K_{ACh}$ Channel. In the inside-out (I/O) patch preparation excised from the adult rat atrial cell, when activated by 10 ${\mu}M$ ACh in the pipette and 100 ${\mu}M$ GTP in the bath, the mean open time (${\tau}_{o}$) and the channel activity ($K_{ACh}$) was 1.13 ms (n=5) and 0.19 (n=6), respectively. Following the application of 1 mM ATP into the bath, ${\tau}_{o}$ increased by 34% (1.54 ms, n=5) and $K_{ACh}$ by 66% (0.28, n=6). Channel function elevated by ATP was lasted after washout of ATP. However, this ATP-induced increase in the $K_{ACh}$ channel function did not occur in pretreated cells with genistein ($50{\sim}100 {\mu}M$), a selective PTK inhibitor, but occurred in pretreated cells with equimolar daidzein, a negative control of the genistein. On the contrary, PTP which acts on tyrosine residue conversely reversed both ATP-induced increased ${\tau}_{o}$ by 32% (1.20 ms, n=3) and $K_{ACh}$ by 41% (0.15, n=3), respectively. Taken together, these results suggest that $K_{ACh}$ channel may, at least partly, be regulated by the tyrosyl phosphorylation, although it is unclear where this process exerts on the muscarinic signal transduction pathway comprising the mAChR-$G_{k}$-the $K_{ACh}$ channel.

• The Korean Journal of Physiology
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• v.28 no.1
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• pp.37-50
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• 1994

Synthetic potassium channel openers (KCOs) are agents capable of opening K-channels in excitable cells. These agents are known to have their maximal potency in the smooth muscle tissue, especially in the vascular smooth muscle. Much attention has been focused on the type of K-channel that is responsible for mediating the effects of KCOs. As the KCO-induced changes are antagonized by glibenclamide, an $K_{ATP}$ (ATP-sensitive K-channel) blocker in the pancreatic ${\beta}-cell,\;K_{ATP}$ was suggested to be the channel responsible. However, there also are many results in favor of other types of K-channel $$(maxi-K,\;small\;conductance\;K_{Ca,}\; SK_{ATP}) mediating the effects of KCOs. Effects of lemakalim, (-)enantiomer of cromakalim (BRL 34915), on the spontaneous contractions and slow waves, were investigated in the antral circular muscle of the guinea-pig stomach. Membrane currents and the effects on membrane currents and single channel activities were also measured in single smooth muscle cells and excised membrane patches by using the patch clamp method. Lemakalim induced hyperpolarization and inhibited spontaneous contractions in a dose-dependent manner. These effects were blocked by glibenclamide and low concentrations of tetraethyl ammonium (< mM). Glibenclamide blocked the effect of lemakalim on the membrane potential and slow waves. The mechanoinhibitory effect of lemakalim was blocked by pretreatment with glibenclamide. In a whole ceIl patch clamp condition, lemakalim largely increased outward K currents. These outward K currents were blocked by TEA, glibenclamide and a high concentration of intracelIular EGTA (10 mM). Volatage-gated Ca currents were not affected by lemakalim. In inside-out patch clamp experiments, lemakalim increased the opening frequency of the large conductance $Ca^{2+}-activated$ K channels $(BK_{Ca},\;Maxi-K).$ From these results, it is suggested that lemakalim induces hyperpolarization by opening K-channels which are sensitive to internal Ca and such a hyperpolarization leads to the inhibition of the spontaneous contraction.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.2
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• pp.95-100
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• 2004

Ischemic preconditioning (IPC) has been accepted as a heart protection phenomenon against ischemia and reperfusion (I/R) injury. The activation of ATP-sensitive potassium $(K_{ATP})$ channels and the release of myocardial nitric oxide (NO) induced by IPC were demonstrated as the triggers or mediators of IPC. A common action mechanism of NO is a direct or indirect increase in tissue cGMP content. Furthermore, cGMP has also been shown to contribute cardiac protective effect to reduce heart I/R-induced infarction. The present investigation tested the hypothesis that $K_{ATP}$ channels attenuate DNA strand breaks and oxidative damage in an in vitro model of I/R utilizing rat ventricular myocytes. We estimated DNA strand breaks and oxidative damage by mean of single cell gel electrophoresis with endonuclease III cutting sites (comet assay). In the I/R model, the level of DNA damage increased massively. Preconditioning with a single 5-min anoxia, diazoxide $(100\;{\mu}M)$, SNAP $(300\;{\mu}M)$ and 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate (8-pCPT-cGMP) $(100\;{\mu}M)$ followed by 15 min reoxygenation reduced DNA damage level against subsequent 30 min anoxia and 60 min reoxygenation. These protective effects were blocked by the concomitant presence of glibenclamide $(50\;{\mu}M)$, 5-hydroxydecanoate (5-HD) $(100\;{\mu}M)$ and 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate, Rp-isomer (Rp-8-pCPT-cGMP) $(100\;{\mu}M)$. These results suggest that NO-cGMP-protein kinase G (PKG) pathway contributes to cardioprotective effect of $K_{ATP}$ channels in rat ventricular myocytes.