• The Korean Journal of Physiology and Pharmacology
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• v.12 no.1
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• pp.13-23
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• 2008

The aim of the present study was designed to establish comparatively the inhibitory effects of $D_1$-like and $D_2$-like dopaminergic receptor agonists, SKF81297 and R(-)-TNPA on the release of catecholamines (CA) evoked by cholinergic stimulation and membrane depolarization from the isolated perfused model of the rat adrenal medulla. SKF81297 $(30{\mu}M)$ and R-(-)-TNPA $(30{\mu}M)$ perfused into an adrenal vein for 60 min, produced great inhibition in the CA secretory responses evoked by ACh $(5.32{\times}10^{-3}\;M)$, DMPP $(10^{-4}\;M)$, McN-A-343 $(10^{-4}\;M)$, high $K^+$ $(5.6{\times}10^{-2}\;M)$, Bay-K-8644 $(10{\mu}M)$, and cyclopiazonic acid $(10{\mu}M)$, respectively. For the release of CA evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid, the following rank order of inhibitory potency was obtained: SKF81297>R-(-)-TNPA. However, R(+)-SCH23390, a selectve $D_1$-like dopaminergic receptor antagonist, and S(-)-raclopride, a selectve $D_2$-like dopaminergic receptor antagonist, enhanced the CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid only for $0{\sim}4$ min. The rank order for the enhancement of CA release evoked by high $K^+$, McN-A-343 and cyclopiazonic acid was R(+)-SCH23390>S(-)-raclopride. Also, the rank order for ACh, DMPP and Bay-K-8644 was S(-)-raclopride > R(+)-SCH23390. Taken together, these results demonstrate that both SKF81297 and R-(-)-TNPA inhibit the CA release evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors and the membrane depolarization from the isolated perfused rat adrenal gland without affecting the basal release, respectively, but both R(+)-SCH23390 and S(-)-raclopride facilitate the CA release evoked by them. It seems likely that the inhibitory effects of SKF81297 and R-(-)-TNPA are mediated by the activation of $D_1$-like and $D_2$-like dopaminergic receptors located on the rat adrenomedullary chromaffin cells, respectively, whereas the facilitatory effects of R(+)-SCH23390 and S(-)-raclopride are mediated by the blockade of $D_1$-like and $D_2$-like dopaminergic receptors, respectively: this action is possibly associated with extra- and intracellular calcium mobilization. Based on these results, it is thought that the presence of dopaminergic $D_1$ receptors may play an important role in regulation of the rat adrenomedullary CA secretion, in addition to well-known dopaminergic $D_2$ receptors.

• Journal of Embryo Transfer
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• v.20 no.3
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• pp.191-200
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• 2005

Many studies have shown that the development of mouse early 2-cell embryos in vitro is related with the intracellular $Ca^{2+}$ changes. In ICR strain mouse, the development of embryos arrests at early 2-cell stage, but the arrested early 2-cell embryos can be rescued by the addition of $Ca^{2+}$-related materials. Acetylcholine (ACh) increases intracellular $Ca^{2+}$ concentration ([$Ca^{2+}$]i) via the mAChR-PLC-IP3 pathway in mouse oocytes. We examined whether ACh rescues 2-cell block in mouse. In early 2-cell embryos, ACh increased [$Ca^{2+}$]i in a dose-dependent manner (p<0.001), and had an effect on rescue of 2-cell block and embryonic development. To identify the signal pathway involved in ACh-induced rescue of 2-cell block, we first applied an agonist of ACh receptor (AChR). Like ACh, carbachol increased intracellular $Ca^{2+}$ concentration ([$Ca^{2+}$]i) and atropine, an antagonist of ACh receptor, blocked the ACh-induced $Ca^{2+}$ increase. In $Ca^{2+}$-free medium, ACh also increased [$Ca^{2+}$]i, indicating that $Ca^{2+}$ increased by ACh is mainly released from the intracellular $Ca^{2+}$ store. The ACh-induced $Ca^{2+}$ increase was blocked by PLC inhibitor (U73122), ryanodine receptor (RyR) antagonist (dantrolene), and CaM KII inhibitor (KN-93), but not by IP3R antagonists (xestospongin C). These results show that ACh increases intracellular $Ca^{2+}$ concentration via mAChR/PLC/RyR, and this contributes to the rescue of 2-cell block.

• Clinical and Experimental Reproductive Medicine
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• v.25 no.3
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• pp.269-275
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• 1998

It has been reported that the $Ca^{2+}$-ATPase and the $Ca^{2+}-Na^+$ exchanger play an important role for the regulation of intracellular $Ca^{2+}$ in somatic cells, the $Ca^{2+}$-ATPase located in the plasma membrane helps the $Ca^{2+}$ concentration in maintain low $[Ca^{2+}]_i$. Roldan & Fleming reported that the spermatozoan $Ca^{2+}$-ATPase plays an important role in the capacitation and acrosome reaction. We used to assess $Ca^{2+}$ changes by chlortetracycline (CTC) patterns in the capacitation and acrosome reaction of human and hamster spermatozoa. In the present study applying quercetin which has been known as an ATPase antagonist, the enzymatic effect of $Ca^{2+}$-ATPase on capacitation and acrosome reaction was found to be remarkable: a significant increase of the transformation from the original type to the B type and the AR type of spermatozoa. This finding suggests that $Ca^{2+}$-ATPase play an important role in the efflux and the influx of the $Ca^{2+}$ which have been known to be an essential factor for the capacitation and acrosome reaction, and that the inhibitory action of the $Ca^{2+}$-ATPase might be a prerequsit step toward the capacitation and acrosome reaction. In conclusion, this study suggest the considerable evidence as follows: the increment of the intracellular $Ca^{2+}$ concentration occurred by controlling the slope of $Ca^{2+}$ concentration through $Ca^{2+}$-ATPase activites in both the intracellular and extracellulr fluid may be important procedures for the capacitation and the acrosome reaction, and finally for fertilization of the sperm and ovum.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.294-294
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• 1994

To investigate analgesic mechanism of capsaicin and its analogues (capsaicinoids), release of adenosine was measured by high performance liquid chromatography from dorsal spinal cord synaptosomes, Exposure of synaptosomes to K$\^$+/ and morphine produced a dose dependent release of adenosine in the presence of Ca$\^$++/. Capsaicin (0.1, 1, 10 M), and its analogues 6-paradol (1, 10 M), NE-19550 (1, 10, 100 M), DMNE (1, 10, 100 M) and KR 25018 (0.1, 1, 10 M) produced a dose dependent release of adenosine in the presence of Ca$\^$++/. Nifedipine, L-type voltage sensitive calcium channel blocker, inhibited K$\^$+/ (6, 12 mM)- and morphine (10 M)-evoked release of adenosine completely, but inhibited capsaicin, and capsaicinoids-evoked release of adenosine partially. Capsazepine, a novel capsaicin select ive antagonist, blocked only capsaicin and capsaicinoids induced release of adenosine. Therefore, the adenosine release by capsaicin and capsaicinoids having antinociceptive effects involve activation of capsaicin specific receptor and capsaicin sensitive Ca$\^$++/ channel.

• YAKHAK HOEJI
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• v.43 no.1
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• pp.55-60
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• 1999

To investigate analgesic mechanism of capsaicin and its analogues (capaicinoids) adenosine release was measured by high performance liquid chromatography from rat spinal cord synaptosomes. Exposure of synaptosomes to $K^+$ and morphine produced a dose dependent release of adenosine in the presence of $Ca^{++}$. Capsaicin (0.1, 1, $10{\;}{\mu}M$), and its analogues: NE-19550 (1, 10, $100{\;}{\mu}M$), DMNE (1, 10, $100{\;}{\mu}M$) and KR 25018 (0.1, 1, $10{\;}{\mu}M$) produced a concentration dependent release of adenosine in the presence of $Ca^{++}$. Nifedifine, L-type voltage sensitive calcium channel blocker, inhibited $K^+$ (6, 12 mM)-and morphine ($10{\;}{\mu}M$)-evoked release of adenosine partially. Capsazepine, a novel capsaicin selective antagonist, blocked only capsaicin and capsaicinoids induced release of adenoside. Therefore, it is suggested that the adenosine release by capsaicin and capsaicinoids having antinociceptive effects involves actvation of capsaicin specific receptor and capsaicin sensitive $Ca^{++}$. channel.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.5
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• pp.467-475
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• 1997

Although one of the major physiological functions of taurine(2-aminoethanesulfonic acid) is the inhibitory action on the central nervous system(CNS), the mechanism of taurine in controlling the neuronal excitation in the CNS has been in controversy. Electrically evoked pEPSP and spontaneous activity induced by the perfusion of low $Mg^{++}-ACSF$ were recorded in the CA1 pyramidal cell layer of the hippocampal slice. To test the inhibitory effect of taurine on spontaneous responses, taurine was treated for 2 min at various concentrations(1 mM-10 mM). Taurine reduced the spontaneous activity by 22.2% at 1 mM, and 100% at 2 mM in low $Mg^{++}-ACSF$. Evoked response was induced by electrical stimulation of Schaffer collateral-commissural fibers. Taurine reduced the evoked response by 11.68% at 3 mM, and 24.25% at 5 mM. Even 20 mM of taurine reduced the evoked response only by 24 % after 5 min treatment. That is, the inhibitory efficacy was much higher in spontaneous activity than in evoked response. The $GABA_A$ receptor antagonist, 100 uM bicuculline, blocked the inhibitory action of taurine, while $GABA_B$ receptor antagonist, 700 uM phaclofen, did not. Taurine blocked the spontaneous activity in the presence of CNQX, and did not block the electrically evoked responce in the presence of APV. The results suggest that taurine causes hyperpolarization in the cell by binding to $GABA_A$ receptor and preferentially attenuates NMDA receptor-mediated hyperexcitation, leaving synaptic transmission unmodified.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.3
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• pp.279-286
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• 1998

It has been well documented that transient forebrain global ischemia causes selective neuronal degeneration in hippocampal CA1 pyramidal neurons with a delay of a few days. The mechanism of this delayed hippocampal CA1 pyramidal neuronal death (DND) is still controversial. To delineate the mechanisms of the DND, the effects of treatment with MK-801, an NMDA receptor antagonist, kynurenic acid, a NMDA/non-NMDA receptor antagonist, and/or cycloheximide, a protein synthesis inhibitor, on the DND were investigated in male Wistar rats. To examine the participation of apoptotic neuronal death in the DND, TUNEL staining was performed in ischemic brain section. Global ischemia was induced by 4-vessel occlusion for 20 min. All animals in this study showed the DND 3 and 7 days after the ischemic insult. The DND that occured 3 days and 7 days after the ischemia were not affected by pretreatment with MK-801 (1 mg/kg), but markedly attenuated by the pretreatment with kynurenic acid (500 mg/kg). Treatment with cycloheximide (1 mg/kg) also markedly inhibited the DND. The magnitudes of attenuation by the two drugs were similar. The magnitude of attenuation by co-treatments with kynurenic acid and cycloheximide was not greater than that with any single treatment. TUNEL staining was negative in the sections obtained 1 or 2 days after the ischemic insults, but it was positive at hippocampal CA1 pyramidal cells in sections collected 3 days after the ischemia. These results suggested that the DND should be mediated by the activation of non-NMDA receptor, not by the activation of NMDA receptor and that the activation of AMPA receptor should induce the apoptotic process in the DND.

• The Korean Journal of Physiology and Pharmacology
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• v.10 no.1
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• pp.25-30
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• 2006

Lysophosphatidylcholine (LPC), which accumulates in atherosclerotic arteries, has been reported to inhibit endothelium-dependent relaxation (EDR) in many different species. However, the underlying mechanism of LPC-induced inhibition of EDR is still uncertain. In the present study, we measured simultaneously both isometric tension and cytosolic free $Ca^{2+}$ ($[Ca^{2+}]_i$) in rabbit carotid strips, and examined the effect of LPC on tension and $[Ca^{2+}]_i$. In carotid strips with intact-endothelium, high $K^+$ (70 mM) increased both tension and $[Ca^{2+}]_i$, and cumulative addition of acetylcholine (ACh) from 0.1 to $10{\mu}M$ induced dose dependent increase of $[Ca^{2+}]_i$ with concomitant relaxation. In the presence of L-NAME (0.1 mM), ACh increased $[Ca^{2+}]_i$ without affecting the amplitude of high $K^+-induced$ tension. These ACh-induced change of $[Ca^{2+}]_i$ and tension was abolished by removal of endothelium or 10 nM 4-DAMP (muscarinic receptor antagonist) pretreatment. Pretreatment of LPC ($10{\mu}M$) inhibited ACh ($10{\mu}M$)-induced change of tension and $[Ca^{2+}]_i$ in endothelium-intact carotid artery. On the other hand, LPC had no effect on ACh-induced change of tension and $[Ca^{2+}]_i$ in endothelium denuded artery. In $Ca^{2+}$-free external solution, ACh transiently increased $[Ca^{2+}]_i$, and pretreatment of LPC significantly inhibited ACh-induced transient $[Ca^{2+}]_i$ change. Based on the above results, it may be concluded that LPC inhibits the ACh-induced $[Ca^{2+}]_i$ change through inhibition of $Ca^{2+}$ mobilization in vascular endothelial cells, resulting in decreased production of NO and concomitant inhibition of endotheliumdependent vascular relaxation.

• Molecules and Cells
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• v.37 no.9
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• pp.656-663
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• 2014

Gintonin, a novel, ginseng-derived G protein-coupled lysophosphatidic acid (LPA) receptor ligand, elicits $[Ca^{2+}]_i$ transients in neuronal and non-neuronal cells via pertussis toxin-sensitive and pertussis toxin-insensitive G proteins. The slowly activating delayed rectifier $K^+$ ($I_{Ks}$) channel is a cardiac $K^+$ channel composed of KCNQ1 and KCNE1 subunits. The C terminus of the KCNQ1 channel protein has two calmodulin-binding sites that are involved in regulating $I_{Ks}$ channels. In this study, we investigated the molecular mechanisms of gintonin-mediated activation of human $I_{Ks}$ channel activity by expressing human $I_{Ks}$ channels in Xenopus oocytes. We found that gintonin enhances $I_{Ks}$ channel currents in concentration- and voltage-dependent manners. The $EC_{50}$ for the $I_{Ks}$ channel was $0.05{\pm}0.01{\mu}g/ml$. Gintonin-mediated activation 1 of the $I_{Ks}$ channels was blocked by an LPA1/3 receptor antagonist, an active phospholipase C inhibitor, an $IP_3$ receptor antagonist, and the calcium chelator BAPTA. Gintonin-mediated activation of both the $I_{Ks}$ channel was also blocked by the calmodulin (CaM) blocker calmidazolium. Mutations in the KCNQ1 $[Ca^{2+}]_i$/CaM-binding IQ motif sites (S373P, W392R, or R539W)blocked the action of gintonin on $I_{Ks}$ channel. However, gintonin had no effect on hERG $K^+$ channel activity. These results show that gintonin-mediated enhancement of $I_{Ks}$ channel currents is achieved through binding of the $[Ca^{2+}]_i$/CaM complex to the C terminus of KCNQ1 subunit.

• Applied Biological Chemistry
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• v.39 no.3
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• pp.189-194
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• 1996

The effects of scorpion (Leiurus quinquestriatus hebraeus, Lqh) venom were evaluated on the activities of microsomal $Ca^{2+}-ATPase$ and $Ca^{2+}$ release channel prepared from the epithelial cells of pig airway. Whole venom of Lqh $(120\;{\mu}g/ml)$ increased the activity of microsomal $Ca^{2+}-ATPase$ about 32% in the tight-sealed microsomes and about 28% in the Triton X-100-treated or $Ca^{2+}$ ionophore A23187-treated leaky microsomes. Thapsigargin, a specific antagonist of $Ca^{2+}-ATPase$, inhibited 42% of total ATPase activity and also completely blocked the effects of Lqh venom, suggesting that Lqh venom directly activiates the microsomal $Ca^{2+}-ATPase$. In order to determine if Lqh venom increases the microsomal uptake of $^{45}Ca^{2+}$, Lqh venom was added in the uptake medium. The Lqh venom increased microsomal $^{45}Ca^{2+}$ uptake up to ${\sim}20%$ and the increase was only observed when heparin, an antagonist of $InsP_3$ receptor channel, was added in the uptake medium. Lqh venom in the absence of heparin unexpectedly decreased the rate and the amount of $^{45}Ca^{2+}$ uptake. These results were explained by simultaneous increases in $^{45}Ca^{2+}$ release as well as $^{45}Ca^{2+}$ uptake by Lqh venom. Lqh venom itself increased the release of $^{45}Ca^{2+}$ as much as $^{45}Ca^{2+}$ release by $4\;{\mu}m\;InsP_3$, implying that Lqh venom also activates $InsP_3$ receptor, microsomal $Ca^{2+}$ release channel. Based on these results, we suggest that the Lqh venom consists of at least two components; one activates the $InsP_3$ receptor and the other avates the $Ca^{2+}-ATPase$. Currently we a investigating the chemical and electrophysiological properties of the active components of Lqh venom.