• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.147-154
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• 1998

It was attempted to clarify the participation of $K^+-channels$ in the post-receptor mechanisms of the muscarinic and $A_1-adenosine$ receptor- mediated control of acetylcholine (ACh) release in the present study. Slices from the rat hippocampus were equilibrated with $[^3H]$choline and the release of the labelled products was evoked by electrical stimulation (3 Hz, 5 V/cm, 2 ms, rectangular pulses), and the influence of various agents on the evoked tritium-outflow was investigated. Oxotremorine (Oxo, $0.1{\sim}10\;{\mu}M$), a muscarinic agonist, and $N^6-cyclopentyladenosine$ (CPA, $1{\sim}30\;{\mu}M$), a specific $A_1-adenosine$ agonist, decreased the ACh release in a dose-dependent manner, without affecting the basal rate of release. 4-aminopyridine (4AP), a specific A-type $K^+-channel$ blocker ($1{\sim}100\;{\mu}M$), increased the evoked ACh release in a dose-related fashion, and the basal rate of release is increased by 3 and $100\;{\mu}M$. Tetraethylammonium (TEA), a non-specific $K^+-channel$ blocker ($0.1{\sim}10\;{\mu}M$), increased the evoked ACh release in a dose-dependent manner without affecting the basal release. The effects of Oxo and CPA were not affected by $3\;{\mu}M$ 4AP co-treatment, but 10 mM TEA significantly inhibited the effects of Oxo and CPA. 4AP ($10\;{\mu}M$)- and TEA (10 mM)-induced increments of evoked ACh release were completely abolished in Ca^{2+}-free$ medium, but these were recoverd in low Ca^{2+}$ medium. And the effects of $K^+-channel$ blockers in low Ca^{2+}$ medium were inhibited by $Mg^{2+}$ (4 mM) and abolished by $0.3\;{\mu}M$ tetrodotoxin (TTX). These results suggest that the changes in TEA-sensitive potassium channel permeability and the consequent limitation of Ca^{2+}$ influx are partly involved in the presynaptic modulation of the evoked ACh-release by muscarinic and $A_1-adenosine$ receptors of the rat hippocampus.

• The Korean Journal of Physiology
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• v.29 no.2
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• pp.203-216
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• 1995

The effects of ${\alpha}_1-adrenergic$ receptor stimulation on membrane potential, intracellular $Na^+$ activity, and twitch force were investigated in ventricular muscles from guinea-pig hearts. Action potentials, intracellular $Na^+$ activity, and twitch force of ventricular papillary muscles were measured simultaneously under various experimental conditions. Stimulation of the ${\alpha}_1-adrenergic$ receptor by phenylephrine produced variable changes in action potential duration, a slight hyperpolarization of the diastolic membrane potential, a decrease in intracellular $Na^+$ activity, and a biphasic inotropic response in which a transient negative inotropic response was followed by a sustained positive inotropic response. These changes were blocked by prazosin, an antagonist of the ${\alpha}_1-adrenergic$ receptor, but not by atenolol, an antagonist of the ${\beta}-adrenergic$ receptor. This indicates that the changes in membrane potential, intracellular $Na^+$ activity, and twitch force are mediated by stimulation of the ${\alpha}_1-adrenergic$ receptor, but not by stimulation of ${\beta}-adrenergic$ receptor. The decrease in intracellular $Na^+$ activity was not observed in quiescent muscles, depending on the rate of the action pontentials in beating muscles. The intracellular $Na^+$ activity decrease was substantially inhibited by tetrodotoxin. However, the decrease in intracellular $Na^+$ activity was not affected by an inhibition of the $Na^+-K^+$ pump. Therefore, the decrease in intracellular $Na^+$ activity mediated by the ${\alpha}_1-adrenergic$ receptor appears to be due to a reduction of $Na^+$ influx during the action potential, perhaps through tetrodotoxin sensitive $Na^+$ channels. Our study also revealed that the decrease in intracellular $Na^+$ activity might be related to the transient negative inotropic response. The intracellular $Na^+$ activity decrease could lower intracellular $Ca^{2+}$ through the $Na^+-Ca^{2+}$ exchanger and thereby produce a decline in twitch force.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.1
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• pp.97-105
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• 1997

The regulatory role of cyclic nucleotides in the expression of neutrophil responses has been examined. fMLP-stimulated superoxide production in neutrophils was inhibited by dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), histamine, adenosine + theophylline, cAMP elevating agents, and 8-bromoguanosine 3' ,5' -cyclic monophosphate (8-BrcGMP) and sodium nitroprusside, cGMP elevating agents. Staurosporine, a protein kinase C inhibitor, genistein, a protein tyrosine kinase inhibitor and chlorpromazine, a calmodulin inhibitor, inhibited superoxide production by fMLP, but they did not further affect the action of DBcAMP on the stimulatory action of fMLP. DBcAMP, histamine, adenosine+theophylline and genistein inhibited myeloperoxidease release evoked by fMLP, whereas BrcGMP, sodium nitroprusside and staurosporine did not affect it. The elevation of $[Ca^{2+}]_i$ evoked by fMLP was inhibited by genistein and chlorpromazine but was not affected by staurosporine. DBcAMP exerted little effect on the initial peak in $[Ca^{2+}]_i$ response to fMLP but effectively inhibited the sustained rise. On the other hand, BrcGMP significantly inhibited both phases. fMLP-induced $Mn^{2+}$ influx was inhibited by either DBcAMP or BrcGMP. These results suggest that fMLP-stimulated neutrophil responses may be regulated by cAMP more than cGMP. cAMP and cGMP appear not affect stimulated responses by direct protein kinase C activation. Their regulatory action on the stimulated neutrophil responses may be not influenced by other activation processes.

• The Korean Journal of Pharmacology
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• v.17 no.2
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• pp.7-16
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• 1981

Higenamine ($Ca_{26}H_{17}No_3$. HCI, d1-1- (4-hydroxybenzyl) -6,7-dihydroxy-1,2,3,4-tetrahydroiso-quinoline hydrochloride), which has recently teen isolated from the Aconite root, was known to the cardiotonic component of the Aconite root. The positive inotropic effect of Higenamine was observed in the isolated electrically driven left atrium from rabbits with respect to the influences of extracellular calcium and of calcium antagonists, e.g. $La^{+++}$ and verapamil. A synergistic relation in the positive inotropic effect could be demonstrated between Higenamine and extra cellular calcium. The inotropic potency of $10^{-7}\;g/ml$ Higenamine was equivalant to that of 0.058 mM of calcium in the medium. In the preparation, of which contractility had been reduced by the treatment of $La^{+++}(10^{-5}-10^{-4}M)$ and verapamil$(2{\times}10^{-7}-10^{-6}M)$, Higenamine was able to restore the contractility. These results indicated that one of the possible mechanism of positive inotropism of Higenamine was to accelerate the influx of calcium from the extracellular space through the sarcolemma.

• Natural Product Sciences
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• v.25 no.2
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• pp.165-171
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• 2019

Although the functions of a standardized extract of Gingko biloba leaves (EGb $761^{(R)}$) has been reported with regard to neurobiological properties, no attention has been paid to the impact of EGb $761^{(R)}$ on the neuronal regulation of energy homeostasis. To evaluate the hypothesis that EGb $761^{(R)}$ affect the secretion of peptide tyrosine tyrosine (PYY) and the activation of free fatty acid receptor 4 (FFA4), which are involved in the neuronal circuitries that control energy homeostasis by inducing the transfer of information about the influx of energy to the brain, we examined whether EGb $761^{(R)}$ can stimulate PYY secretion in the enteroendocrine NCI-H716 cells and if EGb $761^{(R)}$ can activate FFA4 in FFA4-expressing cells. In NCI-H716 cells, EGb $761^{(R)}$ stimulated PYY secretion and the EGb $761^{(R)}$-induced PYY secretion was involved in the increase in intracellular $Ca^{2+}$ concentration and the activation of FFA4. Furthermore, in FFA4-expressing cells, EGb $761^{(R)}$ activated FFA4. These results suggest that EGb $761^{(R)}$ may affect the control of energy homeostasis via the regulation of PYY secretion and FFA4 activation.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.47-56
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• 2008

Risperidone is a widely prescribed atypical antipsychotic agent. Approved by the FDA as the first drug to treat irritability associated with autism in children, it is also used to treat tic disorder and Tourette's syndrome. Its adverse reactions related to dentistry include dry mouth, the mechanism of which is yet to be identified. The aim of this study is to identify, at the cellular level, how and to what extent risperidone affects intracellular free calcium concentration ($[Ca^{2+}]_i$), an primary intracellular factor in the regulation of fluid secretion in salivary gland cells. The human salivary gland cell line (HSG) was grown in MEM supplemented with 10% BCS. In order to measure $[Ca^{2+}]_i$, Fura-2/AM was loaded in the HSG, and fluorescence at 340 nm/380 nm excitation was measured in the 500 nm emission ratio. After every experiment, a calibration experiment was conducted in order to readjust the ratio to the actual $[Ca^{2+}]_i$. Changes in $[Ca^{2+}]_i$ were measured in the presence of carbachol, ATP and histamine. The researcher then explored how the pretreatment of risperidone affected such changes. Findings of this study include: 1. In HSG, $[Ca^{2+}]_i$ increased due to the addition of carbachol, ATP and histamine. The presence of risperidone inhibited the action of histamine on this process, while making little effect on that of carbachol and ATP. 2. A quantification of $[Ca^{2+}]_i$ in relation to histamine of different concentrations indicates that the effect of histamine was concentration dependent with an $EC_{50}$ of $3.3{\pm}0.5\;{\mu}M$. 3. The inhibitory effect of risperidone on histamine-induced $[Ca^{2+}]_i$ was concentration-dependent with an $IC_{50}$ of $104.4{\pm}14\;nM$. 4. Risperidone inhibits histamine-induced Ca2+ release from endoplasmic reticulum and influx of extracellular $Ca^{2+}$ in HSG cells(p<0.05).

• Korean Journal of Veterinary Research
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• v.46 no.2
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• pp.87-96
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• 2006

We established an in vitro experimental system using the following procedure. We first introduced tritium-labeled norepinephrine ([$^3$H]-NE) into PC12 cells, The [$^3$H]-NE incorporated into PC12 cells were then stimulated by a high concentration (60 mM) of $K^+$ buffer during 12 minutes. Then, we collected $100{\mu}l$ supernatant and counted the amount of [$^3$H]-NE release from PC12 cells with a scintillation counter. After screening fungal, Streptomyces spp. or bacterial product using this experimental sytem, we obtained FS11052 from Streptomyces spp. which inhibited [$^3$H]-NE release from PC12 cells. FS11052 also inhibits the release of ATP as a neurotransmitter of PC12 cells and rat cortical neurons, The inhibitory effect was seen even when the PC12 cells were treated with low $K^-$ buffer containing ionomycin ($1{\mu}M$) as an ionopore. This result suggests that the inhibitory action of FS11052 on neurotransmitter release appeared after the influx of $Ca^{2+}$.

• Journal of Embryo Transfer
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• v.21 no.1
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• pp.35-43
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• 2006

Ions play important roles in various cellular processes including fertilization and differentiation. However, it is little known whether how ions are regulated during early embryonic development in mammalian animals. In this study, we examined changes in $Ca^{2+}\;and\;K^+$ concentrations in embryos and oviduct during mouse early embryonic development using patch clamp technique and confocal laser scanning microscopy. The intracellular calcium concentration in each stage embryos did not markedly change. At 56h afier hCG injection when 8-cell embryos could be Isolated from oviduct, $K^+$ concentration in oviduct increased by 26% compared with that at 14h after injection of hCG During early embryonic development, membrane potential was depolarized (from -38 mV to -16 mV), and $Ca^{2+}$ currents decreased, indicating that some $K^+$ channel might control membrane potential in oocytes. To record the changes in membrane potential induced by influx of $Ca^{2+}$ in mouse oocytes, we applied 5 mM $Ca^{2+}$ to the bath solution. The membrane potential transiently hyperpolarized and then recovered. In order to classify $K^+$ channels that cause hyperpolarization, we first applied TEA and apamin, general $K^+$ channel blockers, to the bath solution. Interestingly, the hyperpolarization of membrane potential still appeared in oocytes pretreated with TEA and apamin. This result suggest that the $K^+$ channel that induces hyperpolarization could belong to another $K^+$ channel such as two-pore domain $K^+(K_{2P})$channel that a.e insensitive to TEA and apamin. From these results, we suggest that the changes in $Ca^{2+}\;and\;K^+$ concentrations play a critical role in cell proliferation, differentiation and reproduction as well as early embryonic development, and $K_{2P}$ channels could be involved in regulation of membrane potential in ovulated oocytes.

• Toxicological Research
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• v.14 no.3
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• pp.341-348
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• 1998

We established an in vitro experimental system using the following procedure. We first introduced tritium-labelled norepinephrine ([3H]-NE)into PC12 cells. The [3H]-NE incorporated into PC12 cells were then stimulated by a high concentration (60 mM) of $K^+$ during 12 minutes. Then, we counted the amount of [3H]-NE release from PC12 cells with the scintillation counter. After screening fungal, Streptomyces or bacterial product using this experimental system, we obtained S9940 from Streptomyces spp. which inhibited [3H]-NE release from PC12 cells. S9940 also inhibits the release of ATP as a neurotransmitter of PC12 cells and rat cortical neurons. The inhibitory effect was seen even when the PC12 cells were treated with low $K^+$ buffer containing ionomycin $(1\muM)$ as an ionopore. This result suggests that the inhibitory action of S9940 on neurotransmitter release appeared after the influx of $Ca^{2+}$.

• BMB Reports
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• v.29 no.1
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• pp.11-16
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• 1996

The present study showed that receptor-mediated activation of rabbit kidney proximal tubule cells by angiotensin II, the $Ca^{2+}$ ionophore A23187, or the protein kinase C activator phorbol myristate acetate (PMA) all stimulated phospholipase D (PLD). This was demonstrated by the increased formation of phosphatidic acid, and in the presence of 0.5% ethanol, phosphatidylethanol (PEt) accumulation. Angiotensin II leads to a rapid increase in phosphatidic acid and diacylglycerol, and phosphatidic acid formation preceeded the formation of diacylglycerol. This result suggests that some phosphatidic acid seems to be formed directly from phosphatidylcholine hydrolyzed by Pill. On the other hand, EGTA substantially attenuated angiotensin II and A23187-induced PEt formation, and when the cells were pretreated with verapamil angiotensin II-induced Pill activation was completely abolished. These results provide the evidence that calcium ion influx is essential for the agonist-induced Pill activation. In addition, staurosporine, an inhibitor of protein kinase C, strongly inhibited PMA-induced PEt formation, but was ineffective on angiotensin II-induced PEt accumulation. $GTP{\gamma}S$ also stimulates PEt formation in digitonin-permeabilized cells, but pretreatment of the cells with pertussis toxin failed to suppress angiotensin II-induced PEt formation. From these results, we conclude that in the rabbit kidney proximal tubule cells the mechanisms of angiotensin II- and PMA-induced Pill activation are different from each other and mediated via a pertussis toxin-insensitive trimeric G protein.