• The Korean Journal of Physiology and Pharmacology
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• v.27 no.2
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• pp.187-196
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• 2023

Transient receptor potential canonical (TRPC) channels are non-selective calcium-permeable cation channels. It is suggested that TRPC4β is regulated by phospholipase C (PLC) signaling and is especially maintained by phosphatidylinositol 4,5-bisphosphate (PIP₂). In this study, we present the regulation mechanism of the TRPC4 channel with PIP₂ hydrolysis which is mediated by a channel-bound PLCδ1 but not by the G_qPCR signaling pathway. Our electrophysiological recordings demonstrate that the Ca²⁺ via an open TRPC4 channel activates PLCδ1 in the physiological range, and it causes the decrease of current amplitude. The existence of PLCδ1 accelerated PIP₂ depletion when the channel was activated by an agonist. Interestingly, PLCδ1 mutants which have lost the ability to regulate PIP₂ level failed to reduce the TRPC4 current amplitude. Our results demonstrate that TRPC4 self-regulates its activity by allowing Ca²⁺ ions into the cell and promoting the PIP₂ hydrolyzing activity of PLCδ1.

• Journal of Plant Biology
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• v.38 no.2
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• pp.195-201
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• 1995

The present study was made of the effects of abscisic acid(ABA) and calcium ions on dark respiration in protoplasts isolated from the basal intercalary meristematic tissues of oat (Avena sativa L.) seedlings. The influences of calcium channel blockers diitiazem(DTZ), verapamil(VPM), and $LaCl_2$ and the calmodulin antagonist trifluoperazine(TFP) on protoplast respiration activities were also investigated in order to evaluate the possible involvement of calcium channels and calmodulin during the dark respiration. The ABA only caused an 21% inhibition of protoplast respiration at $10^{-6}\;M$, but the extent of inhibition was very low by calcium treatments in the absence of ABA. In the presence of $10^{-6}\;M$ ABA, however, this inhibition of respiration increased by the increment of calcium ions concentrations. Treatments of DTZ and VPM were all found to restore the calcium-dependent inhibition of protoplast respiration by ABA and it was the same in thc $LaCl_2$ treatment except at $10^{-4}\;M$. At concentration from $10^{-6}\;M\;to\;10^{-4}\;M$, TFP also restored an inhibition of respiration. These results support the possibility that ABA increases plasmalemma permeability to calcium ions which might then bind to calmodulin to regulate oat protoplast dark respiration.ration.

• International Journal of Oral Biology
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• v.30 no.2
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• pp.71-76
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• 2005

The mesencephalic trigeminal nucleus (Mes V) contains cell bodies of primary afferent sensory neurons that relay proprioceptive information from the periodontium and masticatory muscles and function as typical sensory neurons or potentially as integrative interneurons. In the present study, we studied these two potential functions using combined experimental approaches of retrograde labeling and whole cell patch clamp recording. Mes V neurons that presumably originate from periodontal nerve fibers in subsets of Mes V nucleus were identified by retrograde labeling with a fluorescent dye, DiI, which was applied onto inferior alveolar nerve. These cells were elliptical perikarya shaped cells about $40{\mu}m$ in diameter. In these neurons, we measured high voltage-activated calcium channel (HVACC) currents. $GABA_B$ agonist, baclofen, inhibited calcium currents, and the HVACC currents inhibition by baclofen was voltage-dependent, exhibited prepulse facilitation, indicating that it was mediated by $G_i/_G_o$ protein. Taken together, our results demonstrate that Mes V neurons not only have cell bodies originating from periodontium, but also receive synaptic inputs including GABAergic neurons suggesting that Mes V neurons function as both primary sensory neurons and integrative interneurons.

• Archives of Pharmacal Research
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• v.25 no.4
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• pp.511-521
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• 2002

The purpose of this study was to determine whether bromocriptine affects the catecholamines (CA) secretion evoked in isolated perfused rat adrenal glands, by cholinergic stimulation, membrane depolarization and calcium mobilization, and to establish the mechanism of its action. The perfusion of bromocriptine ($1~10{\;}{\mu}M$) into an adrenal vein, for 60 min, produced relatively dose-dependent inhibition in the secretion of catecholamines (CA) evoked by acetylcholine (ACh, 5.32 mM), DMPP ($100{\;}{\mu}M$ for 2 min), McN-A-343 ($100{\;}{\mu}M$ for 2 min), cyclopiazonic acid (CPA, $10{\;}{\mu}M$ for 4 min) and Bay-K-8644 ($10{\;}{\mu}M$ for 4 min). High $K^+$ (56 mM)-evoked CA release was also inhibited, although not in a dose-dependent fashion. Also, in the presence of apomorphine ($100{\;}{\mu}M$), which is also known to be a selective $D_2$-agonist, the CA secretory responses evoked by ACh, high potassium, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly depressed. However, in adrenal glands preloaded with bromocriptine ($3{\;}{\mu}M$) in the presence of metoclopramide ($15{\;}{\mu}M$), a selective $D_2$-antagonist, the CA secretory responses evoked by ACh, high potassium, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid considerably recovered as compared to that of bromocriptine only. Taken together, these results suggest that bromocriptine can inhibit the CA secretion evoked by stimulation of cholinergic receptors, as well as by membrane depolarization, in the perfused rat adrenal medulla. It is thought this inhibitory effect of bromocriptine may be mediated by inhibiting the influx of extracellular calcium and the release from intracellular calcium stores, through the activation of dopaminergic $D_2$-receptors located in the rat adrenomedullary chromaffin cells. Furthermore, these findings also suggest that the dopaminergic $D_2$-receptors may play an important role in regulating adrenomedullary CA secretion.

• YAKHAK HOEJI
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• v.43 no.5
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• pp.659-664
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• 1999

To investigate the difference of contractile mechanism between KCI and phenylephrine-induced contraction, we observed effects of $Ca^{2+}$ antagonists and protein kinase inhibitors on aorta contraction of rats. Verapamil dose-dependently inhibited the contraction induced by KCI and phenylephrine, the inhibitory effect of verapamil was more potent in KCI-induced contraction than phenylephrine-induced contraction. Econazole and TMB-8 significantly inhibited CKI-induced contraction but did not inhibit phenylephrine-induced contraction. Staurosporine dose-dependently inhibited both KCI and phenylephrine-induced contraction. Genistein and calmodulin antagonists (W-7 and trifluoperazine) also inhibited both contraction in a dose dependent manner. However, the inhibitory effects of genistein and calmodulin antagonists were more potent in phenylephrine-induced contraction than KCI-induced contraction. These results suggest that involvements of $Ca^{2+}$ channel and protein kinase in rat aorta contraction were dependent on agonist causing aorta smooth muscle contraction.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.5
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• pp.311-316
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• 2010

It is well-known that electrical field stimulation (EFS)-induced contraction is mediated by a cholinergic mechanism and other neurotransmitters. NO, ATP, calcitonin gene-related peptide (CGRP), and substance P are released by EFS. To investigate the purinergic mechanism involved in the EFS-induced contraction, purinegic receptors antagonists were used. Suramine, a non-selective P2 receptor antagonist, reduced the contraction induced by EFS. NF023 ($10^{-7}{\sim}10^{-4}M$), a selective P2X antagonist, inhibited the contraction evoked by EFS. Reactive blue ($10^{-6}{\sim}10^{-4}M$), selective P2Y antagonist, also blocked the contraction in a dose-dependent manner. In addition, P2X agonist ${\alpha}$,${\beta}$-methylene 5'-adenosine triphosphate (${\alpha}{\beta}MeATP$, $10^{-7}{\sim}10^{-5}M$) potentiated EFS-induced contraction in a dose-dependent manner. P2Y agonist adenosine 5'-[${\beta}$-thio]diphosphate trilithium salt ($ADP{\beta}S$, $10^{-7}{\sim}10^{-5}M$) also potentiated EFS-induced contractions in a dose-dependent manner. Ecto-ATPase activator apyrase (5 and 10 U/ml) reduced EFS-induced contractions. Inversely, 6-N,$N$-diethyl-D-${\beta}$,${\gamma}$- dibromomethylene 5'-triphosphate triammonium (ARL 67156, $10^{-4}M$) increased EFS-induced contraction. These data suggest that endogenous ATP plays a role in EFS-induced contractions which are mediated through both P2X-receptors and P2Y-receptors stimulation in cat esophageal smooth muscle.

• Development and Reproduction
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• v.3 no.1
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• pp.87-93
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• 1999

The possible role of Na$^{+}$/H$^{+}$ antiporter in both the capacitation and the acrosome reaction (AR) was examined in mouse epididymal spermatozoa. Spontaneous acrosome reaction was inhibited by dimethyl amiloride (DMA), a specific inhibitor of Na$^{+}$/H$^{+}$ antiporter, with dose dependent manner. Follicular fluid- or A23l 87-induced acrosome reaction was not inhibited by DMA. It suggests that change in pH$_{i}$ by monovalent cation transport through the Na$^{+}$/H$^{+}$ antiporter is possibly engaged in the capacitation and that agonist- as well as A23l87-induced AR in capacitated sperm might be independent from the Na$^{+}$/H$^{+}$ antiporter. Conclusively, changes in pH$_{i}$ through the Na$^{+}$/H$^{+}$ antiporter might be important for sperm capacitation and it virtually occurs upstream of the $Ca^{2+}$ influx which precedes the acrosome reaction in mouse epididymal spermatozoa.pididymal spermatozoa.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.3
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• pp.229-239
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• 2009

The aim of the present study was to examine the effect of provinol, which is a mixture of polyphenolic compounds from red wine, on the secretion of catecholamines (CA) from isolated perfused rat adrenal medulla, and to elucidate its mechanism of action. Provinol (0.3 ${\sim}$ 3 ${\mu}g/ml$) perfused into an adrenal vein for 90 min dose- and time-dependently inhibited the CA secretory responses evoked by ACh (5.32 mM), high $K^+$ (a direct membrane-depolarizer, 56 mM), DMPP (a selective neuronal nicotinic $N_N$ receptor agonist, 100 ${\mu}M$) and McN-A-343 (a selective muscarinic $M_1$ receptor agonist, 100 ${\mu}M$). Provinol itself did not affect basal CA secretion. Also, in the presence of provinol (1 ${\mu}g/ml$), the secretory responses of CA evoked by Bay-K-8644 (a voltage-dependent L-type dihydropyridine $Ca^{2+}$ channel activator, 10 ${\mu}M$), cyclopiazonic acid (a cytoplasmic $Ca^{2+}$-ATPase inhibitor, 10 ${\mu}M$) and veratridine (an activator of voltage-dependent $Na^+$ channels, 10 ${\mu}M$) were significantly reduced. Interestingly, in the simultaneous presence of provinol (1 ${\mu}g/ml$) plus L-NAME (a selective inhibitor of NO synthase, 30 ${\mu}M$), the CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclpiazonic acid recovered to the considerable extent of the corresponding control secretion in comparison with the inhibition of provinol-treatment alone. Under the same condition, the level of NO released from adrenal medulla after the treatment of provinol (3 ${\mu}g/ml$) was greatly elevated in comparison to its basal release. Taken together, these data demonstrate that provinol inhibits the CA secretory responses evoked by stimulation of cholinergic (both muscarinic and nicotinic) receptors as well as by direct membrane-depolarization from the perfused rat adrenal medulla. This inhibitory effect of provinol seems to be exerted by inhibiting the influx of both calcium and sodium into the rat adrenal medullary cells along with the blockade of $Ca^{2+}$ release from the cytoplasmic calcium store at least partly through the increased NO production due to the activation of nitric oxide synthase.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.2
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• pp.43-49
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• 2008

Flavonoids have been shown to affect calcium signaling in neurons. However, there are no reports on the effect of apigenin on glutamate-induced calcium signaling in neurons. We investigated whether apigenin affects glutamate-induced increase of free intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) in cultured rat hippocampal neurons, using fura-2-based digital calcium imaging and microfluorimetry. The hippocampal neurons were used between 10 and 13 days in culture from embryonic day 18 rats. Pretreatment of the cells with apigenin ($1{\mu}M$ to $100{\mu}M$) for 5 min inhibited glutamate ($100{\mu}M$, 1 min) induced $[Ca^{2+}]_i$ increase, concentration-dependently. Pretreatment with apigenin ($30{\mu}M$) for 5 min significantly decreased the $[Ca^{2+}]_i$ responses induced by two ionotropic glutamate receptor agonists, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA, $10{\mu}M$, 1 min) and N-methyl-D-aspartate (NMDA, $100{\mu}M$, 1 min), and significantly inhibited the AMPA-induced peak currents. Treatment with apigenin also significantly inhibited the $[Ca^{2+}]_i$ response induced by 50 mM KCl solution, decreased the $[Ca^{2+}]_i$ responses induced by the metabotropic glutamate receptor agonist, (S)-3,5-dihydroxy-phenylglycine (DHPG, 100 $[Ca^{2+}]_i$, 90 s), and inhibited the caffeine (10 mM, 2 min)-induced $[Ca^{2+}]_i$ responses. Furthermore, treatment with apigenin ($30{\mu}M$) significantly inhibited the amplitude and frequency of 0.1 mM $[Mg^{2+}]_o$-induced $[Ca^{2+}]_i$ spikes. These data together suggest that apigenin inhibits glutamate-induced calcium signaling in cultured rat hippocampal neurons.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.4
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• pp.223-230
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• 2005

The purpose of the present study was to examine the effect of naltrexone, an opioid antagonist, on secretion of catecholamines (CA) evoked by cholinergic nicotinic stimulation and membrane-depolarization from the isolated perfused rat adrenal gland and to establish the mechanism of its action. Naltrexone $(3{\times}10^{-6}M)$ perfused into an adrenal vein for 60 min produced time-dependent inhibition in CA secretory responses evoked by ACh $(5.32{\times}10^{-3}M)$ , high $K^+$ $(5.6{\times}10^{-2}M)$ , DMPP ($10^{-4}$ M) and McN-A-343 $(10^{-4}M)$ . Naltrexone itself did also fail to affect basal CA output. In adrenal glands loaded with naltrexone $(3{\times}10^{-6}M)$ , the CA secretory responses evoked by Bay-K-8644, an activator of L-type $Ca^{2+}$ channels and cyclopiazonic acid, an inhibitor of cytoplasmic $Ca^{2+}-ATPase$, were also inhibited. However, in the presence of met-enkephalin $(5{\times}10^{-6}M)$ , a well-known opioid agonist, the CA secretory responses evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644 and cyclopiazonic acid were also significantly inhibited. Collectively, these experimental results demonstrate that naltrexone inhibits greatly CA secretion evoked by stimulation of cholinergic (both nicotinic and muscarinic) receptors as well as that by membrane depolarization. It seems that this inhibitory effect of naltrexone does not involve opioid receptors, but might be mediated by blocking both the calcium influx into the rat adrenal medullary chromaffin cells and the uptake of $Ca^{2+}$ into the cytoplasmic calcium store, which are at least partly relevant to the direct interaction with the nicotinic receptor itself.