• The Korean Journal of Physiology and Pharmacology
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• v.2 no.2
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• pp.225-232
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• 1998

To investigate the possible involvement of outward potassium ($K^+$) currents in nitric oxide-induced relaxation in intestinal smooth muscle, we used whole-cell patch clamp technique in freshly dispersed guinea-pig ileum longitudinal smooth muscle cells. When cells were held at -60 mV and depolarized from -40 mV to -50 mV in 10 mV increments, sustained outward $K^+$ currents were evoked. The outward $K^+$ currents were markedly increased by the addition of 10 ${\mu}M$ sodium nitroprusside (SNP). 10 ${\mu}M$ S-nitroso-N-acetylpenicillamine (SNAP) and 1 mM 8-Bromo-cyclic GMP (8-Br-cGMP) also showed a similar effect to that of SNP. 1 mM tetraethylammonium (TEA) significantly reduced depolarization-activated outward $K^+$ currents. SNP-enhanced outward $K^+$ currents were blocked by the application of TEA. High EGTA containing pipette solution (10 mM) reduced the control currents and also inhibited the SNP-enhanced outward $K^+$ currents. 5 mM 4-aminopyridine (4-AP) significantly reduced the control currents but showed no effect on SNP-enhanced outward $K^+$ currents. 0.3 ${\mu}M$ apamin and 10 ${\mu}M$ glibenclamide showed no effect on SNP-enhanced outward $K^+$ currents. 10 ${\mu}M$ 1H-[1,2,4]oxadiazolo [4,3-a]quinoxaline-1-one (ODQ), a specific inhibitor of soluble guanylate cyclase, significantly blocked SNP-enhanced $K^+$ currents. We conclude that NO donors activate the $Ca^{2+}-activated$ $K^+$ channels in guinea-pig ileal smooth muscle via activation of guanylate cyclase.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.2
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• pp.169-183
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• 1997

We have investigated the two types of voltage-dependent outward potassium (K) currents, i.e. delayed rectifier K current ($I_{K(V)}$) and 'A-like' transient outward K current ($I_{to}$) with patch-clamp technique in single smooth muscle cells (SMCs) isolated from rabbit basilar artery, and investigated the characteristics of them. The time-courses of activation were well fitted by exponential function raised to second power ($n^2$) in $I_{K(V)}$ and fourth power ($n^4$) in $I_{to}$. The activation, inactivation and recovery time courses of $I_{to}$ were much faster than that of $I_{K(V)}$. The steady-state activation and inactivation of $I_{K(V)}$ was at the more hyperpolarized range than that of $I_{to}$ contrary to the reports in other vascular SMCs. Tetraethylammonium chloride (TEA; 10 mM) markedly inhibited $I_{K(V)}$ but little affected $I_{to}$. 4-Aminopyridine (4-AP) had similar inhibitory potency on both currents. While a low concentration of $Cd^{2+}$ (0.5 mM) shifted the current- voltage relationship of $I_{to}$ to the positive direction without change of maximum conductance, $Cd^{2+}$ did not cause any appreciable change for $I_{K(V)}$.

• Journal of the Korean Chemical Society
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• v.53 no.3
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• pp.308-324
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• 2009

The present work is devoted to study the interaction of $\beta$-aroylacrylic acid derivative (3) with malononitrile in (DMF) in the presence of piperidine and/or ammonium acetate, then using the formed compounds as starting materials for synthesizing fused and isolated heterocyclic systems. It has been established that the $\beta$-aroylacrylic acid (3) reacts with malononitrile in (DMF) in the presence of piperidine as a catalyst with the formation of 4H-pyran derivative (4). By changing the catalyst into ammonium acetate, pyridine derivative (5) has been obtained. Also the N-maleamic acid derivatives (19) and (27) have been synthesized via the interaction of (4) and (5) with maleic anhydride. The purpose of this step is to study the behavior of the formed maleamic acid derivatives – as analogies of $\beta$-aroylacrylic acids – towards different active methylene compounds under Michael addition reaction.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.2
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• pp.73-77
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• 2008

Recent studies have documented that testosterone relaxes several smooth muscles by modulating $K^+$ channel activities. Smooth muscles of seminal vesicles playa fundamental role in ejaculation, which might involve testosterone. This study was aimed to assess the role of testosterone in seminal vesicular motility by studying its effects on contractile agents and on the ion channels of single vesicular myocytes in a rabbit model. The contractile responses of circular smooth muscle strips of rabbit seminal vesicles to norepinephrine ($10{\mu}M$), a high concentration of KCI (70 mM), and testosterone ($10{\mu}M$) were observed. Single vesicular myocytes of rabbit were isolated using proteolytic enzymes including collagenase and papain. Inside-out, attached, and whole-cell configurations were examined using the patch clamp technique. The applications of $10{\mu}M$ norepinephrine or 70 mM KCl induced tonic contractions, and $10{\mu}M$ testosterone (pharmacological concentration) evoked dose-dependent relaxations of these precontracted strips. Various $K^+$ channel blockers, such as tetraethylammonium (TEA; $10{\mu}M$), iberiotoxin ($0.1{\mu}M$), 4-aminopyridine (4-AP, $10{\mu}M$), or glibenclamide ($10{\mu}M$) rarely affected these relaxations. Single channel data (of inside-out and attached configurations) of BK channel activity were also hardly affected by testosterone ($10{\mu}M$). On the other hand, however, testosterone reduced L-type $Ca^{2+}$ currents significantly, and found to induce acute relaxation of seminal vesicular smooth muscle and this was mediated, at least in part, by $Ca^{2+}$ current inhibition in rabbit.

• Journal of the Korean Chemical Society
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• v.30 no.2
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• pp.145-151
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• 1986

Using a new conductometric method, dissociation constants of 3-cyano, 4-cyano, 3-amino and 4-aminopyridine were measured in the temperature range 15 ∼ 40${\circ}C$ and pressure up to 2500bar in aqueous media. This method is convenient to apply to the low dissociative acid and base but have to do tedious extrapolating procedure for the ionic conductance in elaborated temperatures and pressures and have to know any reference dissociation constant. The measured dissociation constants were increased as the temperature increase but decreased as the pressure increase. From the constants, various thermodynamic properties were evaluated and discussed for the dissociation reactions.

• Animal cells and systems
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• v.1 no.1
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• pp.81-86
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• 1997

We studied the mechanism of arachidonic acid on the secretion of a neurotransmitter in rat pheochromocytoma PC12 cells. Arachidonic acid inhibited the 70 mM $K^+$-induced secretion of norepinephrine. Arachidonic acid also inhibited the 70 mM $K^+$-induced $Ca^{2+}$ mobilization which is due to the opening of the voltage-sensitive $Ca^{2+}$ channels (VSCC). Both the half maximal inhibitory concentration ($IC_{50}$) of the norepinephrine secretion and VSCC coincided at 30 uM. The major oxidized metabolites of arachidonic acid, prostaglandins did not mimic the inhibitory effect of arachidonic acid. Nordihydroguaiaretic acid (NDGA) and indomethacin which are inhibitors of lipoxygenase and cyclooxygenase, respectively, did not block the inhibitory effect of arachidonic acid. The results suggest that arachidonic acid serves as a signal itself, not in the form of metabolites. The pretreatment of various $K^+$ channel blockers such as 4-aminopyridine, tetraethylarnmonium, glipizide, or glibenclamide also did not show any effect on the inhibitory effect of arachidonic acid. Through these results we suggest that arachidonic acid regulates VSCC directly and affects the secretion of neurotransmitters.

• The Korean Journal of Pharmacology
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• v.27 no.2
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• pp.99-108
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• 1991

The effect of racemic Ketamine HCl was observed on excitable membranes of sciatic nerve fibres and toe muscles from frog. Ketamine significantly depressed the amplitude of the action potential, maximum rate of rise and that of fall of action potentials of sciatic nerve by dose-dependent and time-course manner, and also it produced the inhibition of $K^+-contracture$ in toe muscle. We used two different ways of sucrose gap method to to obtain the better results from sciatic nerve. We observed and compared the effect of ketamine on sciatic nerve with naloxone, 4-AP (4-aminopyridine) and TEA (Tetraethylammonium). Naloxone significantly but not totally blocked the effect of ketamine both on nerve and on skeletal muscle. 4-AP or TEA by itself had a significant depressant effect on the action potentials on nerve by central perfusion (extracellular perfusion), but both of these drugs did not much affect the action of Ketamine on nerve. The reversibility of effect of Ketamine (10 mM) was observed both on nerve and on skeletal muscles when exposed to drug for short duration. The effects of racemic ketamine described may provide to support that one of the mechanisms of the action of Ketamine on nerve and on muscles of frog might be related to non-specifically effect on receptors within the ion channels $(K^+-channel,\;Na^+-channel\;or\;slow\;Ca^{++}\;channel)$ at higher dose which produces anesthetic effect and also it interacts specifically with one of the opioid receptors or subtype of these receptors which is sensitive to Naloxone at lower dose which produces analgesia.

• The Korean Journal of Physiology
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• v.26 no.1
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• pp.27-35
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• 1992

We used the whole cell patch clamp technique to examine the ionic basis for the tail current after depolarizing pulse in single atrial myocytes of the rabbit. We recorded the tail currents during various repolarizations after short depolarizing pulse from a holding potential of -70 mV. The potassium currents were blocked by external 4-aminopyridine and replacement of internal potassium with cesium. The current was reversed to the outward direction above +10 mV. High concentrations of intracellular calcium buffer inhibited the activation of the current. Diltiazem and ryanodine blocked it too. These data suggest that the current is activated by intracellular calcium released from sarcoplasmic reticulumn. When the internal chloride concentration was increased, the inward tail current was increased. The current was partially blocked by the anion transport blocker niflumic acid. The current voltage curve of the niflumic acid sensitive current component shows outward rectification and is well fitted to the current voltage curve of the theoretically predicted chloride current calculated from the constant field equation. The currents recorded in rabbit atrial myocytes, with the method showing isolated outward Na Ca exchange current in ventricular cells of the guinea pig, suggested that chloride conductance could be activated with the activation of Na/ca exchange current. From the above results it is concluded that a chloride sensitive component which is activated by intracellular calcium contributes to tail currents in rabbit atrial cells.

• YAKHAK HOEJI
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• v.41 no.4
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• pp.399-406
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• 1997

The effects of different $K^+$ channel blockers were investigated on the non-adrenergic non-cholinergic (NANC) relaxations in the circular muscle of the rabbit proximal stomach. Non-selective blockers of $K^+$ channels, 4-aminopyridine (4-AP, 3~30${\mu}M$) and tetraethylammonium (TEA, 100~1000${\mu}M$) significantly enhanced the NANC relaxations in a concentration-dependent manner. The enhancement was more prominent for the NANC relaxations induced by the electric field stimulation (EFS) with lower frequencies. Blockers of large conductance $Ca^{2+}$-activated $K^+$ channels, charybdotoxin and iberiotoxin, a blocker of small conduntance $Ca^{2+}$-activated $K^+$ channels, apamin and a blocker of ATP-sensitive $K^+$ channels, glibenclamide had no effect on the NANC relaxations, respectively. Exogeneous administration of nitric oxide (NO, 1~30${\mu}M$) caused concentration-dependent relaxations which showed a similarity to those obtained with EFS. None of the $K^+$ channel blockers had an effect on the concentration-dependent relaxation in response to NO. These results suggest that prejunctional $K^+$ channels regulate the release of NO from the NANC nerve in the rabbit proximal stomach as the inhibition of prejunctional $K^+$ channels increases the NANC relaxation induced by the EFS.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.4
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• pp.131-135
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• 2008

The profile of membrane currents was investigated in differentiated neuronal cells derived from human neural stem cells (hNSCs) that were obtained from aborted fetal cortex. Whole-cell voltage clamp recording revealed at least 4 different currents: a tetrodotoxin (TTX)-sensitive $Na^+$ current, a hyperpolarization-activated inward current, and A-type and delayed rectifier-type $K^+$ outward currents. Both types of $K^+$ outward currents were blocked by either 5 mM tetraethylammonium (TEA) or 5 mM 4-aminopyridine (4-AP). The hyperpolarization-activated current resembled the classical $K^+$ inward current in that it exhibited a voltage-dependent block in the presence of external $Ba^{2+}$ (30 ${\mu}$M) or $Cs^+$ (3${\mu}$M). However, the reversal potentials did not match well with the predicted $K^+$ equilibrium potentials, suggesting that it was not a classical $K^+$ inward rectifier current. The other $Na^+$ inward current resembled the classical $Na^+$ current observed in pharmacological studies. The expression of these channels may contribute to generation and repolarization of action potential and might be regarded as functional markers for hNSCs-derived neurons.