• The Korean Journal of Physiology and Pharmacology
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• 제1권6호
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• pp.783-796
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• 1997

The relaxation induced by stimulation of the inhibitory non-adrenergic, non-cholinergic (iNANC) nerve is mediated by the release of iNANC neurotransmitters such as nitric oxide (NO), vasoactive intestinal peptide (VIP) and adenosine triphosphate (ATP). The mechanisms of NO, VIP or ATP-induced relaxation have been partly determined in previous studies, but the detailed mechanism remains unknown. We tried to identify the nature of iNANC neurotransmitters in the smooth muscle of guinea pig ileum and to determine the mechanism of the inhibitory effect of nitric oxide. We measured the effect of NO-donors VIP and ATP on the intracellular $Ca^{2+}$ concentration$([Ca^{2+}]_i)$, by means of a fluorescence dye(fura 2) and tension simultaneously in the isolated guinea pig ileal smooth muscle. Following are the results obtained. 1. Sodium nitroprusside $(SNP:10^{-5}\;M)$ or S -nitro-N-acetyl-penicillamine $(SNP:10^{-5}\;M)$ decreased resting $[Ca^{2+}]_i$ I and tension of muscle. SNP or SNAP also inhibited rhythmic oscillation of $[Ca^{2+}]_i$ and tension. In 40mM $K^+$ solution or carbachol ($(CCh:10^{-6}\;M)$-induced precontracted muscle, SNP decreased muscle tension. VIP did not change $[Ca^{2+}]_i$ and tension in the resting or precontracted muscle, but ATP increased resting $[Ca^{2+}]_i$ and tension in the resting muscle. 2. 1H-[1,2,4]oxadiazol(4,3-a)quinoxalin-1-one $(ODQ:1\;{\mu}M)$, a specific inhibitor of soluble guanylate cyclase, limited the inhibitory effect of SNP 3. Glibenclamide $(10\;{\mu}M)$, a blocker of $K_{ATP}$ channel, and 4-aminopyridine (4-AP:5 mM), a blocker of delayed rectifier K channel, apamin $(0.1\;{\mu}M)$, a blocker of small conductance $K_{Ca}$ channel had no effect on the inhibitory effect of SNP. Iberiotoxin $(0.1\;{\mu}M)$, a blocker of large conductance $K_{Ca}$ channel, significantly increased the resting $[Ca^{2+}]_i$, and tension, and limited the inhibitory effect of SNP. 4. Nifedipine $(1\;{\mu}M)$ or elimination of external $Ca^{2+}$ decreased not only resting $[Ca^{2+}]_i$ and tension but also oscillation of $[Ca^{2+}]_i$ and tension. Ryanodine $(5\;{\mu}M)$ and cyclopiazonic acid $(10\;{\mu}M)$ decreased oscillation of $[Ca^{2+}]_i$ and tension. 5. SNP decreased $Ca^{2+}$ sensitivity of contractile protein. In conclusion, these results suggest that 1) NO is an inhibitory neurotransmitter in the guinea pig ileum, 2) the inhibitory effect of SNP on the $[Ca^{2+}]_i$ and tension of the muscle is due to a decrease in $[Ca^{2+}]_i$ by activation of the large conductance $K_{Ca}$ channel and a decrease in the sensitivity of contractile elements to $Ca^{2+}$ through activation of G-kinase.

• Journal of Ginseng Research
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• 제23권4호
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• pp.230-234
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• 1999

혈관의 평활근 세포막에 존재하는 포타슘채널은 근세포의 막전압을 조절하여 근수축 및 이완을 조절한다. 네가지 유형의 포타슘채널이 근세포막에 존재하며 이중 전도도가 큰 칼슘의존성-포타슘채널$(BK_{Ca})$은 평활근 막전압 조절에 중요한 기능을 담당하는 채널로 알려져 있다. 현재 홍삼 복합사포닌이 혈관 평활근의 이완을 증진시켜 혈압강하를 촉진시킨다고는 알려져 있으나 어떤 분자적 기전이나 전기생리학 기전으로 작용하는지 정확히 알려져 있지 않다. 본 연구는 홍삼 복합사포닌 및 사포닌 $Rg_3$ 성분이 토끼 관상동맥 평활근 세포의 $BK_{Ca}$채널의 활성을 증진시켜 막전압을 과분극시키고 곧 평활근 이완을 촉진한다는 가설을 테스트하였다. 관상동맥 평활근세포의 $BK_{Ca}$채널은 막전압 의존성, 외향정류(outward rectification) 특성을 보였고 단일채널의 전도도는 200pS으로 측정되었으며 charybdotoxin 및 tetraethylammonium에 억제되는 약리학적 특성을 보였다 Whole-cell $BK_{Ca}$활성은 홍삼 복합사포닌에 의해서 농도 의존적으로 증가되었으나 막전압 의존성은 변화되지 않았으며, 단일채널이 열리는 시간은 증가되었다. 홍삼 사포닌 $Rg_3$성분도 막전압 의존성에는 영향을 주지 않으면서$BK_{Ca}$의 활성을 증가시켰으며 단일채널이 열리는 시간도 증가시켰다. 따라서 홍삼 복합사포닌 및 사포닌 $Rg_3$성분은 $BK_{Ca}$의 활성을 증가시켜 막전압을 과분극시켜 평활관의 이완을 촉진한다고 여겨진다.

• 대한수의학회지
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• 제35권2호
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• pp.245-254
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• 1995

The density of ATP-sensitive potassium($K_{APT}$) channels, that open as intracellular ATP concentration falls below a critical level, is very high in skeletal muscle surface membrane and those high density may imply that $K_{ATP}$ channels have very important physiological roles. To elucidate a role of $K_{ATP}$ in relation to fatigue, the modulating effects of potassium channel openers and blockers on the fatigue velocity(FV) of mouse extensor hallucis longus muscle(EHL) were investigated in vitro. Twitch contraction was induced by an electrical field stimulation (EFS: 24-48V, 20ms, 0.2-4Hz) and resulting contraction force was isometrically recorded. The twitch forces were gradually decreased to 25% of initial contraction force(ICF) in $37.52{\pm}1.55sec$($mean{\pm}s.e.m.$, n=135), indicating the fatigue phenomena. The mean velocity for development of the fatigue was measured during the period that twitch force decreased to half($FV_{0/0.5}$) and during the period from half to 25%($FV_{0.5/0.25}$) of ICF. The fatigue was induced once every one hour and the tissue response was stable for up to 4 hours. In control condition, ICF was $5.8{\pm}0.12g$ (n=144) and decreased to 50% of ICF with the mean fatigue velocity of $0.182{\pm}0.006g/sec$($FV_{0/0.5}$, n=135) and from 50% to 25% of ICF with $0.084{\pm}0.004g/sec$($FV_{0.5/0.25}$, n=135). Cromakalim($50{\mu}M$) significantly increased $FV_{0.5/0.25}$(n=4). Glibenclamide($IC_{50}>50{\mu}M$), $Ba^{2+}$($IC_{50}=10{\mu}M$), 4-aminopyridine($FV_{0/0.5}$, $IC_{50}=0.5mM$; $FV_{0.5/0.25}$, $IC_{50}=2mM$) decreased both $FV_{0/0.5}$ and $FV_{0.5/0.25}$ concentration-dependently up to 75%. $TEA^+$(30mM), E-4031($10{\mu}M$), tolbutamide(1mM) decreased $FV_{0.5/0.25}$, but apamin(300nM) and $TEA^+$(10mM) showed no significant effects. Our results suggest that activation of the $K_{ATP}$ channels may be major cause of $K^+$ outflux during development of the fatigue and the isolated EHL muscle could be an useful experimental preparation in studying the fatigue phenomena in skeletal muscle. In addition, the possibility of activation of delayed rectifier during the fatigue development remains to be studied further.

• International Journal of Oral Biology
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• 제38권1호
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• pp.13-19
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• 2013

Various voltage-gated $K^+$ currents were recently described in dorsal root ganglion (DRG) neurons. However, the characterization and diversity of voltage-gated $K^+$ currents have not been well studied in trigeminal root ganglion (TRG) neurons, which are similar to the DRG neurons in terms of physiological roles and anatomy. This study was aimed to investigate the characteristics and diversity of voltage-gated $K^+$ currents in acutely isolated TRG neurons of rat using whole cell patch clamp techniques. The first type (type I) had a rapid, transient outward current ($I_A$) with the largest current size having a slow inactivation rate and a sustained delayed rectifier outward current ($I_K$) that was small in size having a fast inactivation rate. The $I_A$ currents of this type were mostly blocked by TEA and 4-AP, K channel blockers whereas the $I_K$ current was inhibited by TEA but not by 4-AP. The second type had a large $I_A$ current with a slow inactivation rate and a medium size-sustained delayed $I_K$ current with a slow inactivation rate. In this second type (type II), the sensitivities of the $I_A$ or $I_K$ current by TEA and 4-AP were similar to those of the type I. The third type (type III) had a medium sized $I_A$ current with a fast inactivation rate and a large sustained $I_K$ current with the slow inactivation rate. In type III current, TEA decreased both $I_A$ and $I_K$ but 4-AP only blocked $I_A$ current. The fourth type (type IV) had a smallest $I_A$ with a fast inactivation rate and a large $I_K$ current with a slow inactivation rate. TEA or 4-AP similarly decreased the $I_A$ but the $I_K$ was only blocked by 4-AP. These findings suggest that at least four different voltage-gated $K^+$ currents in biophysical and pharmacological properties exist in the TRG neurons of rats.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1996년도 춘계학술대회
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• pp.175-175
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• 1996

The spinal dorsal horn is the area where primary afferent fibers terminate and cutaneous sensory information is Processed. A number of putative neurotransmitter substances, including excitatory and inhibitory amino acids and peptides, are present in this region and sites and cellular mechanisms of their actions have been a target of numerous studies. In this study, single neurons were acutely isolated and the properties of whole cell current and responses to excitatory and inhibitory neurotransmitters were studied by the patch clamp method. Young rats (7-14 days) were anesthetized with diethyl-ether, and the lumbar spinal cord was excised and cut transversely at a thickness of 30$\mu\textrm{m}$ by Vibroslicer. The treatment of spinal slices with low concentration of proteases (pronase and thermolysin 0.75 mg/$m\ell$) and mechanical dissociation yielded isolated neurons with near intact morphology. Multipolar, ellipsoidal and bipolar, and pyramidal cells were shown. By applying step voltage pulses to neurons held at -70 mV, two types of inward currents and one outward currents observed. The fast activating and inactivating inward current was the Na$\^$+/ current because of its fast kinetics and blocking by 0.5${\mu}$M TTX, a specific blocker of Na$\^$+/ channel. The second type of inward currents were sustained. Based on their kinetics and current-voltage relations, it was likely that the second type of inward current was the voltage-dependent Ca$\^$2+/ current. In the presence of TTX, the steady-state currents mainly represented outward K$\^$+/ current which looked like the delayed rectifier K$\^$+/ current. In addition, the membrane currents produced by agonist of excitatory amino acid (EAA) receptor and the endogenous transmitter candidate L-glutamate were recorded in isolated whole-cell voltage clamped neurons as well as responses to inhibitory amino acids (${\gamma}$-amino butyric acid, glycine). Drugs were applied by a method that allows complete exchange of the solution within 1 sec; an infinite number of solutions can be applied to a single cell.

• 대한약리학회지
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• 제32권1호
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• pp.1-11
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• 1996

흰쥐 해마(hippocampus)에서 norepinephrine(NE) 유리에 미치는 $A_1-adenosine$ 수용체의 post-receptor 기전에 관한 지견을 얻고자 하여 $^3H-norepinephrine$으로 평형시킨 해마 절편을 사용하여 adenosine의 $^3H-NE$ 유리에 미치는 여러가지 약물의 영향을 관찰하였다. Adenosine($1{\sim}30{\mu}M$)은 전기자극(3 Hz, 2 ms, 5 Vcm-1, 구형파)에 의한 NE 유리를 용량 의존적으로 감소시켰고, 이 효과는 선택적인 $A_1-adenosine$ 수용체 차단제인 $8-cyclopentyl-1,3-dipropylxanthine(2{\mu}M)$에 의해 차단되었다. G-단백 억제제인 N-ethylmaleimide(NEM, 10과 $30{\mu}M$)는 그 자체로써 전기자극으로 유발시킨 NE 유리를 증가시켰으며, adenosine의 NE 유리 억제효과는 NEM 전처리에 의하여 완전히 소실되었다. Protein kinase C 활성화제인 $4{\beta}-phorbol$ 12,13-dibutyrate(PDB, $1{\mu}M$)는 NE 유리 증가를 일으켰고, 이 효소 억제제인 $4{\beta}-polymyxin$ B(PMB, 0.1 mg)는 NE 유리감소를 일으켰으며, adenosine에 의한 NE 유리 감소효과는 PDB에 의해 억제되었고, PMB 전처리하에서는 감소효과가 출현하지 않았다. $Ca^{2+}$-통로 차단제인 $nifedipine(1{\mu}M$)은 adenosine의 NE 유리 억제효과에 영향을 미치지 못하고, ATP에 의존적인 $K^+-$통로 차단제인 glibenclamide역시 adenosine의 NE 유리 억제효과에 영향을 미치지 못하였다. 그러나 delayed rectifier $K^+-$통로 차단제인 tetraethylammonium(TEA, 3 mM)은 그 자체로 NE 유리를 증가 시켰으며, adenosine의 NE 유리 억제효과를 차단함을 볼 수 있었다. 8-bromo-cAMP(100과 $300{\mu}M$) 그 자체로는 NE 유리에 별다른 영향을 미치지 못하였으나 8-bromo-cAMP 전처리에 의하여 adenosine의 NE 유리 억제효과가 억제됨을 볼 수 있었다. 이상의 실험결과로 흰쥐 해마에서 $A_1-adenosine$ 수용체를 통한 adenosine의 NE 유리 감소는 G-단백에 의존적이며, 이러한 효과에 protein kinase C, TEA에 예민한 $K^+-$통로 및 adenylate cyclase계가 복합적으로 관여하고 nifedipine에 예민한 $Ca^{2+}-$통로와 glibenclamide에 예민한 $K^+-$통로는 관여하지 않는 것으로 사료된다.