• The Korean Journal of Physiology and Pharmacology
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• 제3권5호
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• pp.471-479
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• 1999

The Kv channel activity in vascular smooth muscle cell plays an important role in the regulation of membrane potential and blood vessel tone. It was postulated that increased blood vessel tone in hypertension was associated with alteration of Kv channel and membrane potential. Therefore, using whole cell mode of patch-clamp technique, the membrane potential and the 4-AP-sensitive Kv current in cerebral arterial smooth muscle cells were compared between normotensive rat and one-kidney, one-clip Goldblatt hypertensive rat (lK,lC-GBH rat). Cell capacitance of hypertensive rat was similar to that of normotensive rat. Cell capacitance of normotensive rat and 1K,lC-GBH rat were $20.8{\pm}2.3$ and $19.5{\pm}1.4$ pF, respectively. The resting membrane potentials measured in current clamp mode from normotensive rat and 1K,lC-GBH rat were $-45.9{\pm}1.7$ and $-38.5{\pm}1.6$ mV, respectively. 4-AP (5 mM) caused the resting membrane potential hypopolarize but charybdotoxin $(0.1\;{\mu}M)$ did not cause any change of membrane potential. Component of 4-AP-sensitive Kv current was smaller in 1K,lC-GBH rat than in normotensive rat. The voltage dependence of steady-state activation and inactivation of Kv channel determined by using double-pulse protocol showed no significant difference. These results suggest that 4-AP-sensitive Kv channels playa major role in the regulation of membrane potential in cerebral arterial smooth muscle cells and alterations of 4-AP-sensitive Kv channels would contribute to hypopolarization of membrane potential in 1K,lC-GBH rat.

• The Korean Journal of Physiology and Pharmacology
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• 제3권6호
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• pp.547-554
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• 1999

The aim of the present study is to investigate the contribution of $Ca^{2+} ?activated\;K^+\;(K_{Ca})$ channels and delayed rectifier $K^+\;(K_V)$ channels to the resting membrane potential (RMP) in rabbit middle cerebral arterial smooth muscle cells. The RMP and membrane currents were recorded using the whole-cell patch configuration and single $K_{Ca}$ channel was recorded using the outside-out patch configuration. Using the pipette solution containing 0.05 mM EGTA, the RMP was $-25.76{\pm}5.08$ mV (n=12) and showed spontaneous transient hyperpolarizations (STHPs). The membrane currents showed time- and voltage-dependent outward currents with spontaneous transient outward currents (STOCs). When we recorded the membrane potential using the pipette solution containing 10 mM EGTA, the RMP was depolarized and did not show STHPs. The membrane currents showed no STOCs but only showed slowly inactivating outward currents. External TEA (1 mM) reversibly inhibited the STHPs, depolarized the RMP, reduced the membrane currents, abolished STOCs, and decreased the open probability of single $K_{Ca}$ channel. When $K_V$ currents were isolated, the application of 4-AP (5 mM) depolarized the RMP. The important aspect of our results is that $K_{Ca}$ channel is responsible for the generation of the STHPs in the membrane potential and plays an important role in the regulation of the RMP and $K_V$ channel is also responsible for the regulation of the RMP in rabbit middle cerebral arterial smooth muscle cells.

• The Korean Journal of Physiology and Pharmacology
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• 제4권4호
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• pp.301-309
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• 2000

The purpose of our investigation was to examine the effects of prostaglandin $F_{2{\alpha}}\;(PGF_{2{\alpha}})$ on membrane potentials, $Ca^{2+}-activated\;K^+\;(K_{Ca})$ channels, and delayed rectifier $K^+(K_V)$ channels using the patch-clamp technique in single rabbit middle cerebral arterial smooth muscle cells. $PGF_{2{\alpha}}$ significantly hyperpolarized membrane potentials and increased outward whole-cell K currents. $PGF_{2{\alpha}}$ increased open-state probability of $K_{Ca}$ channels without the change of the open and closed kinetics. $PGF_{2{\alpha}}$ increased the amplitudes of $K_V$ currents with a leftward shift of activation and inactivation curves and a decrease of activation time constant. Our results suggest that the activation of $K_{Ca}$ and $K_V$ channels, at least in part, may lead to attenuate or counteract vasoconstriction by $PGF_{2{\alpha}}$ in middle cerebral artery.

• 대한한의학회지
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• 제20권2호
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• pp.146-156
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• 1999

The present study was performed to investigate the effect of Yangkyuksanhoa-tang on the morphological changes of the basilar artery after experimentally induced subarachnoid hemonrrhages(SAH). Yangkyuksanhoa-tang has been used freguently for cerebrovascular accident Sprague Dawley rats weighing between 350-400 g were used. The 6 normal rats and 24 SAH elicited rats were used, The SAH induced by injection of the fresh autologus heart blood (0.3-0.4 ml) into the cisterna magna through the posterior atlanta-occipital membrane, Sample group was given 3.3 ml/kg/day of Yangkyuksanhoa-tang extracts for 2 days after SAH. The experimental animals were killed at 48hrs after SAH. The morphological changes of the arterial walls were examined by light and electron microscopy. Following are the obtained results: 1. In SAH elicited rats, the size of the lumen in basilar artery was diminished by about 45% and the thickness of arterial wall was increased by about 82%. In SAH elicited rats with Yangkyuksanhoa-tang treatment, the size of the lumen in basilar artery was merely diminished by about 18% and the thickness of arterial wall was merely increased by about 19%. 2. In light microscopic examination, the endothelium was swollen into a cuboid shape and the layer of smooth muscle was increased in the basilar artery of SAH elicited rats. In SAH elicited rats with Yangkyuksanhoa-tang treatment, the size of the lumen in basilar artery was enlarged and the thickness was decreased than in SAH elicited rats. The endothelium was flattened into a squamous shape and the layer of smooth muscle was decreased more than in SAH elicited rats. 3. In electron microscopic examination, the endothelial cells with fragmentation nuclei were changed into a cuboid shape and the internal elastic lamina were folded at the basilar artery of SAH elicited rat. The nuclei of smooth muscle cells were changed into a round or crumpled shape. The length of smooth muscle was shorten and thickness was increased. But all kinds of morphologic changes were diminished in SAH elicited rats with Yangkyuksanhoa-tang treatment. Conclusion : Yangkyuksanhoa-tang extracts were effective to treat cerebral vasospasm after experimentally induced subarachnoid hemorrhage in rats.

• The Korean Journal of Physiology and Pharmacology
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• 제4권6호
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• pp.445-453
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• 2000

The present investigation tested the hypothesis that the activation of protein kinase G (PKG) leads to a phosphorylation of $Ca^{2+}-activated$ potassium channel $(K_{Ca}\;channel)$ and is involved in the activation of $K_{Ca}$ channel activity in cerebral arterial smooth muscle cells of the rabbit. Single-channel currents were recorded in cell-attached and inside-out patch configurations of patch-clamp techniques. Both molsidomine derivative 3-morpholinosydnonimine-N-ethylcarbamide $(SIN-1,\;50\;{\mu}M)$ and 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate $(8-pCPT-cGMP,\;100\;{\mu}M),$ a membrane-permeable analogue of cGMP, increased the $K_{Ca}$ channel activity in the cell-attached patch configuration, and the effect was removed upon washout of the drugs. In inside-out patches, single-channel current amplitude was not changed by SIN-1 and 8-pCPT-cGMP. Application of ATP $(100\;{\mu}M),$ cGMP $(100\;{\mu}M),$ ATP+cGMP $(100\;{\mu}M\;each),$ PKG $(5\;U/{\mu}l),$ ATP $(100\;{\mu}M)+PKG\;(5\;U/{\mu}l),$ or cGMP $(100\;{\mu}M)+PKG\;(5\;U/{\mu}l)$ did not increase the channel activity. ATP $(100\;{\mu}M)+cGMP\;(100\;{\mu}M)+PKG\;(5\;U/{\mu}l)$ added directly to the intracellular phase of inside-out patches increased the channel activity with no changes in the conductance. The heat-inactivated PKG had no effect on the channel activity, and the effect of PKG was inhibited by 8-(4-Chlorophenylthio)-guanosine-3',5'-cyclic monophosphate, Rp-isomer $(Rp-pCPT-cGMP,\;100\;{\mu}M),$ a potent inhibitor of PKG or protein phosphatase 2A (PP2A, 1 U/ml). In the presence of okadaic acid (OA, 5 nM), PP2A had no effect on the channel activity. The $K_{Ca}$ channel activity spontaneously decayed to the control level upon washout of ATP, cGMP and PKG, and this was prevented by OA (5 nM) in the medium. These results suggest that the PKG-mediated phosphorylations of $K_{Ca}$ channels, or some associated proteins in the membrane patch increase the activity of the $K_{Ca}$ channel, and the activation may be associated with the vasodilating action.

• 대한약리학회지
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• 제26권1호
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• pp.25-33
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• 1990

가토의 적출동맥평활근 절편에 대한 peptide YY(PYY)의 수축작용을 관찰하고, PYY의 수축기전상 동원되는 칼슘의 기원을 조사하여 다음과 같은 결과를 얻었다. 각 동맥의 나선형 절편은 PYY의 실험조내 첨가에 의하여 농도의존적인 수축반응을 보였다. 그중 대퇴동맥이 가장 강력하고 예민한 수축경향을 보였으며, 그 다음은 대뇌의 기저동맥, 총장골동맥, 상장간막동맥, 신동맥, 총경동맥의 순으로 예민하였다. PYY에 대한 반응성을 Norepinephrine(NE)에 대한 반응성과 비교해볼때, 총경동맥과 신동맥은 PYY보다 NE에 대해서 유의하게 $(p{\leqslant}0.05)$예민하였고, 기저동맥은 NE보다 PYY에 더 예민하였다$(p{\leqslant}0.05)$. 대퇴동맥 절편에서 칼슘통로봉쇄제인 verapamil과 세포내 저장칼슘유리를 억제하는 3,4,5-Trimethoxybenzoic acid 8-(diethylamino)octyl ester ${\ulcorner}TMB-8{\lrcorner}$는 각각 PYY에 의한 수축을 억제하였는데 $(p{\leqslant}0.05)$, verapamil과 TMB-8이 동시에 존재할 때는 PYY에 의한 수축은 거의 완전히 억제되었고, ethyleneglycol-bis-(beta-aminoethyl ether), N,N,N‘,N’-tetraacetic acid${\ulcorner}EGTA{\lrcorner}$0.5mM를 첨가한 칼슘배제용액 내에서도 PYY에 의한 수축은 거의 완전히 억압되었다. 이상의 결과를 종합하면, 혈중 PYY가 증가했을 때는 교감신경계흥분시보다 강한 뇌혈관의 수축이 일어날 수 있으며, 뇌동맥압은 교감신경계 흥분시보다 더 높을 수가 있으리라 추정된다. 또 PYY에 의한 혈관 평활근 수축에는 세포외액의 칼슘과 세포내저장칼슘의 이용이 공히 필수적이라고 생각된다.

• The Korean Journal of Physiology and Pharmacology
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• 제3권1호
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• pp.1-10
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• 1999

We sought to find out the mechanism of vascular relaxation by extracellular $K^+$ concentration $([K^+]_o)$ in the cerebral resistant arteriole from rabbit. Single cells were isolated from the cerebral resistant arteriole, and using voltage-clamp technique barium-sensitive $K^+$ currents were recorded, and their characteristics were observed. Afterwards, the changes in membrane potential and currents through the membrane caused by the change in $[K^+]_o$ was observed. In the smooth muscle cells of cerebral resistant arteriole, ion currents that are blocked by barium, 4-aminopyridine (4-AP), and tetraethylammonium (TEA) exist. Currents that were blocked by barium showed inward rectification. When the $[K^+]_o$ were 6, 20, 60, and 140 mM, the reversal potentials were $-82.7{\pm}1.0,\;-49.5{\pm}1.86,\;-26{\pm}1.14,\;-5.18{\pm}1.17$ mV, respectively, and these values were almost identical to the calculated $K^+$ equilibrium potential. The inhibition of barium-sensitive inward currents by barium depended on the membrane potential. At the membrane potentials of -140, -100, and -60 mV, $K_d$ values were 0.44, 1.19, and 4.82 ${\mu}M,$ respectively. When $[K^+]_o$ was elevatedfrom 6 mM to 15 mM, membrane potential hyperpolarized to -50 mV from -40 mV. Hyperpolarization by $K^+$ was inhibited by barium but not by ouabain. When the membrane potential was held at resting membrane potential and the $[K^+]_o$ was elevated from 6 mM to 15 mM, outward currents increased; when elevated to 25 mM, inward currents increased. Fixing the membrane potential at resting membrane potential and comparing the barium-sensitive outward currents at $[K^+]_o$ of 6 and 15 mM showed that the barium- sensitive outward current increased at 15 mM $K^+.$ From the above results the following were concluded. Barium-sensitive $K^+$?channel activity increased when $[K^+]_o$ is elevated and this leads to an increase in $K^+-outward$ current. Consequently, the membrane potential hyperpolarizes, leading to the relaxation of resistant arteries, and this is thought to contribute to an increase in the local blood flow of brain.