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JYMS : Journal of Yeungnam Medical Science

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Oh Cheol Kwon 7 Articles
Effects of octreotide on the contractility of isolated rat vas deferens.
Sun Ae Jang, Oh Cheol Kwon, Jeoung Hee Ha, Kwang Youn Lee, Won Joon Kim
Yeungnam Univ J Med. 1993;10(1):144-156.   Published online June 30, 1993
DOI: https://doi.org/10.12701/yujm.1993.10.1.144
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This study was performed to investigate the effect of octreotide on the contractility of rat vas deferens. The -smooth muscle strips isolated from the prostatic portion were myographied in isolated organ bath. Electric -field stimulation (monophasic square wave, duration : 1. mSec, voltage : 50 V, frequency : 5 Hz or 30 Hz, train : 10 Sec) produced reproducible contraction. The contraction was composed of two component, first phasic component (FPC) and second tonicc component (STC).. These contractions were abolished by -tetrodotoxin (1 microM). Octreotide inhibited the field stimulation induced contractions both FPC and STC concentration- dependently. The FPC was decreased by a desentization of purinergic receptor by pretreatment of mATP, and the STC was decreased by pr,,creatment of reserpine (3 mg/kg, EP) 24 hours before experiments. Octreotide reduced the field stimulation induced contraction in the presence of mATP and of reserpinized muscle strips. The inhibitory effect of octreotide was more potent at 5 Hz than at 30 Hz. Octreotide did not affect basal ton and exogenous norepinephrine- or ATP-induced contraction. These results suggest that octreotide inhibit the contractility of the isolated rat vas deferens by inhibition of the release of neurotransmitters, both ATP and norepinephrine from adrenergic nerve terminal.
Inhibitory of γ-aminobutyric acid on the contractility of isolated rat vas deferens.
Ki Young Ahn, Oh Cheol Kwon, Jeoung Hee Ha, Kwang Youn Lee, Won Joon Kim
Yeungnam Univ J Med. 1992;9(2):382-395.   Published online December 31, 1992
DOI: https://doi.org/10.12701/yujm.1992.9.2.382
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GABA is an inhibitory neurotransmitter in central nervous system and produce sedative, antianxiety and muscle relaxing effects via GABA(A) receptor or GABA(B) receptor. Recently it is known that GABA is widely distributed throughout peripheral organs and may play a physiological role in certain organ. The vas deferens is innervated by species-difference. These study, therefore, was performed to investigate the mode and the mechanism of action of GABA on the norepinephrine-, ATP- and electric stimulation-induced contraction of vas deferens of rat. Sprague-Dawley rats were sacrificed by cervical dislocation. The smooth muscle strips were isolated from the prostatic portion and were mounted in the isolated muscle bath. PSS in the bath was aerated with 95/5%-O₂/CO₂ at 33℃. Muscle tensions were measured by isometric tension transducer and were recorded by biological recording system. 1. GABA, muscimol, a GABA(A) agonist, and baclofen, a GABA(B) agonist inhibited the electric field stimulation (EFS, 0.2Hz, 1mSec, 80V, monophasic square wave)-induced contraction with a rank order of potency of GABA greater than baclofen greater than muscimol. 2. The inhibitory effect of GABA was antagonized by delta aminovaleric acid (DAVA), a GABA(B) antagonist, but not by bicuculline, a GABA(A) intagonist. 3. The inhibitory effect of baclofen was antagonized by DAVA, but the effect of muscimol was not antagonized by bicuculline. 4. Exogenous norepinephrine (NE) and ATP contracted muscle strip concentration dependently, but the effect of acetylcholine was negligible and GABA did not affect the NE-and ATP-induced contractions. 5. GABA, baclofen and muscimol did not affect basal tone, and GABA did not affect the NE-and ATP-induced contractions. 6. EFS-induced contraction was inclucling 2 distinctable components. The first phasic component was inhibited by beta gamma-methylene ATP (mATP), a desensitizing agent of APT receptor and the second tonic component was reduced by pretreatment of reserpine (3 mg/Kg, IP). 7. GABA inhibited the EFS-induced contraction of reserpinized strips, but not the mATP-treated strips. These results suggest that in the prostatic portion of the rat vas deferens, adrenergic and purinergic neurotransmissions are exist, and GABA inhibits the release of ATP via presynaptic GABA(B) receptor on the excitatory neurons.
Effect of diazepam on the oxytocin induced contraction of the isolated rat uterus.
Yoon Kee Park, Sung Ho Lee, Oh Cheol Kwon, Jeoung Hee Ha, Kwang Youn Lee, Won Joon Kim
Yeungnam Univ J Med. 1992;9(2):359-381.   Published online December 31, 1992
DOI: https://doi.org/10.12701/yujm.1992.9.2.359
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This study was designed to investigate the effect of diazepam on the spontaneous contraction and oxytocin induced contraction of the isolated rat uterus. Female rat (Sprague-Dawley) pretreated with oophorectomy and 4 days administration of estrogen. Weighing about 200 g, was sacrificed by cervical dislocation, and the uteruses were isolated. A longitudinal muscle strip was placed in temperature controlled (37℃) muscle chamber containing Locke's solution and myographied isometrically. Diazepam inhibited the spontaneous contraction and oxytocin induced contraction of the isolated rat uterus in a concentration-dependent manner. GABA, muscimol, a GABA A receptor agonist, bicuculline, a competitive GABA A receptor antagonist, picrotoxin, a non competitive GABA A receptor antagonist, baclofen, a GABA B receptor agonist, and delta-aminovaleric acid, a GABA B receptor antagonist, did not affect on the spontaneous and oxytocin induced contraction of the isolated rat uterus. The inhibitory actions of diazepam on the spontaneous and oxytocin induced contraction were not affected by all the GABA receptor agonists and antagonists, but exceptionally potentiated by bicuculline. This potentiation-effect by bicuculline was not antagonized by muscumol. In normal calcium PSS, addition of calcium restored the spontaneous contraction preinhibited by diazepam and recovered the contractile of oxtrocin preinhibited by diazepam. A23187, a calcium inophore, enhanced the restoration of both the spontaneous and oxytocin induced contraction by addition of calcium. In calcium-free PSS, diazepam suppressed the restoration of spontaneous motility by addition of calcium but allowed the recovery of spontaneous motility to a considerable extent. Diazepam could not inhibit some development of contractility by oxytocin in calcium-free PSS, but inhibited the increase in contractility by subsequent addition of calcium. These results suggest that the inhibitory action of diazepam on the rat uterine motility does not depend on or related to GABA receptors and that diazepam inhibits the extracellular calcium influx to suppress the spontaneous and oxytocin induced contractilities.
Existance of cholinergic and purinergic receptor on the detrusor muscle of rat urinary bladder.
Tae Su Choi, Oh Cheol Kwon, Jeoung Hee Ha, Kwang Youn Lee, Won Joon Kim
Yeungnam Univ J Med. 1991;8(2):138-149.   Published online December 31, 1991
DOI: https://doi.org/10.12701/yujm.1991.8.2.138
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This study was aimed at investigation of the stimulatory innervations on the rat urinary bladder. Detrusor muscle strips of 15 mm long were suspended in isolated muscle chambers containing 1 ml of PSS maintained at 37℃ and aerated with 95% O²/5% Co². Isometric myography was performed, and the results were as followings: Muscle strips showed “on-contraction” by electric field stimulation (EFS) frequency-dependently. The EFS-induced contraction was not affected by hexamethonium, a ganglion blocker, but abolished by tetrodotoxin, a nerve conduction blocker. Physostigmine, a cholinesterase inhibitor enhanced the EFS-induced contraction which was inhibited by hemicholinium, an inhibitor of choline uptake at the cholinergic nerve ending. Such an EFS-induced contraction was antagonized by atropine only partially, and the atropine-resistant portion was completely abolished by the desensitization of purinergic receptors by prolonged incubating of the strips in the presence of high concentration of ATP. Bethanechol, a cholinergic agonist, elicited concentration-dependent contraction. Adenosine triphosphate (ATP), a purinergic agonist, induced a weak but concentration-dependent contraction of short duration. Bethanechol-induced contraction was not affected by ATP-desensitization, and ATP-induced contraction was not affected by tetrodotoxin. These results suggest that there are at least two main stimulatory components of innervations in the detrusor muscle, cholinergic muscarinic and purinergic; and those receptors are independent each other.
Effect of GABA on the contratility of small intestine isolated from rat.
Joon Young Huh, Oh Cheol Kwon, Jeoung Hee Ha, Kwang Youn Lee, Won Joon Kim
Yeungnam Univ J Med. 1991;8(2):95-105.   Published online December 31, 1991
DOI: https://doi.org/10.12701/yujm.1991.8.2.95
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This study was designed to investigate the effect of GABA and related substances on the spontaneous contraction of rat small intestine. The rats (Sprague-Dawley), weighing 200-250g, were sacrificed by cervical dislocation, and the small intestine was isolated. Longitudinal muscle strips from duodenum, jejunum and ileum were suspended in Biancani's isolated muscle chambers and myographied isometrically. GABA and muscimol, a GABA A receptor agonist relaxed the duodenum and jejunum significantly, but baclofen-induced relaxation in those muscle strips negligible. The effectiveness of GABA and muscimol in various regions were the greatest on duodenum, and greater on jejunum than on ileum The effect of GABA and muscimol was antagonized by bicuculline, a competitive GABA A receptor antagonist and picrotoxin, a noncompetitive GABA A receptor antagonist. Duodenal relaxation induced by GABA and muscimol was unaffected by hexamethonium, but was prevented by tetrodotoxin. These results suggest that GABA inhibit the contractility of smooth muscle with distinct regional difference of efficacy, and the site of inhibitory action is the GABA A receptor existing at the presynaptic membrane of postganglionic excitatory nerves.
The Effects of Diazepam on the Carbachol Induced Contraction of the Isolated Rat Ileum.
Jung Ok Kim, Oh Cheol Kwon, Jeoung Hee Ha, Kwang Youn Lee, Won Joon Kim
Yeungnam Univ J Med. 1989;6(2):13-22.   Published online December 31, 1989
DOI: https://doi.org/10.12701/yujm.1989.6.2.13
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To investigate the effect of diazepam on the contractility of the intestinal smooth muscle, longitudinal muscle strip isolated from rat ileum was prepared for myography in isolated organ bath. 1) Basal tone of ileal muscle was reduced by diazepam concentration-dependently. 2) Higher concentrations (30 and 100 microM) of diazepam inhibited (p<0.05, p<0.001) The carbachol-induced contraction in a concentration-dependent manner; but lower concentration of diazepam (10 microM) enhanced (p<0.05). 3) Histamine-induced contraction was inhibited by pretreatment with diazepam in a concentration-dependent manner. 4) Ca⁺⁺-induced tension recovery in calcium-free solution was inhibited in the presence of diazepam concentration-dependently. These results suggest diazepam reduces the contractility of the longitudinal muscle isolated from rat ileum via interference with influx of calcium into the muscle cells.
Effects of Strontium on Norepinephrine Induced Positive Inotropic Effect of Isolated Perfused Rat Hearts.
Oh Cheol Kwon, Kwang Youn Lee
Yeungnam Univ J Med. 1988;5(2):59-69.   Published online December 31, 1988
DOI: https://doi.org/10.12701/yujm.1988.5.2.59
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This study was designed to investigate the effect of substitution of strontium for calcium on mechanical activity in isolated perfused spontaneously beating rat hearts. The mechanical activity of the hearts of Langendorff's preparation in conditions of low calcium and strontium-substitution for calcium was compared. The effect of norepinephrine and verapamil were also observed in those conditions. The results were as follows: 1. In low calcium, the mechanical activity of the heart preparation was significantly reduced, but when the equimolar strontium was substituted for the reduced calcium, the activity was kept at similar level to the normal condition. 2. When equimolar strontium was substituted for the total calcium in perfusate, the heart preparation stopped its beating, and it was not restored in spite of reperfusion with normal calcium perfusate. 3. Norepinephrine-induced positive inotropic effect was inhibited in low-calcium condition especially with low concentration of norepinephrine, but not in strontium-substitution for calcium. 4. Verapamil reduced the activity of the heart both in low-calcium and strontium-substitution as well as in normal calcium conditions. From above results, it was concluded that strontium served as a substitute of calcium in maintaining mechanical activity and in responsiveness to norepinephrine, and the influx of strontium through cell membrane is inhibited by verapamil as the influx of calcium.

JYMS : Journal of Yeungnam Medical Science