• Title/Summary/Keyword: 가토

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Contractile Action of Barium in the Rabbit Renal Artery (가토 신동맥 평활근에서 Barium의 수축작용)

  • Jeon, Byeong-Hwa;Kim, Sahng-Seop;Kim, Se-Hoon;Chang, Seok-Jong
    • The Korean Journal of Physiology
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    • v.24 no.2
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    • pp.293-303
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    • 1990
  • The contractile action of barium $(Ba^{2+})$ was investigated in the arterial strip of rabbit renal artery. The helical strip of isolated renal artery was immersed in the Tris-buffered Tyrode's solution equilibrated with 100% $O_2$ at $37^{\circ}C$ and its isometric tension was measured. $Ba^{2+}-induced$ contraction of arterial strip was dose-dependent and its maximal tension corresponded to $92.1{\pm}4.5%$ of tension by $K^+(100\;mM)$. $Ba^{2+}-induced$ contraction did not show the tachyphylactic phenomenon in the normal Tyrode's solution. $Ba^{2+}$ induced the tonic contraction in the $Ca^{2+}-free$ tyrode's solution and that was increased by the extracellula addition of $Ca^{2+}$. During the repeated exposure of the same dose of $Ba^{2+}\;(10\;mM)$ in the $Ca^{2+}-free$ Tyrode's solution, $Ba^{2+}-induced$ contraction was progressively decreased. Even though the intracellular NE-and caffeine-sensitive $Ca^{2+}$ was depleted, $Ba^{2+}$ induced the tonic contraction. After the pretreatment of lanthnum or verapamil, $Ba^{2+}$ did not induce contraction. $Ba^{2+}-induced$contraction was suppressed by extracellular $K^+$ in the normal Tyrode's solution and that was dependent on $K^+$ concentration. Suppressive effect of $K^+\;(14\;mM)$ on the $Ba^{2+}-induced$ contraction was also dependent on the intracellular $Ca^{2+}$ concentration. From the above resuts, it is suggested that $Ba^{2+}$ activate indirectly the contractile process by promoting the mobilization of intracellular $Ca^{2+}$ and the influx of extracellular $Ca^{2+}$. It is also suggested that action of $Ba^{2+}$ on the $Ca^{2+}-activated$ $K^+$ channel can result in the depolarization of cell membrane in the rabbit renal artery.

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Effects of Cyclobuxine D on the Electrocardiogram (ECG) and Heart Rate in Anesthetized Rats and Isolated Frog Heart (Cyclobuxine D의 흰쥐에 있어서 ECG와 심박동수에 패한 작용과 적출 개구리 심장에 대한 작용)

  • Lee, Jong-Hwoa;Park, Young-Hyun;Cho, Byung-Heon;Kim, Yu-Jae;Kim, Jong-Bae;Kim, Chun-Sook;Cha, Young-Dong;Kim, Young-Suk
    • The Korean Journal of Pharmacology
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    • v.22 no.2
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    • pp.105-114
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    • 1986
  • This study was undertaken to search for a new antiarrhythmic agent in natural plants. Extracts of Buxus microphylla var. koreana Nakai have been used as folk remedies of several diseases, including malaria and venereal disease, but any study on the pharmacological actions of this plant has not yet been carried out and its active ingredients have not been identified. In our laboratory, we isolated buxuletin (nonalkaloid) and cyclobuxine D (steroidal alkaloid) from Buxus microphylla var. koreana Nakai and reported their pharmacological actions: diuretic effects of buxuletin in rabbits and hypotensive effect of cyclobuxine D in rats. In the present study, we investigated the effect of cyclobuxine D on isolated frog heart and heart rate in urethane anesthetized rats. In order to clarify the mechanism of bradycardic effect of cyclobuxine D, we examined the changes of the ECG parameters (PR, QRS and R ${\alpha}$ T interval) produced by intravenous injection of cyclobuxine D in anesthetized rats. Cyclobuxine D depressed the contractile force in isolated frog heart and exerted a dose-dependent bradycardic effect in anesthetized rats. Intracerebroventricular injection of cyclobuxine D caused a fall in blood pressure and an increase in heart rate, but those effects were not significant. Cyclobuxine D prolonged the PR interval and RaT interval (${\alpha}$ Tindicates the apex of T), but was without significant effects on the duration of the QRS complex and PRc in urethane anesthetized rats.

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In-vivo Studies on Effect of Lipo-PGE1 on Neoangiogenesis of Composite Graft in a Rabbit Model (가토모델에서 Lipo-PGE1이 복합조직이식편의 미세혈관신생에 미치는 영향)

  • Park, Ji-Ung;Eo, Su-Rak;Cho, Sang-Hun;Choi, Jong-Sun;Kim, Eo-Jin
    • Archives of Plastic Surgery
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    • v.37 no.6
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    • pp.721-725
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    • 2010
  • Purpose: The survival of composite graft is dependent on three steps, (1) plasmatic imbibitions, (2) inosculation, and (3) neovascularization. Among the many trials to increase the survival rate of composite graft, prostaglandin E1 (PGE1) has beneficial effects on the microcirculatory level with vasodilating, antithrombotic, anti-inflammatory and neoangiogenic properties. Lipo-PGE1 which is lipid microspheres containing PGE1 had developed to compensate the systemic and local side effects of PGE1. This study was proposed to determine whether Lipo-PGE1 administration enhanced the survival of composite graft through neovascularization quantitatively in a rabbit ear model. Methods: Fourteen New Zealand White Rabbits each weighing 3~4 kg were divided in two groups: (1) intravenous Lipo-PGE1 injection group and (2) control group. A $2{\times}1\;cm$ sized, full-thickness rectangular composite graft was harvested in each auricle. Then, the graft was reaaproximated in situ using a 5-0 nylon suture. For the experimental group, $3{\mu}g$/kg/day of Lipo-PGE1 ($5{\mu}g$/mL) was administered intravenously through the marginal vein of the ear for 14 days. The control group was received no pharmacologic treatment. On the 14th postoperative day, composite graft of the ear was harvested and immunochemistry staining used Monoclonal mouse anti-CD 31 antibody was performed. Neoangiogenesis was quantified by counting the vessels that showed luminal structures surrounded by the brown color-stained epithelium and counted from 10 random high-power fields (400x) by independent blinded observer. Statistical analysis (Wilcoxon Signed Ranks test for nonparametric data) was performed using SPSS v12.0, with values of p<0.05 considered significant. Results: The mean number of the microvessels was $15.48{\pm}8.65$ in the experimental group and $9.82{\pm}7.25$ in the control group (p=0.028). Conclusion: The use of Lipo-PGE1 facilitated the neoangiogenesis, resulted in the improvement of the survival rate of graft. On the basis of this results, we could support wider application of Lipo-PGE1 for more effective therapeutic angiogenesis and successful survival in various cases of composite graft in the human.

Effect of Bone Marrow Aspirate with Autogenous Bone graft for Alveolar Cleft in a new Rabbit Model (가토의 치조열 모델에서 골수 흡인물이 자가뼈 이식술에 미치는 효과)

  • Bae, Sung Gun;Chung, Ho Yun;Lee, Sang Yun;Cho, Byoung Chae;Yang, Jung Dug;Park, Mee Young
    • Archives of Plastic Surgery
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    • v.36 no.5
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    • pp.531-537
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    • 2009
  • Purpose: Alveolar bone grafting has become an essential process in the treatmemt of alveolar cleft patient for stabilization of the maxillary arch, elimination of oronasal fistula, the reconstruction of the soft tissue nasal base support, and creation of bony support for tooth eruption for implant. The use of Autologous iliac cancellous bone is preferable because of the adequate quantity and high osteoinductive potential. However, even with iliac bone, insufficient osteoregeneration and absorption occur due to several factors such as the patient's age, cleft width, functional stress, and others. In order to increase osteoregeneration where the iliac bone is placed, the present study is associated with bone marrow aspirate (BMA). The experimental study evaluated the efficacy of osteoregeneration in normal cleft rabbits when alveolar bone grafting was performed with autologous iliac corticocancellous bone. Methods: Twenty - four New Zealand White rabbits were divided randomly into 2 groups (BMA, control). All animals underwent harvesting of corticocancellous bone graft from the right posterior iliac crest via standard surgical technique. $1m{\ell}$ of BMA were obtained by scraping the needle and aspirate with $10m{\ell}$ syringe from the contralateral iliac bone wall. The muco - periosteal flap on the palate was elevated. A mixture of Equal bone's volumes with BMA and saline as its control was inserted into the cleft. Animals were sacrificed at 2, 4, and 8 weeks and maxilla was harvested for dental peri - apical X-ray, bone matrix density (BMD),and histologic analysis. Result: BMD of regenerated bone to the cleft in the rabbits was higher than that of the control rabbits. X-ray, histologic analysis showed that increased osteoregeneration and low absorption rate were observed in the BMA group. Conclusion: Our experimental study showed BMA enhanced the osteoregeneration and survival rate of alveolar bone grafting. BMA is easy to extract & cost - time effective. So it can be an effective enhancers for bone grafting mixtures.

Experimental Studies of the Pericardial Substitutes in Rabbits (가토에서 심낭대치물에 관한 실험적 연구)

  • Baeck, Seung-Hwan;Yang, Suk-Rhin;Kim, Sun-Han;Nam, Choong-Hee;Lee, Khil-Rho
    • Journal of Chest Surgery
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    • v.22 no.5
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    • pp.724-730
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    • 1989
  • The development of severe pericardial adhesion after cardiovascular surgical procedures often increases the risk of injuring the heart, great vessels, or extracardiac grafts during resternotomy. Several pericardial substitutes have been tested in an attempt to facilitate reoperation with inconclusive results. This study was designed to evaluate the applicability of two different materials as pericardial substitutes to minimize the pericardial adhesion and epicardial reaction. A procedure for induction of pericardial adhesion was carried out in 30 rabbits. Rabbits were divided into three groups of ten rabbits each: Group 1[control, simple pericardial closure]: Group 2[bovine pericardium as pericardial substitute]: Group 3[e-polytetrafluoroethylene surgical membrane, e-PTFE as a pericardial substitute]. Bovine pericardium or e-PTFE surgical membrane was interposed between the sternum and the heart. Rabbits were sacrificed at 4 weeks after operation. The development of adhesions and epicardial reactions were graded as: none [I]; minimal[II]; moderate[Ill]; and severe[1V]. Histologic studies of the substitute, the pericardium, and the epicardium were performed. The results were as follows; l. In group 1[control group], the degree of pericardial adhesions were grade I in none, grade II in 1, grade III in 3, and grade 1V in 6 animals. Epicardial reactions were grade I in none, grade II in 3, grade K in 4, grade 1V in 3 animals respectively. 2. In group 2[bovine pericardium], the degree of pericardial adhesions were grade I in 1, grade II in 5, grade III in 3, and grade 1V in 1 animal. Epicardial reactions were grade I in 1, grade II in 2, grade III in 4, and grade 1V in 3 animals respectively. 3. In group 3[e-PTFE], the degree of pericardial adhesions were grade I in 7 animals, grade II in 2, grade III in 1, and grade g in none. Epicardial reactions were grade I in 4, grade II in 3, grade III in 2, and grade IV in 1 animal respectively. Pericardial adhesions more than grade II were 90.9% in group 1, 40 % in group 2, and 10% in group 3. Pericardial adhesions were significantly reduced in group 3 compared to group 1 or 2. Epicardial reactions more than grade II were 70 % in group 1, 70 % in group 2 and 30 % in group 3. We concluded that this 0.1mm thick polytetrafluoroethylene surgical membrane is a suitable pericardial substitute to minimize the development of pericardial adhesion or epicardial reaction following cardiovascular surgery.

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Pre-and Post-ishemic Changes of the Constituent Enzymes in Isolated Rabbit's Myocardium (허혈전후 적출 가토 심근내의 구성 효소의 변화)

  • 천수봉;전도환;이재성;김송명
    • Journal of Chest Surgery
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    • v.33 no.2
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    • pp.117-124
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    • 2000
  • Background: Nucleoside transport inhibitor(NTI) Keeps AMP, ADP, ATP levels high in myocytes by inhibiting adenosine cataboilsm so that it may preserve the myocardial contractability during ischemia In this study we investigated the effects of cyclic AMP phosphodiesterase inhibor(C-AMP PDSI) and S-P-nitrobenzyl-6 -thioniosine(NBT; a sort of NIT) on myocadial preservation and changes of constituent enzyme. Material and method: Twenty-six isolated rabbit hearts were perfused with Krebs-Henseleit buffer solution for 20 minutes arrested for 20 minutes and ten reperfused for 30 minutes. The following four groups were prepared and hemodynamic changes coronary effluent lactate dehydrogenase (LDH) a-hydroxybutylic accid(a-HBD) levels and myocardial LDH creatine kinase-MB (CK-MB) adenosine deaminase(ADA) a-HBD levels and myocardial LDH creatine kinase-MB (CK-MB) adenosine deaminase(ADA) a-HBD levels were analysed before and after cardiac arest ; Group I(control) ; the heart was only perfused with K-H ; Group II ; the heart was perfused with K-H including C-AMP PDSI(Amrinone 25mg/L); Group III ; the heart was perfused with K-H including NBT(4.19mg/L) ; Group IV ; the heart was perfused with K-H including C-AMP PDSI + NBT. Result : Left venticular developed pressure(LVDP) at 10 minutes of the equilibrium was significantly higher in group III(72.1$\pm$5.3 mmHg p<0.01) and group III(72$\pm$5.6 mmHg P<0.025) as compared with group I (40.8$\pm$4.7mmHg) and LVDP at 20 minutes of the reperfusion was significantly higher in group II(74$\pm$5.3mmHg p<0.01) and group III(72$\pm$5.6mmHg p<0.025) as compared with group I (44.2$\pm$4.6mmHg). Percentage recovery of LVDP at the reperfusion was the highest in group II(123.3%) Percentage recovery of coronary flow at the equilibrium reperfusion were higher in group II(310%, 270%) group III(230%, 290%) group IV(310%, 280%) as compared with group I (100%) respectively. Myocadial LDH level was significant lower in group IV(33495$\pm$1802 IU/gm p<0.04) as compared with group I(48767$\pm$1421 IU/gm) Myocadial CK-MB level was significant higher in group II(74820$\pm$1421 IU/gm) compared with group I (45450$\pm$1737 IU/gm) Myocadial ADA level was significant higher group IV(1215$\pm$8 IU/gm p<0.05) compared with group I(125$\pm$15 IU/gm) but there was no significant difference between group I and group II ,III, IV in changes of coronary effluent LDH, a-HBD levels. Conclusion: C-AMP PDSI solely appears to have a better effect on myocardial preservation after ischemia than NBT but with no synergistic effect and it could keep CK-MB leve high in myocardial tissues.

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Effects of HwangRyunHaeDok-Tang and Constituent Herbs on a Contracted Artery of Rabbit (황련해독탕(黃連解毒湯)이 가토(家兎)의 혈관긴장성조절(血管緊張性調節)에 미치는 영향(影響))

  • Nam Chang-Gyu;Kim Ho-Hyun;Jeong Chan-Gil;Sung Hyun-Jea;Kwon Oh-Yul
    • The Journal of Internal Korean Medicine
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    • v.24 no.2
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    • pp.220-232
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    • 2003
  • Objective : The purpose of this study was to analyze the effects of HwangRyunHaeDok-Tang and combinations of constituent herbs on the arterial contraction. Methods : In order to investigate the effects Scutellariae Radix. Coptidis Rhizoma, Phellodendri Cortex and Gardeniae Fructus, in which one of them, two of them, and all of them, were used to exam. Results : The results were summarized as follows; 1. HwangRyunHaeDok-Tang significantly inhibited the contraction of artery induced by Norepinephrine(NE). However the atonic effect was slightly blunted when the vascular endothelial cell was removed. No significant change in the atonic effect of HwangRyunHaeDok-Tang was found when $_L-NNA$ was used as a preliminary treatment. These results indicate that the vascular atonic effect by HwangRyunHaeDok-Tang is slightly dependent on the endothelial cell, and that the HwangRyunHaeDok-Tang works directly to the vascular smooth muscle in creating the vascular atonic effect. 2. The pretreatment of HwangRyunHaeDok-Tang extract significantly inhibited the contractile response to additive application of $Ca^{2+}$ in the strips which were contracted by NE in $Ca^{2+}$-free solution. 3. HwangRyunHaeDok-Tang extract increased the contraction of arterial smooth muscle induced by KCl. Therefore, it can be concluded that HwangRyunHaeDok-Tang may block the NE-receptor or receptor-operated $Ca^{2+}$ channel. 4. It was determined that Scutellariae Radix, Coptidis Rhizoma and Phellodendri Cortex among the ingredients of HwangRyunHaeDok-Tang have a vascular atonic effect. In addition, those ingredients plays a role in strengthening the atonic effect by working with other herbal medicines. Gardeniae Fructus causes the blood vessel to contract. but it does not influence the atonic effects of other herbal medicines. However Gardeniae Fructus tends to inhibit the vascular atonic effect of Phellodendri Cortex. Conclusion : Based on the above results, it can be said that HwangRyunHaeDok-Tang can be applied to cure hypertension considering those three herbs have significant effects of relaxation.

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FABRICATION OF MYOMUCOSAL FLAP USING CULTURED ORAL EPITHELIUM IN RABBIT MODEL (가토모델에서 배양 구강상피를 이용한 근-점막 피판의 형성에 관한 연구)

  • Shin, Young-Min;Chung, Hun-Jong;Ahn, Kang-Min;Park, Hee-Jung;Sung, Mi-Ae;Kim, Soung-Min;Hwang, Soon-Jung;Kim, Myung-Jin;Jahng, Jeong-Won;Kim, Sung-Po;Yang, Eun-Kyung;Song, Kye-Yong;Lee, Jong-Ho
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.27 no.3
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    • pp.226-237
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    • 2005
  • Purpose : Extensive defect of oral and maxillofacial area is usually reconstructed with composite flap including skin paddle. However, if the defects are lined with only skin components, the mucosa's role in mastication and texture are not restored. Furthermore, stiffness and hair-growing prevent denture rehabilitation and good oral hygiene. This study was performed to overcome the disadvantages of composite soft tissue flaps including the skin and to make a model for myo-mucosal flaps. Materials and methods : Buccal mucosa sized $0.5\times1.0\;cm^2$ from New Zealand rabbit (around 1.5kg) was harvested and cultivated by the modification of Rheinwald and Green's keratinocyte culture method. Cultured mucosa was grafted on the fascia of latismus dorsi as form of mucosal sheet. After 7, 10, 14 days, the myomucosal flap was excised and evaluated under light microscope with H & E and immunohistochemical staining. As control group, harvested buccal mucosa from rabbit was transplanted to gracilis muscle(n=6). Results : From 7 days after prelamination, the basal layer of the grafted mucosa resembled that of normal mucosa. As control group, transplanted mucosa had original shape but there's slight inflammatory reaction. Prelaminated mucosa has 19.8$\pm$4.59 cell layers and some samples have more than 20 layers. The expression rate of PCNA was relatively strong (42.9%$\pm$14.1) at the basal layer of grafted mucosa and the laminin was found at the basal layer. On the contrary, prelaminated mucosa at 10 days showed moderate expression rate of PCNA(32.4%$\pm$4.62). We found the mucosal layer was somehow disappeared and there is strong inflammatory reaction. After 14 days prelamination, the grafted oral keratinocytes were almost disappeared and expression of PCNA was not observed. Conclusion : We can make 75 fold large mucosal($3850mm^2$) sheet from small samples of mucosa $(50mm^2)$. Epithelial sheet that grafted on the fascia of muscle underwent differentiation and proliferation. But after 10, 14 days, there was strong inflammatory reaction and the grafted mucosa was destroyed from surface layer. In rabbit model, transfer of fascio-mucosal flap should be done from 7 to 10 days after prelamination.

Effects of Chronic Treatments with 5-HT Uptake Inhibitors on the [$^3H$]Imipraine and [$^3H$]Paroxetine Binding, [$^3H$]5-HT Uptake, and 5-HT Content of the Rabbit Platelet (5-HT 흡수억제성 항우울제들이 가토혈소판의 [$^3H$]Imipramine과 [$^3H$]Paroxetine Binding, [$^3H$]5-HT 흡수, 및 5-HT함량에 미치는 영향)

  • Won, Kyong-Sik;Lee, Min-Soo;Shin, Kyung-Ho;Chun, Boe-Gwun;Kwak, Dong-Il
    • Korean Journal of Biological Psychiatry
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    • v.1 no.1
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    • pp.88-97
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    • 1994
  • Many evidences are compatible with the correlation between the inhibition of [$^3H$] imipramine([$^3H$]IMI) and [$^3H$]paroxetine([$^3H$]PAT) binding to the 5-hydroxytryptamine(5-HT) transporter complex and the 5-HT uptake of 5-HT neurons and platelets, and most antidepressants have been shown to inhibit the [$^3H$]IMI and [$^3H$]PAT binding and the neuronal 5-HT uptake. However, several paradoxical research findings led to doubt about the pharmacological significance of the [$^3H$]IMI and [$^3H$]PAT binding sites. This study was carried to clarify the correlation between the [$^3H$]IMI and [$^3H$]PAT binding parameters and the tissue 5-HT content or/and [$^3H$]5-HT uptake in the rabbit platelet, which contains 40 times ad much 5-HT as that of human platelet and shows the 10 fold higher $B_{max}$ of the 5-HT transporter binding to a 5-HT uptake inhibitor. The rabbits were treated for 28 days with amitriptyline(4mg/kg/day : AP), fluoxetine(0.5mg/kg/day : FO), and sertraline(0.5mg/kg/day : SA) via an Alzet osmotic pump implanted for constant infusion. The [$^3H$]IMI binding $B_{max}$ and $K_d$ of the rabbit platelets were $6.4{\pm}1.2$pmol/mg protein and $10.9{\pm}2.1$nM and those in the [$^3H$]PAT binding were $8.6{\pm}1.1$pmol/mg protein and $1.6{\pm}0.3$nM, respectively. AP slightly increased $B_{max}$ of [$^3H$]IMI binding and both [$^3H$]IMI binding and [$^3H$]PAT binding $K_d$, and i contrast, it slightly decreased $B_{max}$ of [$^3H$]PAT binding. FO Slightly increased $K_d$ of both and [$^3H$]IMI and [$^3H$]PAT binding and slightly decreased $B_{max}$ of [$^3H$]IMI and [$^3H$]PAT binding. SA produced the significant increase of [$^3H$]PAT binding $B_{max}$ and the slight increase of both [$^3H$]IMI and [$^3H$]PAT binding $K_d$ and in contrast, it slightly decreased $B_{max}$ and of [$^3H$]IMI binding. And, the $V_{max}$ and $K_m$ of platelet [$^3H$]5-HT uptake were $24.2{\pm}2.4$pmol/$10^8$ platelets/min and $3.3{\pm}0.3$nM, respectively. The $V_{max}$ was little affected by AP, FO, or SA, but the [$^3H$]5-HT uptake $K_m$ value was moderately increased by FO. However, the platelet 5-HT content was moderately decreased by all of the 5-HT uptake inhibitors used in this study. These results seem to be consistent with the allosterical and competitive interaction of 5-HT uptake inhibiting antidepressants with each other as well as 5-HT in the 5-HT transporter binding, and provide no support for the view that the potencies of 5-HT uptake inhibitors to inhibit the [$^3H$]IMI or [$^3H$]PAT binding with 5-HT transporter complex correlate with their antidepressant potencies.

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Influence of Blockade of Sympathetic Nervous System, Renin-Angiotensin System, and Vasopressin System on Basal Blood Pressure Levels and on Pressor Response to Norepinephrine, Angiotensin II, and Vasopressin (교감신경계, Renin-Angiotensin계, Vasopressin계의 차단이 혈압 및 Norepinephrine, Angiotensin II 및 Vasopressin의 승압효과에 미치는 영향)

  • Chung, Haeng-Nam
    • The Korean Journal of Pharmacology
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    • v.28 no.1
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    • pp.61-74
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    • 1992
  • Influence of the blockade of the three major pressor systems-sympathetic nervous system (SNS), renin-angiotensin system (RAS) and vasopressin system-on the pressor responsiveness to norepinephrine (NE), angiotensin II (AII), and vasopressin (VP) as well as on basal blood pressure (BP) levels was investigated in urethane-anesthetized rabbits. To block the SNS and RAS, chlorisondamine (CS) and pirenzepine (PZ), sympathetic ganglionic blockers, and enalapril (ENAL), an inhibitor of angiotensin converting enzyme, respectively were used. And for suppressing the VP system bremazocine (BREM), a kappa opiate receptor agonist shown to suppress plasma levels of VP, was employed. Each of CS (0.4 mg/kg), ENAL (2 mg/kg), and BREM (0.25 mg/kg) produced almost same levels of steady hypotensive state. The hypotensive effect of BREM was significantly attenuated by desmopressin, a synthetic VP-like analogue, suggesting the hypotension being at least in part due to suppression of plasma levels of VP. CS, ENAL and BREM elicited further fall of the BP which had been lowered by ENAL or BREM, CS or BREM, and CS or ENAL, respectively. The hypotension produced by both CS and PZ together with either of ENAL or BREM was more marked than that produced by the three drugs other than CS. CS potentiated the pressor response not only to NE but to AII and VP. The pressor effect of AII was increased by ENAL and BREM, too. The pressor response to VP was also enhanced by BREM. Blockade of ${\alpha}-adrenergic$ receptors with phentolamine or phenoxybenzamine potentiated the pressor response to AII and that to VP. The results on basal BP levels indicate that the three major pressor systems are all participating in control of BP, but SNS has the greatest potential for supporting BP. The finding that blockade of one of the pressor systems induced enhanced pressor responsiveness to the pressor hormone of that particular system as well as to the pressor hormone(s) of the other systems(s) provides evidence for important interactions among the three major pressor systems.

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