• Title, Summary, Keyword: adrenoceptor

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Effects of $\alpha$-Adrenoceptor Antagonists on Phenylephrine-induced Contraction in the Endothelium-denuded Rat Aorta (내피세포를 제거한 흰쥐 대동맥에서 Phenylephrine이 일으킨 수축반응에 대한 $\alpha$-수용체 길항제의 영향)

  • 홍승철;강맹희;박상일;박미선;최수경;정준기;서석수
    • YAKHAK HOEJI
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    • v.35 no.5
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    • pp.416-426
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    • 1991
  • The effects of an irreversible or a reversible $\alpha_1$-adrenoceptor antagonist (dibenamine or prazosin) on $\alpha_1$-adrenoceptor-mediated vasoconstrictions were studied in the endothelium-denuded rat aorta. In these experiments, the mobilization of intracelluier calcium and translocation of extracellular calcium were also studied. To exclude the modulation of endothelium releasing EDRF and EDCF, the endothelium was removed in all rat aortas. Contraction induced by phenylephrine (a full $\alpha_1$-adrenoceptor agonist) was separated into a fast phasic component of the response due to the release of intracellular calcium and a slow tonic one due to the influx of extracellular calcium. Pretreatments with increasing doses of reversible $\alpha_1$-adrenoceptor antagonist prazosin, as well as irreversible $\alpha_1$-adrenoceptor antagonist dibenamine, inhibited the phasic component of phenylephrine-induced contraction more effectively than the tonic one. Pretreatment of dibenamine (0.2 $\mu{M}$) or prazosin (10 nM) to the rat aorta abolished phasic response but remained tonic one about 41% and 51%, respectively. These results suggest that as the efficiency of phenylephrine was progressively reduced by pretreatments with increasing doses of an irreversible or a reversible $\alpha_1$-adrenoceptor antagonist (dibenamine or prazosin), the contraction induced by phenylephrine became progressively more dependent on the influx of extracellular calcium.

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Control of Parturition Time on Pig II. Effect of Sympathetic Nerve and Adrenergic Agonist on Uterine Smooth Muscle Motility (돼지 분만 시기의 조절에 관하여 II. 자궁 평활근의 운동성에 대한 교감신경과 Adrenergic Agonist의 영향)

  • 심철수;이양성;임종옥
    • Korean Journal of Veterinary Service
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    • v.17 no.3
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    • pp.255-263
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    • 1994
  • To elucidate the action of the adrenergic nerve on the isolated uterine smooth muscle of the pig, effects of electrical transmural nerve stimulation and norepinephrine were investigated on the pretreatment of phentolamine ; non-selective ${\alpha}$-adrenoceptor blocker, propranolol ; ${\beta}$-adrenoceptor blocker and the yohimbine;${\alpha}_2$-selective adrenoceptor blocker from physiograph. 1. The relaxation response induced by norepinephrine was the concentration of $10^{-6}$ M at first and maximum response was concentration of $10^{-4}$M. 2. The relaxation response induced by norepinephrine was not effected by the pretreatment with non-selective $\alpha$-adrenoceptor blocker, phentolanune ($10^{-6}$ M) but was completely blocked by the pretreatment with ${\beta}$-adrenoceptor blocker, propranolol($10^{-6}$ M). 3. The contractile response induced by electrical transmural nerve stimulation(20V, 10Hz, 0.5msec, 20sec ) was inhibited by the pretreatment with non-selective ${\alpha}$-adrenoceptor blocker, phentolamine($10^{-6}$ M) but was not inhibited and rather increased by the pretreatment ${\beta}$-adrenoceptor blocker, propranolol($10^{-6}$ M), and was not approximately effected by the pretreatment with ${\alpha}_2$-adrenoceptor blocker, yohimbine($10^{-6}$ M). These finding suggest that it was excitatory action by ${\alpha}_1$-adrenergic nerve and inhibitory action by ${\alpha}_2$-adrenergic, ${\beta}$-adrenergic nerve on uterine smooth muscle of the pig.

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Effects of ${\alpha}_1-Adrenergic$ Stimulation on Membrane Potential, Twitch Force, Intracellular $Na^+,\;and\;H^+$ Activity in Hyperthyroid Guinea Pig Ventricular Muscle (갑상선 기능 항진 기니픽 심근에서 ${\alpha}_1-Adrenergic$ 수용체 자극이 막전위, 수축력 및 세포내 $Na^+$$H^+$ 활성도에 미치는 영향)

  • Kim Jin-Sang;Chae Soo-Wan;Cho Kyu-Park
    • The Korean Journal of Pharmacology
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    • v.31 no.1
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    • pp.39-51
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    • 1995
  • The roles of ${\beta}-adrenoceptor$ were well known in hyperthyroidal heart, but not with ${\alpha}-adrenoceptor$. So we studied the effects of phenylephrine on membrane potential, intracellular sodium activity ($a^{i}_{Na}$), twitch force, and intracellular pH ($pH_i$) by continuous intracellular recordings with ion-selective and conventional microelectrodes in the papillary muscles of hyperthyroid guinea pig heart. ${\alpha}_1-adrenoceptor$ stimulation by phenylephrine (10^{-5}\;or\;3{\times}10^{-5}M$) produced the following changes: variable changes in action potential duration, a hyperpolarization ($1.5{\pm}0.1mM$) of the diastolic membrane potential, an increase in $a^{i}_{Na}\;(0.4{\pm}0.15mM)$, a stronger positive inotropic effect ($220{\pm}15%$), an increase in $pH_i\;(0.06{\pm}0.002\;unit)$. These changes were flocked by prazosin and atenolol. This indicated that the changes in membrane potential, $a^{i}_{Na}$ twitch force, and $pH_i$ are mediated by a stimulation of the ${\alpha}_1-adrenoceptor$. Ethylisopropylamiloride ($10^{-5}$) also blocked the increase in $a^{i}_{Na}$ and twitch force. On the other hand, strophanthidin, tetrodotoxin, $Cs^+$ or verapamil did not block the increase in $a^{i}_{Na}$ and twitch force. Thus, it was suggested that ${\alpha}_1-adrenoceptor$ stimulation increased $a^{i}_{Na}\;and\;pH_i$ by stimulation of $Na^{+}-H^{+}$ exchange, thereby allowing intracellular alkalinization and $a^{i}_{Na}$ increase. These results were very different from euthyroidal heart which showed ${\alpha}_1-adrenoceptor$-induced decrease in $a^{i}_{Na}$ and initial negative inotropic effect. From the above results, it was concluded that ${\alpha}_1-adrenoceptor$ had a important role in hyperthy-roidal heart.

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Possible Relationship between Hyperactivity of Central $_{{\alpha}2_}$-Adrenoceptors and Muricidal Behavior in Olfactory Bulbectomized Rats (후신경구절제 흰쥐에서 Muricide 발생기전으로서 $_{{\alpha}2_}$-Adrenoceptors의 기능항진에 관한 연구)

  • Lee Won-Suk;Rhim Byung-Yong;Hong Ki-Whan
    • The Korean Journal of Pharmacology
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    • v.22 no.1
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    • pp.45-50
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    • 1986
  • The involvement of central $_{{\alpha}2}$-adrenoceptors in the development of muricide (mouse-killing behavior) in the olfactoly bulbectomized (OB) rats was strudied. The fractional turnover rate of noradrenaline (NA) in forebrain from OB muricidal rats was significantly lowered than that from sham rats. However, after yohimbine or idazoxan treatment, NA turnover was significantly increased in concert with inhibition of the development of muricide in OB rats. By radioligand binding studies with $[^3H]$ yohimbine, the maximum binding $(B_{max})$ of $[^3H]$ yohimbine to cerebral cortical membrane from OB rats was significantly higher than that from sham rats without change of affinity for agonists and antagonists$(K_i)$. With these results it was suggested that muricidal behavior of OB rats has a close relevance to the hyperactivity of central $_{{\alpha}2}$-adrenoceptor system.

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Effects of the Endothelium on the Contractile Responses to Norepinephrine in Isolated Proximal and Distal Coronary Artery of Pigs

  • Kim, Jong-Hoon;Jeon, Byeong-Hwa;Chang, Seok-Jong;Park, Hae-Kun
    • The Korean journal of physiology & pharmacology
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    • v.27 no.1
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    • pp.27-35
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    • 1993
  • Effects of the endothelium on the contractile responses to norepinephrine (NE) were investigated in isolated helical strips of the proximal and distal coronaries artery of pigs. The helical strips were immersed in Tris-buffered Tyrode's solution equilibrated with 100% $O_2$ at $35^{\circ}C$ and its isometric tension was measured. NE relaxed the strips precontracted with acetylcholine from both the proximal and distal coronary artery. NE-induced relaxation, which might be induced mainly by $\beta$-adrenoceptor function was dominant in the distal coronary arteries. NE-induced relaxation was converted to a contraction after $\beta$-adrenoceptor blockade with propranolol $(3{\times}10^{-6}M)$. ${\alpha}$-adrenoceptor-mediated contraction by NE was greater in the proximal coronary artery than the distal coronary artery. Quantitatively, ${\alpha}_1$-adrenoceptor mediated contraction by NE was greater than ${\alpha}_2$-adrenoceptor mediated contraction by NE in both arteries. NE-induced relaxation was decreased by rubbing of endothelium in both arteries. ${\alpha}_1-and\;{\alpha}_2$-adrenoceptor mediated contraction by NE were potentiated by rubbing of endothelium in both arteries. Pretreatment with methylene blue, an inhibitor of soluble guanylate cyclase, increased ${\alpha}_1-\;and\;{\alpha}_2$-adrenoceptor mediated contraction by NE in both arteries with endothelium. From the above results, we suggest that the effect of activation of $\alpha$-adrenoceptors by NE may be modulated by endothelium in the proximal and distal coronary arteries of pigs. This effect may be mediated via endothelium derived relaxing factor.

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Effects of α1-adrenoceptor stimulation on Mg2+ release in perfused guinea pig heart (관류 기니픽 심장에서 Mg2+ 유리에 미치는 α1-adrenoceptor 자극효과)

  • Hwang, Sung-chul;Kim, Sang-jin;Kang, Hyung-sub;Lee, Seung-ok;Kang, Chang-won;Kwon, Oh-deog;Kim, Jin-sang
    • Korean Journal of Veterinary Research
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    • v.36 no.2
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    • pp.327-335
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    • 1996
  • Recently in spite of the interest on the regulation of intracellular $Mg^{2+}$ by neurotransmitters or drugs, the magnesium ion($Mg^{2+}$) regulation by ${\alpha}_1$-adrenoceptor stimulation has not been studied in the heart yet. To elucidate the regulation of ${\alpha}_1$-adrenoceptor stimulation-induced $Mg^{2+}$ release and the effects of ${\alpha}_1$-adrenoceptor stimulation on pathophysiological conditions, in this study we have evaluated the effects of phenylephrine, PMA, $H_7$. staurosporine, verapamil and lidocaine on $Mg^{2+}$ release in perfused guinea pig heart. During preperfusion exogenous $Mg^{2+}$ was added to the medium to give 1.2mM 15min before starting to addition of drugs, and then the infusion of exogenous $Mg^{2+}$ was stopped. $Mg^{2+}$ in the perfusate leaving the heart was measured by atomic absorption spectrophotometry. $Mg^{2+}$ free solution produced an increase in heart rate and phenylephrine elicited $Mg^{2+}$ release from the heart. $Mg^{2+}$ release by phenylephrine was abolished by combined treatment with prazosin. By contrast, cardiac $Mg^{2+}$ uptake induced by a protein kinase C(PKC) activator, PMA was abolished by a selective PKC inhibitor, staurosporine. And the phenylephrine-induced $Mg^{2+}$ release was not affected by the PKC inhibitor, $H_7$. When verapamil or lidocaine was added to perfusing solution, $Mg^{2+}$ release was potentiated by phenylephrine from perfused guinea pig heart. These results suggest that ${\alpha}_1$-adrenoceptor stimulation caused $Mg^{2+}$ release and that PKC is not involved in ${\alpha}_1$-adrenoceptor mediated $Mg^{2+}$ release from perfused guinea pig heart. Under pathophysiological conditions, the $Mg^{2+}$ alteration by ${\alpha}_1$-adrenoceptor stimulation is considerable.

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Synthesis of Tetrahydrocarbazole Derivatives as Potent β3-Adrenoceptor Agonists

  • Ha, Jae-Du;Kang, Seung-Kyu;Cheon, Hyae-Gyeong;Choi, Joong-Kwon
    • Bulletin of the Korean Chemical Society
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    • v.25 no.12
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    • pp.1784-1790
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    • 2004
  • A series of 2-(3-chlorophenyl)-2-hydroxyethylamine derivatives containing a tetrahydrocarbazole linker were prepared and evaluated for their ${\beta}_3$-adrenoceptor agonistic activity. Several compounds showed potency comparable to CL-316243.

Effects of melatonin on heart rate and blood pressure in rat I. Effects on blood pressure (멜라토닌이 랫트에서 심박수 및 혈압에 미치는 효과 I. 혈압에 미치는 효과)

  • Oh, Sung-suck;Kim, Shang-jin;Kim, Jin-shang
    • Korean Journal of Veterinary Research
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    • v.41 no.3
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    • pp.327-332
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    • 2001
  • In recent years, experimental evidence have been suggested that melatonin has either contractive or relaxing effects on the vascular smooth muscle in vitro. But the effect of melatonin on the cardiovascular system in vivo had been emphasized about the hypotensive effect. In this work, we found not only hypotensive effect but also hypertensive effect of melatonin in rats and attempted to determine the mechanism of these effects elicited by melatonin. Regadless of concentration, melatonin(0.002~5 mg/kg) produced increase in mean blood pressure (MBP) in 36% (54/150 cases) and decrease in mean blood pressure in 64%(96/150 cases). As a whole melatonin caused an increase or a decrease in MBP without compensatory decrease or increase in heart rate. The melatonin-induced hypertension was abolished by the pretreatment of phenoxybenzamine, a ${\alpha}$-adrenoceptor antagoninst. The melatonin-induced hypotension was abolished by the pretreatment of propranolol, a ${\beta}$-adrenoceptor antagonist, ODQ, a NO-sensitive guanylate cyclase inhibitor, or nifedipine, a L-type $Ca^{2+}$ channel blocker, but not by bilateral cervical vagotomy. The results indicate that melatonin-induced hypertension may be related to ${\alpha}$-adrenoceptor stimulation and melatonin-indued hypotension may be related to ${\beta}$-adrenoceptor stimulation, inhibition of $Ca^{2+}$ channel and/or activation of guanylate cyclase.

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Studies on Adrenoceptors Involved in Regulation of Sodium Transport in Frog Skin (개구리 피부에 있어서 Na 수송을 조절하는 Adrenoceptors에 관한 연구)

  • Choi Bong-Kyu;Kim Kyung-Keun;Kim Heung-Kyu;Kook Young-Johng
    • The Korean Journal of Pharmacology
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    • v.22 no.1
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    • pp.24-33
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    • 1986
  • To ascertain the existence of various adrenoceptors involved in active transport of sodium in the frog skin and to delineate their physiological roles, the influence of various adrenergic agonists and antagonists on the potential difference (PD), short-circuit current (SCC) and total skin conductance (TSC) of the isolated frog skin of Rana nigromaculata were investigated. PD and SCC were determined with Ussing's technique. Drugs were administered to the serosal side of the skin. Experimental results were summarized as follows: 1. The responses to norepinephrine (NE, $6{\times}10^{-8}-6{\times}10^{-5})M$), phenylephrine (PE, $5{\times}10^{-6}-5{\times}10^{-4}M$) and epinephrine (Epi, $5.5{\times}10^{-7}-5.5{\times}10^{-5}M$) were characterized by marked elevation of PD & SCC in dose-related fashion, but the maximal effect attained by Epi was less than those of NE and PE. 2. These increments of PD & SCC were significantly inhibited by prazosin $(2{\times}10^{-6}M)$, a speciflc ${\alpha}_1$-adrenoceptor blocker. The stimulatory effect on PD & SCC were completely abolished by phenoxybenzamine (PBZ, $3.3{\times}10^{-5}M$), an irreversible ${\alpha}$-adrenoceptor blocking agent. Furthermore, with a larger doses of Epi produced marked decline of PD & SCC after the PBZ pretreatment. 3. Isoproterenol (ISP), a ${\beta}$-adrenoceptor agonist, in concentrations ranging from $5{\times}10^{-7}$ to $5{\times}10^{-6}M$ produced dose-related decrease in PD & SCC, which could be abolished by pretreatment with propranolol $(4{\times}10^{-6}M)$, a specific ${\beta}$-adrenoceptor blocker. It was further noted that the effects of Epi on PD & SCC were markedly potentiated by Propranolol pretreatment. 4. Clonidine as well as guanabenz produced increases in PD & SCC and these effects were inhibited more specifically by prazosin pretreatment than by yohimbine. These results indicated that there exist in the frog skin two distinctive types of adrenoceptors, ${\alpha}$ and ${\beta}$, which roughly corresponds to those in mammals, and that the ${\alpha}$ type of adrenoceptors mediate the stimulation of PD & SCC, whereas ${\beta}$-adrenoceptors mediate the inhibition. However, based on evidence at hand, no conclusion could be drawn on the subtype of ${\alpha}$-adrenoceptors which is involved in the stimulation of sodium transport in the frog skin.

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The association between polymorphisms of ${\beta}$-adrenoceptors and preeclampsia

  • Lim, Ji-Hyae;Kim, Shin-Young;Park, So-Yeon;Yang, Jae-Hyug;Han, Jung-Yeol;Hong, Dal-Soo;Choi, June-Seek;Choi, Kyu-Hong;Ryu, Hyun-Mee
    • Journal of Genetic Medicine
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    • v.4 no.2
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    • pp.160-166
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    • 2007
  • Purpose : The ${\beta}$-adrenoceptors are pharmacologically classified into ${\beta}_1$-, ${\beta}_2$- and ${\beta}_3$-adrenoceptor. The gene of each subtype has polymorphisms related to their function (${\beta}_1$-adrenoceptor: Ser49Gly, ${\beta}_2$-adrenoceptor: Gln27Glu, ${\beta}_3$-adrenoceptor: Trp64Arg). The objectives of this study were to analyse the allelic and genotypic distribution of the representative polymorphism of ${\beta}$-adrenoceptors in preeclampsia and to investigate whether combined genotype of ${\beta}$-adrenoceptors may be associated with preeclampsia. Methods : Blood samples were collected from a Korean population (159 preeclamptic pregnancies and 168 normotensive pregnancies). The ${\beta}_1$-, ${\beta}_2$- and ${\beta}_3$-adrenoceptor genotypes was determined using polymerase chain reaction-restriction fragment length polymorphism. Results : There were no differences in allelic and genotypic distribution of ${\beta}_1$- and ${\beta}_2$-adrenoceptor polymorphisms between the two groups. However, the Arg allele of ${\beta}_3$-adrenoceptor polymorphism were more frequent in preecalmpsia than in controls (P<0.05, OR=1.57, 95% CI=1.01-2.46). Moreover, prevalence of genotype carrying heterozygote of ${\beta}_3$-adrenoceptor polymorphism was increased in preeclampsia compared with controls (P<0.05, OR 1.76, 95% CI 1.06-2.92). When combination of the three polymorphisms were evaluated, pregnancies with the particular combined genotype that is consisted of heterozygote of ${\beta}_1$-, ${\beta}_3$-adrenoceptor and wild homozygote of ${\beta}_2$-adrenoceptor (Ser/Gly, Gln/Gln, Trp/Arg), showed a significant increase in the risk of preeclampsia (P<0.05, OR=3.01, 95% CI 1.12-8.08). Conclusion : A particular combined genotype (Ser/Gly, Gln/Gln, Trp/Arg) of - adrenoceptors was associated with the risk of preeclampsia.

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