• 제목/요약/키워드: muscarinic acetylcholine receptor

검색결과 62건 처리시간 0.037초

콜린성 및 아드레날린성 신경전달물질에 의한 이스라엘잉어 복대동맥의 혈관긴장도 조절기능 (Vasomotor Regulation of the Israeli Carp (Cyprinus carpio) Ventral Aorta by Cholinergic and Adrenergic Neurotransmitters)

  • 박관하
    • 한국어류학회지
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    • 제12권1호
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    • pp.38-45
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    • 2000
  • 어종에 따라 혈관의 긴장도 조절은 다양한 신경전달물질에 의하여 조절되고 있다. 그러나 아직 대부분의 어종에서 자율신경계 신경전달물질 및 혈관긴장도 조절인자들의 기능에 대하여 명확하게 규명되어 있지 않다. 본 연구는 아직 연구되지 않은 분야인 이스라엘잉어에서의 자율신경계 신경전달물질들의 혈관긴장도 조절에서의 역할을 규명하고자 적출복대동맥을 이용하여 시험하였다. 이 적출혈관에서 아세틸콜린 (ACh)은 정상혈관과 미리 일정수준 수축시킨 혈관 모두에서 수축을 유발하였으며 수축작용은 무스카린성 길항제인 아트로핀에 의해 거의 완벽하게 차단되었다. 여러 가지 아드레날린성 수용체를 동시에 흥분시키는 내인성 물질인 에피네프린 (Epi)은 혈관의 조건에 상관없이 이완반응을 유발하였다. 그러나 유사한 내인성물질인 노르에피네프린 (NE)은 정상혈관에서는 미약한 수축율, 미리수축된 혈관에서는 이완작용을 유발하였다. 한편 ${\alpha}_1$ 아드레날린성 수용체 흥분제인 페닐에프린은 수축을, $\beta$수용체 홍분제인 이소프로테레놀은 이완을 각각 유발하였으며 ${\alpha}_2$수용체 흥분제인 클로니딘은 아무런 반응을 유발하지 않았다. Epi, NE 및 이소프로테레놀에 의해 유발된 혈관이완 반응은 $\beta$ 아드레날린성 수용체 길항제인 프로프라놀롤에 의해 유의하게 억제되었다. 따라서 살아있는 상태의 이스라엘 잉어에서는 ACh는 주로 무스카린성 수용체 활성화에 의한 혈관을 수축하는 기능을, Epi과 NE는 $\beta$수용체 흥분에 의한 이완작용을 각각 발휘하는 것으로 판단된다.

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개 신동맥 내피세포의 무스카린성 및 알파 아드레날린성 수용체에 대한 작용 (Responsiveness of Muscarinic and Alpha Adrenergic Activation on Endothelial Cell in Isolated Canine Renal Arteries)

  • 정수연;장기철;임정규
    • 대한약리학회지
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    • 제25권1호
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    • pp.43-51
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    • 1989
  • 내피세포가 잘 보존된 개 신동맥에서 Phenylephrine으로 전 수축시킨 후 Actylcholine을 투여하면 혈관 이완을 관찰할 수 있었지만 내피세포를 파괴시킨 개 신동맥에서는 혈관 이완을 관찰할 수 없었으므로 내피세포가 혈관 이완에 관여함을 알 수 있었다. 그래서 내피세포에서 분비되어 혈관 이완을 촉진하는 물질을 Endothelium Dependent Relaxation Factor (EDRF)라고 한다. Acetylcholine에 의한 혈관 이완은 Atropine에 의해 경쟁적으로 억제되었으므로 Muscarinc 수용체의 자극을 받아 EDRF가 분비되고 이것이 평활근에 작용하여 이완을 일으킬 것으로 생각되었다. EDRF의 작용기전을 알아보기 위해 용해성 Guanylate cyclase 억제제인 Methylene blue를 전처치 했을 때는 Acetylcholine 뿐 만 아니라 Sodium nitroprusside에 의한 이완도 억제되었다. 그러나 Prostacyclin에 의한 이완은 억제되지 않았다. 이 결과로 판단 해 보면 EDRF에 의한 이완효과가 Cyclic GMP와 관련이 있을 것으로 생각되었다. 한편 Thromboxane $A_2$ 유사체인 U-46619로 전수축 시킨 후 Alpha-2 아드레날린성 항진제인 Clondine을 투여했을 때 혈관 이완은 일어나지 않았다. 수축의 억제 양상에 있어서 Alpha-1 아드레날린성 항진제인 Phenylephrine보다 Clonidine이 더 효과적 이었다. 이상의 결과를 기초로 하여 다음과 같은 결론을 얻을 수 있었다. 1) Muscarinic 수용체의 자극을 받아 EDRF의 분비가 촉진된다. 2) Alpha-1 아드레날린성 수용체와 Alpha-2 아드레날린성 수용체가 개 신동맥에 존재한다. 3) EDRF에 의한 이완이 Methylene blue에 의해서 억제되므로 cGMP를 이용한 기전 임을 알 수 있었다.단요수근신건과 외상과의 변화를 알 수 있으며 진단에 있어서 보조적인 역할을 할 수 있다. 하지만, 치료 후 증상 호전 도달기간의 예후 판정에는 크게 도움이 되지 않는다. 시술과정에서 코일의 이탈이 2예에서 발생하였으나, 모두 snare기법으로 제거되었고, 그 밖의 다른 합병증은 없었다. 결론: 만성골반통을 일으키는 골반울혈증후군의 치료에 있어서 코일을 이용한 난소정맥색전술은 단기추적검사상 다수에서 증상의 소실 및 완화를 보여 비교적 효과적이고 안전한 방법으로생각되며, 다른 병인이 공존하지 않는다면 기존의 수술적 치료를 대치할 수 있는 훌륭한 중재적 치료법으로써 이용될 수 있을 것으로 사료된다. 있게 큰 수치를 보였다. 결론: 정상 두개내혈관 직경은, 성별 차이가 40대에서 분명하였고 남자가 여자에 비하여 크거나 큰 경향을 보였으며, 중뇌동맥 직경은 성별에 상관없이 고령층이 저령층에 비하여 의미있게 크거나 큰 경향을 나타내었다. 고령층의 중뇌동맥 근위부 직경은 남자가 2.59$\pm$0.35 mm, 여자가 2.38$\pm$0.37 mm이었고, 원위부 직경은 남자가 2.63$\pm$0.43 mm, 여자가 2.39$\pm$0.35 mm 이었다.고 Monaliza Finely Soft는 23% 더 높은 분리율을 나타냈으므로 선충분리용(線蟲分離用)으로는 향수처리(香水處理)되지 않은 것이 더 좋은 것으로 사료(思料)된다. 4. 온도별(溫度別) 선충분리율(線蟲分離率)을 $15^{\circ},\;25^{\circ}\;and\;35^{\circ}C$에서 조사(調査)한 결과(結果) 전체적(全體的)으로 $35^{\circ}C$에서 분리율(分離率)이 가장 높게 나타났다. 5. 시간경과(時間經過)에 따른 선충분리율(線蟲分離率)은 12시간(時間) 후(後)가 35.3 %이고 24시간(時間) 후(後)가 40.

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GABA-enriched fermented Laminaria japonica improves cognitive impairment and neuroplasticity in scopolamine- and ethanol-induced dementia model mice

  • Reid, Storm N.S.;Ryu, Je-kwang;Kim, Yunsook;Jeon, Byeong Hwan
    • Nutrition Research and Practice
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    • 제12권3호
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    • pp.199-207
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    • 2018
  • BACKGROUND/OBJECTIVES: Fermented Laminaria japonica (FL), a type sea tangle used as a functional food ingredient, has been reported to possess cognitive improving properties that may aid in the treatment of common neurodegenerative disorders, such as dementia. MATERIALS/METHODS: We examined the effects of FL on scopolamine (Sco)- and ethanol (EtOH)-induced hippocampus-dependent memory impairment, using the Passive avoidance (PA) and Morris water maze (MWM) tests. To examine the underlying mechanisms associated with neuroprotective effects, we analyzed acetylcholine (ACh) and acetylcholinesterase (AChE) activity, brain tissue expression of muscarinic acetylcholine receptor (mAChR), cAMP response element binding protein (CREB) and extracellular signal-regulated kinases 1/2 (ERK1/2), and immunohistochemical analysis, in the hippocampus of mice, compared to current drug therapy intervention. Biochemical blood analysis was carried out to determine the effects of FL on alanine transaminase (ALT), aspartate transaminase (AST), and triglyceride (TG) and total cholesterol (TC) levels. 7 groups (n = 10) consisted of a control (CON), 3 Sco-induced dementia and 3 EtOH-induced dementia groups, with both dementia group types containing an untreated group (Sco and EtOH); a positive control, orally administered donepezil (Dpz) (4mg/kg) (Sco + Dpz and EtOH + Dpz); and an FL (50 mg/kg) treatment group (Sco + FL50 and EtOH + FL50), orally administered over the 4-week experimental period. RESULTS: FL50 significantly reduced EtOH-induced increase in AST and ALT levels. FL50 treatment reduced EtOH-impaired step-through latency time in the PA test, and Sco- and EtOH-induced dementia escape latency times in the MWM test. Moreover, anticholinergic effects of Sco and EtOH on the brain were reversed by FL50, through the attenuation of AChE activity and elevation of ACh concentration. FL50 elevated ERK1/2 protein expression and increased p-CREB (ser133) in hippocampus brain tissue, according to Western blot and immunohistochemistry analysis, respectively. CONCLUSION: Overall, these results suggest that FL may be considered an efficacious intervention for Sco- and EtOH-induced dementia, in terms of reversing cognitive impairment and neuroplastic dysfunction.

돼지 적출 심장 관상동맥에 있어서 Perivascular Nerve Stimulation에 의한 Cholinergic 수축 작용 (Cholinergic Contraction to the Perivascular Nerve Stimulation on the Isolated Coronary Artery of Pig)

  • 이한기;구봉오;문상은;심철수
    • The Journal of Korean Physical Therapy
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    • 제13권1호
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    • pp.61-71
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    • 2001
  • The purpose oi this study is to identify clearly the physiologic significance of autonomic nervous system. This study is to find the loose of endogenous neurotransmitter while using the neural response of the neural excitatory action which is distributed to the perivascular smooth muscle through the electrical stimulation of the smooth muscle of coronary artery of pig. The effects of perivascular nerve stimulation were investigated on isolated coronary artery of pig.1 . The magnitude of contractile response to perivascular nerve stimulation increased with increasing frequency (2-80 Hz) of stimulation. 2. The contractions to perivascular nerve stimulation(40V, 40Hz. 0.5msec, 1 min) were increased greatly by pretreatment of the cholinestrase inhibitor physostigmine. 3. The contraction to perivascular nerve stimulation(40V,40Hz, 0.5msec, 1min) was antagonised markedly by the muscarinic antagonist atropine. 4. The contraction to perivascular nerve stimulation(40V, 40Hz, 0.5msec, 1 min) was blocked by the neural blocker tetrodotoxin. 5. The contractions to perivascular nerve stimulation(40V. 40Hz, 0.5msec, 1 min) were not affected significantly by the -adrenergic antagonist phentolamine or - adrenergic antagonist propranolol. 6. The contractile response by the acetylcholine was increased by the pretreatment of cholinestrase inhibitor physostigmine. The finding suggest that it is powerful excitatory action linked to muscarinic receptor by cholinergic nerve in coronary artery of pig.

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Influence of Total Ginseng Saponin on Catecholamine Secretion Evoked by Nicotinic Receptor Stimulation in the Perfused Rat Adrenal Gland

  • Lim Dong-Yoon;Kil Young-Woo
    • 고려인삼학회:학술대회논문집
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    • 고려인삼학회 2002년도 학술대회지
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    • pp.401-415
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    • 2002
  • Lim and his coworkers (1987; 1988; 1989) have also found that all of total Ginseng saponin, panaxadiol-and panaxatriol-type saponins cause the increased secretion of catecholamines (CA) in a $Ca^{2+}$ -dependent fashion from the isolated perfused rabbit adrenal glands through the activation of cholinergic (both nicotinic and muscarinic) receptors. These CA secretory effects are partly due to the direct action on the rabbit adrenomedullary chromaffin cells. However, the present study was designed to examine the effect of total ginseng saponin on CA secretion evoked by activation of cholinergic nicotinic receptors in the isolated perfused model of the rat adrenal gland. Total ginseng saponin given (100 ${\mu}g$/20 min) into an adrenal vein did fail to produce alteration of spontaneous CA release from the rat adrenal medulla. Acetylcholine(5.32 mM)- and DMPP(100 ${\mu}M$, a selective nicotinic receptor agonist)-evoked CA secretory responses were reduced markedly after the pretreatment with the total ginseng saponin at a rate of 100 ${\mu}g$/6.2 ml/20 min, respectively. Pretreatment with total ginseng saponin also depressed greatly high potassium (56 mM, a membrane depolarizing agent)- and Bay-K-8644 (10 ${\mu}M$, a calcium channel activator)-induced CA secretions. Taken together, it is thought that total ginseng saponin can inhibit the releasing effect of CA evoked by nicotinic receptor stimulation from the isolated perfused rat adrenal medulla, which seems to be associated to the direct inhibition of influx through L-type calcium channel into the rat adrenomedullary chromaffin cells. It seems that there is species differences in the adrenomedullary catecholamine secretion between the rabbit and rat.

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이스라엘잉어 장관 수축에 관여하는 약물수용체에 관한 연구 (Characterization of the drug receptors responsible for intestinal contraction in Israeli carp)

  • 윤효인;한경호;박승춘;조준형;오태광
    • 대한수의학회지
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    • 제34권3호
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    • pp.447-456
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    • 1994
  • In order to elucidate the characterization of receptors involved in inestinal motility of Israeli carp, spontaneously contracting Israeli carp intestinal preperations were prepared and mounted in the organ chambers for contraction traicings using a polygraph. Various contractile agonists were treated and their dose-response curves were constructed. $EC_{50}$ values$(pD_2)$ of each agonist on specific receptors, $pA_2$ values of competitive antagonists against some agonists, and $K_1$, values of noncompetitive antagonists against some agonists were analyzed for characterization of receptors related with the intestinal contraction. Results obtained through the experiments were summarized as follows: 1. Acetylcholine(ACh) exhibited biphasic dose-response curves: initial ACh-induced dose dependent contractions were observed in pM levels but followed by decreased response in in-between concentration levels. Dose dependent contractions reappeared in ${\mu}M$ level. The peaks in pM and ${\mu}M$ levels appeared in $10^{-13}M$ and $3{\times}10^{-5}M$, respectvely. 2. Carbachol(CaCh) exhibited dose dependent contractions from $10^{-9}M$ to $10^{-5}M$, and its $pD_2$ values were higher than those of ACh($5.60{\pm}0.11$). ACh and CaCh exhibited equiactive contractions. Nicotine had no effects on contractile responses of Israeli carp intestine. 3. ACh-induced responses were inhibited by atropine($K_1:7{\times}10^{-8}M$), a muscarinic antagonist, in a non-competitive manner. But CaCh-induced responses were inhibited by both antimuscarinic atropine($pA_2:9.52{\pm}0.14$) and selective $M_2$ antagonistic 4-DAMP($pA_2:8.16{\pm}0.09$), in competitive manners. Nicotine receptor antagonistic decamethonium and hexamethonium had no effects on ACh-and CaCh-induced contractions. Therefore, the cholinergic receptor related to intestinal motility of Israeli carp was assumed as $M_2$ type. 4. In Israeli carp intestine, 5-HT (serotonin) exhibited dose dependent contractions in concentration range from $10^{-8}M$ to $10^{-5}M$. The maximal responses, however, were corresponded to about 50% of those of ACh or CaCh. 5-HT induced contractions were inhibited by $5-HT_2$ antagonistic ketanserin ($K_1: 7.8{\times}10^{-4}M$) in a non-competitive manner, but not by both of anti $5-HT_1$, spiperone and anti $5-HT_3$, MDL-72222. Hence, $5-HT_2$ receptors are suggested to be existed in Isreli carp intestine.

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Inhibitory Effects of Total Ginseng Saponin on Catecholamine Secretion from the Perfused Adrenal Medulla of SHRs

  • Jang, Seok-Jeong;Lim, Hyo-Jeong;Lim, Dong-Yoon
    • Journal of Ginseng Research
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    • 제35권2호
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    • pp.176-190
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    • 2011
  • There seems to be some controversy about the effect of total ginseng saponin (TGS) on the secretion of catecholamines (CA) from the adrenal gland. Therefore, the present study aimed to determine whether TGS can affect the CA release in the perfused model of the adrenal medulla isolated from spontaneously hypertensive rats (SHRs). TGS (15-150 ${\mu}g/mL$), perfused into an adrenal vein for 90 min, inhibited the CA secretory responses evoked by acetylcholine (ACh, 5.32 mM) and high $K^+$ (56 mM, a direct membrane depolarizer) in a dose- and time-dependent fashion. TGS (50 ${\mu}g/mL$) also time-dependently inhibited the CA secretion evoked by 1.1-dimethyl-4 -phenyl piperazinium iodide (DMPP; 100 ${\mu}M$, a selective neuronal nicotinic receptor agonist) and McN-A-343 (100 ${\mu}M$, a selective muscarinic M1 receptor agonist). TGS itself did not affect basal CA secretion (data not shown). Also, in the presence of TGS (50 ${\mu}g/mL$), the secretory responses of CA evoked by veratridine (a selective $Na^+$ channel activator (50 ${\mu}M$), Bay-K-8644 (an L-type dihydropyridine $Ca^{2+}$ channel activator, 10 ${\mu}M$), and cyclopiazonic acid (a cytoplasmic $Ca^{2+}$-ATPase inhibitor, 10 ${\mu}M$) were significantly reduced, respectively. Interestingly, in the simultaneous presence of TGS (50 ${\mu}g/mL$) and N${\omega}$-nitro-L-arginine methyl ester hydrochloride [an inhibitor of nitric oxide (NO) synthase, 30 ${\mu}M$], the inhibitory responses of TGS on the CA secretion evoked by ACh, high $K^+$, DMPP, McN-A-343, Bay-K-8644, cyclopiazonic acid, and veratridine were considerably recovered to the extent of the corresponding control secretion compared with the inhibitory effect of TGS-treatment alone. Practically, the level of NO released from adrenal medulla after the treatment of TGS (150 ${\mu}g/mL$) was greatly elevated compared to the corresponding basal released level. Taken together, these results demonstrate that TGS inhibits the CA secretory responses evoked by stimulation of cholinergic (both muscarinic and nicotinic) receptors as well as by direct membrane-depolarization from the isolated perfused adrenal medulla of the SHRs. It seems that this inhibitory effect of TGS is mediated by inhibiting both the influx of $Ca^{2+}$ and Na+ into the adrenomedullary chromaffin cells and also by suppressing the release of $Ca^{2+}$ from the cytoplasmic calcium store, at least partly through the increased NO production due to the activation of nitric oxide synthase, which is relevant to neuronal nicotinic receptor blockade, without the enhancement effect on the CA release. Based on these effects, it is also thought that there are some species differences in the adrenomedullary CA secretion between the rabbit and SHR.

Economical Sweating Function in Africans: Quantitative Sudomotor Axon Reflex Test

  • Lee, Jeong-Beom;Bae, Jun-Sang;Choi, Jeong-Hwan;Ham, Joo-Hyun;Min, Young-Ki;Yang, Hun-Mo;Kazuhiro, Shimizu;Matsumoto, Takaaki
    • The Korean Journal of Physiology and Pharmacology
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    • 제8권1호
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    • pp.21-25
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    • 2004
  • People in tropics have the ability to tolerate heat by residential permanence in the tropics. Previously, we have shown that African and Thai subjects who lived for whole their lives in only their respective countries sweat less under hot conditions than South Koreans who also lived whole their lives in Korea. The difference in sweating responses was attributed to the dissimilar central and peripheral sweating mechanisms operating in people from both groups. In the present study, acetylcholine (ACh), the primary transmitter for the sudomotor functions, was iontophoretically administered to South Koreans and Africans to determine the characteristic sudorific responses of their acclimatized biologic make-up to their respective environments. Using quantitative sudomotor axon reflex test (QSART), direct (DIR) and axon reflex (AXR) responses were evaluated. The findings revealed that the sweat onset-time among South Koreans was 0.91 min earlier than among Africans (P<0.01). The axon reflex sweat volume of nicotine receptor activity AXR(1) and sweat volume of muscarinic receptor activity DIR(2) among South Koreans were 79% and 53% greater (P<0.01), respectively. These results indicate that the reduced thermal sweating among Africans is at least in part attributed to the diminished sensitivity of sweat glands to ACh.

Modulatory Effect of the Tyrosine Kinase and Tyrosine Phosphatase on the ACh-activated $K^{+}$ Channel in Adult Rat Atrial Cells

  • Chang, Kyeong-Jae;Rhie, Sang-Ho;Heo, Ilo;Kim, Yang-Mi;Haan, Jae-Hee;Hong, Seong-Geun
    • The Korean Journal of Physiology
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    • 제30권2호
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    • pp.209-218
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    • 1996
  • Acetylcholine (ACh) activates the inwardly rectifying muscarinic $K^{+}$ channel in rat atrial cells via pertussis toxin (PTX)-sensitive G-protein ($G_k$) coupled with the muscarinic receptor (mAChR). Although this $K^{+}\;(K_{ACh})$ channel function has reported to be modulated by the phosphorylation process, a kinase and phosphatase involved in these processes are still unclear. Since either PKA or PKC was not effective on this ATP-modulation, the present study examined the possible involvement of the protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP) in the function of the $K_{ACh}$ Channel. In the inside-out (I/O) patch preparation excised from the adult rat atrial cell, when activated by 10 ${\mu}M$ ACh in the pipette and 100 ${\mu}M$ GTP in the bath, the mean open time (${\tau}_{o}$) and the channel activity ($K_{ACh}$) was 1.13 ms (n=5) and 0.19 (n=6), respectively. Following the application of 1 mM ATP into the bath, ${\tau}_{o}$ increased by 34% (1.54 ms, n=5) and $K_{ACh}$ by 66% (0.28, n=6). Channel function elevated by ATP was lasted after washout of ATP. However, this ATP-induced increase in the $K_{ACh}$ channel function did not occur in pretreated cells with genistein ($50{\sim}100 {\mu}M$), a selective PTK inhibitor, but occurred in pretreated cells with equimolar daidzein, a negative control of the genistein. On the contrary, PTP which acts on tyrosine residue conversely reversed both ATP-induced increased ${\tau}_{o}$ by 32% (1.20 ms, n=3) and $K_{ACh}$ by 41% (0.15, n=3), respectively. Taken together, these results suggest that $K_{ACh}$ channel may, at least partly, be regulated by the tyrosyl phosphorylation, although it is unclear where this process exerts on the muscarinic signal transduction pathway comprising the mAChR-$G_{k}$-the $K_{ACh}$ channel.

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G Protein-Coupled Receptor Signaling in Gastrointestinal Smooth Muscle

  • Sohn, Uy-Dong;Kim, Dong-Seok;Murthy, Karnam S.
    • The Korean Journal of Physiology and Pharmacology
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    • 제5권4호
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    • pp.287-297
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    • 2001
  • Contraction of smooth muscle is initiated by an increase in cytosolic $Ca^{2+}$ leading to activation of $Ca^{2+}$/ calmodulin-dependnet myosin light chain (MLC) kinase and phosphorylation of MLC. The types of contraction and signaling mechanisms mediating contraction differ depending on the region. The involvement of these different mechanisms varies depending on the source of $Ca^{2+}$ and the kinetic of $Ca^{2+}$ mobilization. $Ca^{2+}$ mobilizing agonists stimulate different phospholipases $(PLC-{\beta},\;PLD\;and\;PLA_2)$ to generate one or more $Ca^{2+}$ mobilizing messengers $(IP_3\;and\;AA),$ and diacylglycerol (DAG), an activator of protein kinase C (PKC). The relative contributions of $PLC-{\beta},\;PLA_2$ and PLD to generate second messengers vary greatly between cells and types of contraction. In smooth muscle cell derived form the circular muscle layer of the intestine, preferential hydrolysis of $PIP_2$ and generation of $IP_3$ and $IP_3-dependent\;Ca^{2+}$ release initiate the contraction. In smooth muscle cells derived from longitudinal muscle layer of the intestine, preferential hydrolysis of PC by PLA2, generation of AA and AA-mediated $Ca^{2+}$ influx, cADP ribose formation and $Ca^{2+}-induced\;Ca^{2+}$ release initiate the contraction. Sustained contraction, however, in both cell types is mediated by $Ca^{2+}-independent$ mechanism involving activation of $PKC-{\varepsilon}$ by DAG derived form PLD. A functional linkage between $G_{13},$ RhoA, ROCK, $PKC-{\varepsilon},$ CPI-17 and MLC phosphorylation in sustained contraction has been implicated. Contraction of normal esophageal circular muscle (ESO) in response to acetylcholine (ACh) is linked to $M_2$ muscarinic receptors activating at least three intracellular phospholipases, i.e. phosphatidylcholine-specific phospholipase C (PC-PLC), phospholipase D (PLD) and the high molecular weight (85 kDa) cytosolic phospholipase $A_2\;(cPLA_2)$ to induce phosphatidylcholine (PC) metabolism, production of diacylglycerol (DAG) and arachidonic acid (AA), resulting in activation of a protein kinase C (PKC)-dependent pathway. In contrast, lower esophageal sphincter (LES) contraction induced by maximally effective doses of ACh is mediated by muscarinic $M_3$ receptors, linked to pertussis toxin-insensitive GTP-binding proteins of the $G_{q/11}$ type. They activate phospholipase C, which hydrolyzes phosphatidylinositol bisphosphate $(PIP_2),$ producing inositol 1, 4, 5-trisphosphate $(IP_3)$ and DAG. $IP_3$ causes release of intracellular $Ca^{2+}$ and formation of a $Ca^{2+}$-calmodulin complex, resulting in activation of myosin light chain kinase and contraction through a calmodulin-dependent pathway.

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