1
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Filogonio R, Sartori MR, Morgensen S, Tavares D, Campos R, Abe AS, Taylor EW, Rodrigues GJ, De Nucci G, Simonsen U, Leite CAC, Wang T. Cholinergic regulation along the pulmonary arterial tree of the South American rattlesnake: vascular reactivity, muscarinic receptors, and vagal innervation. Am J Physiol Regul Integr Comp Physiol 2020; 319:R156-R170. [DOI: 10.1152/ajpregu.00310.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Vascular tone in the reptilian pulmonary vasculature is primarily under cholinergic, muscarinic control exerted via the vagus nerve. This control has been ascribed to a sphincter located at the arterial outflow, but we speculated whether the vascular control in the pulmonary artery is more widespread, such that responses to acetylcholine and electrical stimulation, as well as the expression of muscarinic receptors, are prevalent along its length. Working on the South American rattlesnake ( Crotalus durissus), we studied four different portions of the pulmonary artery (truncus, proximal, distal, and branches). Acetylcholine elicited robust vasoconstriction in the proximal, distal, and branch portions, but the truncus vasodilated. Electrical field stimulation (EFS) caused contractions in all segments, an effect partially blocked by atropine. We identified all five subtypes of muscarinic receptors (M1–M5). The expression of the M1 receptor was largest in the distal end and branches of the pulmonary artery, whereas expression of the muscarinic M3 receptor was markedly larger in the truncus of the pulmonary artery. Application of the neural tracer 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindo-carbocyanine perchlorate (DiI) revealed widespread innervation along the whole pulmonary artery, and retrograde transport of the same tracer indicated two separate locations in the brainstem providing vagal innervation of the pulmonary artery, the medial dorsal motor nucleus of the vagus and a ventro-lateral location, possibly constituting a nucleus ambiguus. These results revealed parasympathetic innervation of a large portion of the pulmonary artery, which is responsible for regulation of vascular conductance in C. durissus, and implied its integration with cardiorespiratory control.
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Affiliation(s)
- Renato Filogonio
- Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Marina R. Sartori
- Department of Zoology, State University of São Paulo, Rio Claro, São Paulo, Brazil
| | - Susie Morgensen
- Department of Biomedicine, Pulmonary, and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Driele Tavares
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Rafael Campos
- Superior Institute of Biomedical Sciences, Ceará State University, Fortaleza, Brazil
| | - Augusto S. Abe
- Department of Zoology, State University of São Paulo, Rio Claro, São Paulo, Brazil
| | - Edwin W. Taylor
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Gerson J. Rodrigues
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Gilberto De Nucci
- Faculty of Medical Sciences, Department of Pharmacology, University of Campinas, Campinas, Brazil
| | - Ulf Simonsen
- Department of Biomedicine, Pulmonary, and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Cléo A. C. Leite
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
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2
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Desgrouas C, Taudon N, Bun SS, Baghdikian B, Bory S, Parzy D, Ollivier E. Ethnobotany, phytochemistry and pharmacology of Stephania rotunda Lour. JOURNAL OF ETHNOPHARMACOLOGY 2014; 154:537-563. [PMID: 24768769 DOI: 10.1016/j.jep.2014.04.024] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 06/03/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Stephania rotunda Lour. (Menispermaceae) is an important traditional medicinal plant that is grown in Southeast Asia. The stems, leaves, and tubers have been used in the Cambodian, Lao, Indian and Vietnamese folk medicine systems for years to treat a wide range of ailments, including asthma, headache, fever, and diarrhoea. AIM OF THE REVIEW To provide an up-to-date, comprehensive overview and analysis of the ethnobotany, phytochemistry, and pharmacology of Stephania rotunda for its potential benefits in human health, as well as to assess the scientific evidence of traditional use and provide a basis for future research directions. MATERIAL AND METHODS Peer-reviewed articles on Stephania rotunda were acquired via an electronic search of the major scientific databases (Pubmed, Google Scholar, and ScienceDirect). Data were collected from scientific journals, theses, and books. RESULTS The traditional uses of Stephania rotunda were recorded in countries throughout Southeast Asia (Cambodia, Vietnam, Laos, and India). Different parts of Stephania rotunda were used in traditional medicine to treat about twenty health disorders. Phytochemical analyses identified forty alkaloids. The roots primarily contain l-tetrahydropalmatine (l-THP), whereas the tubers contain cepharanthine and xylopinine. Furthermore, the chemical composition differs from one region to another and according to the harvest period. The alkaloids exhibited approximately ten different pharmacological activities. The main pharmacological activities of Stephania rotunda alkaloids are antiplasmodial, anticancer, and immunomodulatory effects. Sinomenine, cepharanthine, and l-stepholidine are the most promising components and have been tested in humans. The pharmacokinetic parameters have been studied for seven compounds, including the three most promising compounds. The toxicity has been evaluated for liriodenine, roemerine, cycleanine, l-tetrahydropalmatine, and oxostephanine. CONCLUSION Stephania rotunda is traditionally used for the treatment of a wide range of ailments. Pharmacological investigations have validated different uses of Stephania rotunda in folk medicine. The present review highlights the three most promising compounds of Stephania rotunda, which could constitute potential leads in various medicinal fields, including malaria and cancer.
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Affiliation(s)
- Camille Desgrouas
- UMR-MD3, IRBA, Faculté de Pharmacie, 27 boulevard Jean Moulin CS30064 13385 Marseille cedex 5, Aix-Marseille Université, France; UMR-MD3, Laboratoire de Pharmacognosie et Ethnopharmacologie, Faculté de Pharmacie, 27 boulevard Jean Moulin CS30064 13385 Marseille cedex 5, Aix-Marseille Université, France.
| | | | - Sok-Siya Bun
- UMR-MD3, Laboratoire de Pharmacognosie et Ethnopharmacologie, Faculté de Pharmacie, 27 boulevard Jean Moulin CS30064 13385 Marseille cedex 5, Aix-Marseille Université, France.
| | - Beatrice Baghdikian
- UMR-MD3, Laboratoire de Pharmacognosie et Ethnopharmacologie, Faculté de Pharmacie, 27 boulevard Jean Moulin CS30064 13385 Marseille cedex 5, Aix-Marseille Université, France.
| | - Sothavireak Bory
- Faculté de Pharmacie, Université des Sciences de la Santé, no. 73, Monivong Blvd, Daun Penh, Phnom Penh, Cambodia.
| | - Daniel Parzy
- UMR-MD3, IRBA, Faculté de Pharmacie, 27 boulevard Jean Moulin CS30064 13385 Marseille cedex 5, Aix-Marseille Université, France.
| | - Evelyne Ollivier
- UMR-MD3, Laboratoire de Pharmacognosie et Ethnopharmacologie, Faculté de Pharmacie, 27 boulevard Jean Moulin CS30064 13385 Marseille cedex 5, Aix-Marseille Université, France.
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3
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Vasorelaxant effect of FR900359 from Ardisia crenata on rat aortic artery. J Nat Med 2012; 67:196-201. [DOI: 10.1007/s11418-012-0644-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 02/10/2012] [Indexed: 11/26/2022]
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4
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Zaima K, Koga I, Iwasawa N, Hosoya T, Hirasawa Y, Kaneda T, Ismail IS, Lajis NH, Morita H. Vasorelaxant activity of indole alkaloids from Tabernaemontana dichotoma. J Nat Med 2012; 67:9-16. [PMID: 22350216 DOI: 10.1007/s11418-012-0638-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 01/25/2012] [Indexed: 12/11/2022]
Abstract
The aim of this study was to search for bioactive natural products from medicinal plants targeting vasorelaxant activity and we found the methanol extract from bark of Tabernaemontana dichotoma showed vasorelaxant activity on rat aorta. We isolated eight indole alkaloids including 10-methoxyalstonerine (1), a new macroline type indole alkaloid, from bark of T. dichotoma. These were respectively identified as 10-methoxyaffinisine (2), lochnerine (3), cathafoline (4), (-)-alstonerine (5), 19,20-dehydro-10-methoxytalcarpine (6), alstonisine (7), and alstonal (8) based on spectroscopic analysis. Among them, sarpagine type (2 and 3), akuammiline type (4), and macroline oxindole type (7 and 8) showed potent vasorelaxant activity. Mechanism of action on vasorelaxant activity of 10-methoxyaffinisine (2), cathafoline (4), and alstonisine (7) was clarified. Effects of 10-methoxyaffinisine (2), cathafoline (4), and alstonisine (7) were partially mediated the NO release from endothelial cells. Furthermore, 10-methoxyaffinisine (2) and alstonisine (7) attribute to the inhibitory effect of VDC and ROC, and cathafoline (4) have inhibitory effect on Ca(2+) influx via ROC. In addition, 10-methoxyaffinisine (2) as a major compound from bark of T. dichotoma showed hypotensive effect on normotensive rats in vivo.
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Affiliation(s)
- Kazumasa Zaima
- Faculty of Pharmaceutical Sciences, Hoshi University, Shinagawa-ku, Tokyo, Japan
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5
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ZP120 causes relaxation by pre-junctional inhibition of noradrenergic neurotransmission in rat mesenteric resistance arteries. Br J Pharmacol 2008; 153:1185-94. [PMID: 18193068 DOI: 10.1038/sj.bjp.0707688] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE ZP120 (Ac-RYYRWKKKKKKK-NH(2)), is a new partial nociceptin/orphanin FQ (NOP) receptor agonist with sodium-potassium sparing aquaretic effects. The mechanisms of vasodilatation of ZP120 were examined in rat mesenteric resistance arteries. EXPERIMENTAL APPROACH Arterial segments (internal diameters 206+/-4 microm, n=224) were mounted in microvascular myographs for isometric tension recordings and electrical field stimulation (EFS). KEY RESULTS ZP120 and the endogenous NOP receptor ligand, N/OFQ, did not relax arteries contracted with noradrenaline or adenosine-triphosphate. EFS-evoked contractions were inhibited by a purinoceptor antagonist, suramin, and the alpha(1)-adrenoceptor antagonist prazosin. N/OFQ inhibited, concentration-dependently, EFS-evoked contractions with a maximal effect of 52+/-3% (n=8) at 1 microM. The maximal effect of 1 microM ZP120 was lower (27+/-5%, P<0.05, n=9) than for N/OFQ. Endothelial removal or pretreatment with capsaicin did not influence the vasodilator effects of ZP120 and N/OFQ. ZP120 and N/OFQ responses were preserved in the presence of suramin. The alpha(2)-adrenoceptor antagonist, rauwolscine, antagonized the effect of clonidine and brimonidine, but ZP120 and N/OFQ inhibition of EFS-evoked contraction was unaltered. The competitive NOP receptor antagonist, UFP-101 (10 microM), prevented the inhibitory effect of N/OFQ, but not ZP120 suggesting that N/OFQ and ZP120 have distinct modes of interaction with the NOP receptor. CONCLUSIONS AND IMPLICATIONS Our findings suggest that the vasodilator effect of ZP120 and N/OFQ in rat mesenteric resistance arteries is mediated by prejunctional inhibition of adrenergic neurotransmission. These properties, that promote diuresis and attenuate the cardiovascular consequences of increased sympathetic nerve activity, make ZP120 a promising drug candidate.
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6
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Yang K, Jin G, Wu J. The neuropharmacology of (-)-stepholidine and its potential applications. Curr Neuropharmacol 2007; 5:289-94. [PMID: 19305745 PMCID: PMC2644490 DOI: 10.2174/157015907782793649] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2007] [Revised: 03/30/2007] [Accepted: 05/29/2007] [Indexed: 01/25/2023] Open
Abstract
(-)-Stepholidine (SPD), a natural product isolated from the Chinese herb Stephania, possesses dopamine (DA) D1 partial agonistic and D2 antagonistic properties in the nigrostriatal and mesocorticolimbic DAergic pathways. These unique dual effects have suggested that SPD can effectively restore previously imbalanced functional linkage between D1 and D2 receptors under schizophrenic conditions, in which, SPD improves both the negative and positive symptoms of schizophrenia. SPD also relieves the motor symptoms of Parkinson's disease (PD) when co-administered with Levodopa. Furthermore, SPD exhibits neuroprotective effects through an antioxidative mechanism and slows down the progression of neuronal degeneration in the substantia nigra (SN) of PD patients and/or animal models. Therefore, SPD is a novel, natural compound with potentially therapeutic roles in the treatment of schizophrenia and/or PD.
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Affiliation(s)
- Kechun Yang
- Division of Neurology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA
- Department of Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Guozhang Jin
- Department of Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institute of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jie Wu
- Division of Neurology, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, AZ 85013, USA
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7
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Neurotoxins and medicinals for the treatment of Parkinson’s disease. Part 2: dopamine receptors and their agonists. Pharm Chem J 2005. [DOI: 10.1007/s11094-006-0014-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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8
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Mo YQ, Jin XL, Chen YT, Jin GZ, Shi WX. Effects of l-stepholidine on forebrain Fos expression: comparison with clozapine and haloperidol. Neuropsychopharmacology 2005; 30:261-7. [PMID: 15578005 DOI: 10.1038/sj.npp.1300628] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
l-Stepholidine (SPD) is a tetrahydroprotoberberine alkaloid and a mixed dopamine D1 agonist/D2 antagonist. Preliminary clinical trials suggest that SPD improves both positive and negative symptoms of schizophrenia without producing significant extrapyramidal side effects. Here, we report that SPD mimics the effect of the atypical antipsychotic drug clozapine, preferentially increasing Fos expression in corticolimbic areas. Thus, at 10 mg/kg (i.p.), SPD induced Fos expression in the medial prefrontal cortex (mPFC), nucleus accumbens (NAc), and lateral septal nucleus (LSN) without significantly affecting the dorsolateral striatum (DLSt). At higher doses (20-40 mg/kg), SPD also increased Fos expression in the DLSt. The increase, however, was less pronounced than the increase seen in the NAc. Within the NAc, SPD also induced more Fos expression in the shell than in the core. In all subcortical areas examined, the Fos expression induced by SPD was mimicked by the D2 antagonist sulpiride and reversed by the D2 agonist quinpirole, suggesting that the effect is due to blockade of D2-like receptors by SPD. In the mPFC, however, the effect was not mimicked by sulpride or reversed by quinpirole. It was also not mimicked by the D1 agonist SKF38393 or SKF38393 plus sulpride, and not reversed by the D1 antagonist SCH23390. These results suggest that, in the mPFC, SPD may induce Fos expression through a non-DA mechanism. Whether the mechanism involves an interaction of SPD with other neurotransmitters such as 5-HT and norepinephrine remains to be determined.
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Affiliation(s)
- Yi-Qing Mo
- Department of Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
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9
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Glavind-Kristensen M, Matchkov V, Hansen VB, Forman A, Nilsson H, Aalkjaer C. KATP-channel-induced vasodilation is modulated by the Na,K-pump activity in rabbit coronary small arteries. Br J Pharmacol 2004; 143:872-80. [PMID: 15504751 PMCID: PMC1575946 DOI: 10.1038/sj.bjp.0706016] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The purpose of the study was to evaluate the importance of the Na,K-pump in relaxations induced by K(ATP)-channel openers in rabbit coronary small arteries. Arterial segments were mounted in myographs for recording of isometric tension. Whole-cell patch clamp was used to assess K(ATP)-channel currents in isolated smooth muscle cells from the arteries. In arteries preconstricted with the thromboxane A(2) analogue U46619 pinacidil and cromakalim induced concentration-dependent relaxations. In arteries preconstricted with potassium (124 mM) only high concentrations of pinacidil had a small relaxant effect. In arteries preconstricted with U46619 pinacidil-induced relaxations were unaffected by pretreatment with N(omega)-nitro-L-arginine (L-NNA) and only slightly reduced after mechanical removal of the endothelium. Pinacidil induced relaxations were not significantly affected by 1 microM glibenclamide. However, the relaxations were partly inhibited in potassium-free media and by 1 microM ouabain. In contrast, the concentration-dependent relaxation to cromakalim was partly blocked by 1 microM glibenclamide and partly by 1 microM ouabain and when both drugs were present the inhibition increased. Ouabain (1 microM) and glibenclamide (1 microM) each partly inhibited an ATP-sensitive current induced by pinacidil and cromakalim. In the presence of both inhibitors a greater inhibition was seen. When the solution in the patch pipette was sodium-free the current was reduced and ouabain had no effect. The study suggests that the relaxation to cromakalim and most likely pinacidil is mediated through opening of K(ATP) channels. Inhibition of the Na,K-pump, however, may change the local environment for the K(ATP) channels (i.e. increases the ATP/ADPratio and/or decreases the transmembrane potassium gradient), which partly prevents the activation of the K(ATP)-channel current.
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Affiliation(s)
- Marianne Glavind-Kristensen
- Research Laboratory, Department of Obstetrics and Gynecology, Aarhus University Hospital, 8200 Aarhus, Denmark.
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10
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Zeng C, Wang D, Yang Z, Wang Z, Asico LD, Wilcox CS, Eisner GM, Welch WJ, Felder RA, Jose PA. Dopamine D
1
Receptor Augmentation of D
3
Receptor Action in Rat Aortic or Mesenteric Vascular Smooth Muscles. Hypertension 2004; 43:673-9. [PMID: 14769810 DOI: 10.1161/01.hyp.0000118958.27649.6f] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dopamine is an important modulator of blood pressure, in part, by regulating vascular resistance. To test the hypothesis that D
1
and D
3
receptors interact in vascular smooth muscle cells, we studied A10 cells, a rat aortic smooth muscle cell line, and rat mesenteric arteries that express both dopamine receptor subtypes. Fenoldopam, a D
1
-like receptor agonist, increased both D
1
and D
3
receptor protein in a time-dependent and a concentration-dependent manner in A10 cells. The effect of fenoldopam was specific because a D
1
-like receptor antagonist, SCH23390 (10
−7
M/24 h), completely blocked the stimulatory effect of fenoldopam (10
−7
M/24 h) (D
3
receptor: control=21±1 density units [DU]); SCH23390=23±2 DU; fenoldopam=33±2 DU; fenoldopam+SCH23390=23±2 DU; n=10). D
1
and D
3
receptors physically interacted with each other because fenoldopam (10
−7
M/24 h) increased D
1
/D
3
receptor coimmunoprecipitation (35±5 versus 65±5 DU; n=8). A D
3
receptor agonist, PD128907, relaxed mesenteric arterial rings independent of the endothelium, effects that were blocked by a D
3
receptor antagonist, U99194A. Costimulation of D
1
and D
3
receptors led to additive vasorelaxation. We conclude that the D
1
receptor regulates the D
3
receptor by physical interaction and receptor expression. D
1
receptor stimulation augments D
3
receptor vasorelaxant effects. An interaction of D
1
and D
3
receptors may be involved in the regulation of blood pressure.
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MESH Headings
- Animals
- Antibody Specificity
- Aorta/cytology
- Cell Line
- Culture Techniques
- Dopamine Agonists/pharmacology
- Dopamine Antagonists/pharmacology
- Fenoldopam/pharmacology
- Male
- Mesenteric Arteries/anatomy & histology
- Mesenteric Arteries/chemistry
- Mesenteric Arteries/physiology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Rats
- Rats, Inbred WKY
- Receptors, Dopamine D1/agonists
- Receptors, Dopamine D1/immunology
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D2/agonists
- Receptors, Dopamine D2/immunology
- Receptors, Dopamine D2/metabolism
- Receptors, Dopamine D3
- Vasodilation/drug effects
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Affiliation(s)
- Chunyu Zeng
- Department of Pediatrics, PHC-2 Georgetown University Medical Center, 3800 Reservoir Road, NW, Washington, DC 20007, USA.
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11
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Kun A, Martinez AC, Tankó LB, Pataricza J, Papp JG, Simonsen U. Ca2+-activated K+ channels in the endothelial cell layer involved in modulation of neurogenic contractions in rat penile arteries. Eur J Pharmacol 2003; 474:103-15. [PMID: 12909201 DOI: 10.1016/s0014-2999(03)02004-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The present study was designed to investigate the functional K+ channels involved in contractions induced by electrical field stimulation in isolated rat penile arteries. Blockers of Ca2+-activated K+ channels (KCa), tetraethylammonium, and of large-conductance KCa channels, charybdotoxin and iberiotoxin, as well as a blocker of voltage-dependent K+ channels (KV), 4-aminopyridine, increased resting tension in penile small arteries. In the presence of propranolol and NG-nitro-L-arginine (L-NOARG), electrical field stimulation evoked prazosin-sensitive contractions. In endothelium-intact preparations, these latter contractions were enhanced in the presence of tetraethylammonium and charybdotoxin. However, these blockers did not enhance contractions evoked by exogenously added noradrenaline. Endothelial cell removal increased the neurogenic contractions but tetraethylammonium had no further potentiating effect in these preparations. In the presence of an inhibitor of cyclooxygenase, indomethacin, and inhibitor of nitric oxide (NO) synthase, L-NOARG, acetylcholine evoked relaxations, which were abolished in the presence of either tetraethylammonium or charybdotoxin. In phenylephrine-contracted arteries treated with guanethidine and atropine, electrical field stimulation evoked relaxations, which were partially inhibited by L-NOARG and tetraethylammonium, without any additive effect of these drugs. These observations suggest that both large-conductance KCa channels and KV channels sensitive to iberiotoxin/tetraethylammonium and 4-aminopyridine, respectively, are directly involved in the modulation of myogenic tone of rat penile arteries. Furthermore, activation of endothelial intermediate-conductance KCa channels sensitive to tetraethylammonium and charybdotoxin leads to release of a non-NO nonprostanoid factor, which inhibits release of the neurotransmitter, noradrenaline, but these channels do not appear to be involved in inhibition of contraction evoked by exogenously applied noradrenaline in rat penile arteries.
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Affiliation(s)
- Attila Kun
- Department of Pharmacology, University of Aarhus, 8000 Aarhus C, Denmark
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