201
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Volgin DV, Mackiewicz M, Kubin L. Alpha(1B) receptors are the main postsynaptic mediators of adrenergic excitation in brainstem motoneurons, a single-cell RT-PCR study. J Chem Neuroanat 2001; 22:157-66. [PMID: 11522438 DOI: 10.1016/s0891-0618(01)00124-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Norepinephrine (NE) is an important modulator of brainstem motoneurons. It is released at high levels during wakefulness, whereas its reduced release during sleep may contribute to motor suppression, including upper airway hypotonia. To identify the receptors that mediate postsynaptic effects of NE in brainstem motoneurons of juvenile and adult rats, we determined the pattern of adrenoceptor mRNA expression and co-expression in retrogradely labeled and acutely dissociated hypoglossal (XII) motoneurons (n=121) using single-cell, real-time reverse transcription-polymerase chain reaction (RT-PCR). The alpha(1B) receptor mRNA was present in most motoneurons (33/39 or 85%). The remaining six adrenoceptor mRNA species investigated were consistently present in micropunches of tissue extracted from the XII nucleus, but were either rarely expressed in individual motoneurons (alpha(1A) mRNA in 15%, alpha(1D) in 14%, alpha(2B/C) in 2% of cells) or absent (alpha(2A), beta(1) and beta(2)). When present, the alpha(1A) and alpha(1D) mRNAs were co-expressed with alpha(1B) mRNA. The adrenoceptor mRNA expression profiles in dissociated locus coeruleus and inferior olive neurons were significantly different. We conclude that postsynaptic effects of NE in XII motoneurons are primarily mediated by alpha(1B) receptors; the effects ascribed to alpha(2) and/or beta adrenoceptors may be exerted presynaptically.
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Affiliation(s)
- D V Volgin
- Department of Animal Biology 205ED/VET, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6046, USA
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202
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Affiliation(s)
- K Starke
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Freiburg, Germany
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203
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Rajamani K, Leong S, Lavelle A, Docherty JR. Prejunctional actions of methylenedioxymethamphetamine in vas deferens from wild-type and alpha(2A/D)-adrenoceptor knockout mice. Eur J Pharmacol 2001; 423:223-8. [PMID: 11448488 DOI: 10.1016/s0014-2999(01)01118-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Methylenedioxymethamphetamine (MDMA, 'ecstasy') has major agonist actions at prejunctional alpha(2A/D)-adrenoceptors in the rat. We wished to establish whether MDMA has potency at more than one subtype of alpha(2)-adrenoceptor, in line with affinity in ligand-binding studies. We have investigated the effects of MDMA in vas deferens from wild-type and from knockout mice lacking the alpha(2A/D)-adrenoceptor. The potency of the alpha(2)-adrenoceptor agonist xylazine at inhibiting stimulation-evoked contractions to a single stimulus in the presence of cocaine was significantly reduced in knockout (pD(2) of 8.27+/-0.07, -log M, n=4) as compared with wild-type mice (8.69+/-0.08, n=4, P<0.05), whereas potency of MDMA was unchanged (5.39+/-0.06, n=4 versus 5.38+/-0.06, n=6). Similar differences between xylazine and MDMA were seen for responses to stimulation at 10 Hz for 4 s. In studies of mouse atria pre-incubated with (3)H-noradrenaline, the stimulation-evoked release of tritium was inhibited to a similar extent by MDMA (10 microM) in tissues from wild-type and knockout mice. The prejunctional alpha(2A/D)-adrenoceptor is reported to be replaced by the alpha(2C)-adrenoceptor in this knockout mouse, so that we have evidence that suggests that MDMA has similar potencies at both subtypes in functional studies.
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MESH Headings
- Adrenergic Agents/pharmacology
- Adrenergic Uptake Inhibitors/pharmacology
- Adrenergic alpha-Agonists/pharmacology
- Animals
- Desipramine/pharmacology
- Dose-Response Relationship, Drug
- Electric Stimulation
- Female
- Genotype
- Heart Atria/drug effects
- Heart Atria/metabolism
- In Vitro Techniques
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Muscle Contraction/drug effects
- N-Methyl-3,4-methylenedioxyamphetamine/pharmacology
- Neuromuscular Junction/drug effects
- Nifedipine/pharmacology
- Norepinephrine/metabolism
- Oxymetazoline/pharmacology
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/physiology
- Tritium/metabolism
- Vas Deferens/drug effects
- Vas Deferens/physiology
- Vasodilator Agents/pharmacology
- Xylazine/pharmacology
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Affiliation(s)
- K Rajamani
- Department of Physiology, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
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204
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Barr CL, Wigg K, Zai G, Roberts W, Malone M, Schachar R, Tannock R, Kennedy JL. Attention-deficit hyperactivity disorder and the adrenergic receptors alpha 1C and alpha 2C. Mol Psychiatry 2001; 6:334-7. [PMID: 11326305 PMCID: PMC4833494 DOI: 10.1038/sj.mp.4000863] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2000] [Revised: 12/04/2000] [Accepted: 12/04/2000] [Indexed: 11/08/2022]
Abstract
The adrenergic system has been hypothesized to be involved in the etiology of attention-deficit hyperactivity disorder (ADHD) based on pharmacological interventions and animal models. Noradrenergic neurons are implicated in the modulation of vigilance, improvement of visual attention, initiation of adaptive response, learning and memory. In this study we tested the genes for two adrenergic receptors, alpha 1C (ADRA1C) located on chromosome 8p11.2, and alpha 2C (ADRA2C) located on chromosome 4p16, as genetic susceptibility factors in ADHD. For the adrenergic receptor alpha 1C we used a C to T polymorphism that results in a change of Cys to Arg at codon 492 for the linkage study. For the adrenergic receptor alpha 2C gene we examined a dinucleotide repeat polymorphism located approximately 6 kb from the gene. We examined these polymorphisms in a sample of 103 families ascertained through an ADHD proband. Using the transmission disequilibrium test, we did not observe biased transmission of any of the alleles of these polymorphisms. We conclude that the alleles at the polymorphisms tested in these two genes are not linked to the ADHD phenotype in this sample of families.
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Affiliation(s)
- C L Barr
- Department of Psychiatry, The Toronto Western Hospital, Toronto, Ontario, Canada.
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205
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Altobelli D, Martire M, Maurizi S, Preziosi P. Interaction of formamidine pesticides with the presynaptic alpha(2)-adrenoceptor regulating. Toxicol Appl Pharmacol 2001; 172:179-85. [PMID: 11312645 DOI: 10.1006/taap.2001.9158] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of the formamidine pesticides amitraz and chlordimeform on the alpha(2)-adrenergic receptor subtype that mediates the release of [(3)H]noradrenaline by synaptosomes from rat hypothalami were studied. We initially characterized the presynaptic autoreceptor on noradrenergic nerve endings using selective antagonists. Yohimbine (a nonselective alpha(2) antagonist) and BRL 44408 (selective for subtypes alpha(2A)/alpha(2D)) diminished the inhibitory effect of xylazine on K(+)-evoked release of [(3)H]noradrenaline; the K(B) values were 481 and 154 nM, respectively. In contrast, prazosin (a selective alpha(2B)/alpha(2C) antagonist) did not modify the inhibitory effect of xylazine. These results indicate that the release of noradrenaline by noradrenergic nerve endings in the rat hypothalamus is regulated by alpha(2D)-adrenoceptors, a species variation of the human alpha(2A) subtype. We then assessed the effects of the two pesticides on the K(+)-evoked release of [(3)H]noradrenaline. Amitraz reduced release in a dose-dependent manner; the effect observed at the maximal concentration tested (10 microM) was 13.0 +/- 2.0% and it was reversed by yohimbine. Amitraz also diminished the inhibitory effects of the alpha(2)-adrenergic agonists clonidine and xylazine. Chlordimeform displayed no effects, possibly because the true active compound of this insecticide is its demethylated metabolite. Based on these findings we conclude that the formamidine pesticides act as partial agonists of presynaptic alpha(2D)-adrenergic receptors in the rat hypothalamus. This interaction may be responsible for the in vivo alterations in catecholaminergic regulation of cyclic variations in gonadotropin-releasing hormone (GnRH) secretion, which can have grave functional repercussions on the reproductive system of mammals exposed to these xenobiotics.
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Affiliation(s)
- D Altobelli
- Institute of Pharmacology, Catholic University of Sacred Heart School of Medicine, Rome, Italy
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206
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Willems EW, Heiligers JP, De Vries P, Tom B, Kapoor K, Villalón CM, Saxena PR. A61603-induced vasoconstriction in porcine carotid vasculature: involvement of a non-adrenergic mechanism. Eur J Pharmacol 2001; 417:195-201. [PMID: 11334851 DOI: 10.1016/s0014-2999(01)00898-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It has recently been shown that the pharmacological profile of alpha(1)-adrenoceptors mediating constriction of porcine carotid arteriovenous anastomoses resembles that of alpha(1A)- and alpha(1B)-adrenoceptor subtypes. In an attempt to verify the involvement of alpha(1A)-adrenoceptors, we used the potent alpha(1A)-adrenoceptor agonist N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydro-naphthalen-1-yl]methane sulphonamide (A61603) and found that intracarotid (i.c.) administration of A61603 (0.3-10 microg kg(-1)) dose-dependently decreased porcine carotid blood flow and vascular conductance. This decrease was exclusively due to a constriction of carotid arteriovenous anastomoses; the capillary blood flow and conductance remained unchanged. Surprisingly, the responses to A61603 were little modified by prior i.v. treatment with 5-methylurapidil (1000 microg kg(-1)), prazosin (100 microg kg(-1)) or a combination of prazosin and rauwolscine (100 and 300 microg kg(-1), respectively). The 5-HT(1B/1D) receptor antagonist N-[4-methoxy-3-(4-methyl-1-piperazinyl) phenyl]-2'-methyl-4'(5-methyl-1,2,4-oxadiazol-3-yl)[1,1,-biphenyl]-4-carboxamide hydrochloride monohydrate (GR127935; 500 microg kg(-1)) and ketanserin (500 microg kg(-1)) also failed to modify carotid vascular responses to A61603, but, interestingly, methiothepin (3000 microg kg(-1)) proved to be an effective antagonist. Taken together, the present results show that A61603 is a relatively poor agonist at the alpha(1A)-adrenoceptor in anaesthetised pigs and that the carotid vasoconstriction produced by A61603 is mediated by a novel non-adrenergic mechanism.
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Affiliation(s)
- E W Willems
- Department of Pharmacology, Dutch Migraine Research Group and Cardiovascular Research Institute "COEUR", Faculty of Medicine and Health Science, Erasmus University Medical Centre Rotterdam "EMCR", P.O. Box 1738, 3000 DR Rotterdam, Netherlands
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207
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Ohno T, Shimizu T, Kato S, Hayashi H, Hirai S. Effect of tamsulosin hydrochloride on sympathetic hyperactivity in amyotrophic lateral sclerosis. Auton Neurosci 2001; 88:94-8. [PMID: 11474551 DOI: 10.1016/s1566-0702(01)00217-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We assessed subclinical sympathetic hyperactivity in amyotrophic lateral sclerosis (ALS) patients, which might be followed by an autonomic spell leading to circulatory collapse, or sudden death as the disease progresses, and investigated the effect of tamsulosin hydrochloride (TSHC) on sympathetic hyperactivity. We measured the plasma norepinephrine (NE) concentrations of 41 ALS patients and 10 normal controls. TSHC, a selective alpha 1 blocker. was then administered to 10 ALS patients who had high plasma NE and to the 10 normal controls. Subsequent plasma NE change was evaluated for the possible alleviating effect of TSHC on subclinical sympathetic hyperactivity in ALS. Plasma NE was high in 20 of the ALS patients (48.8%), but had no relation to respiratory problems, which supports the previous speculation that plasma NE increases in ALS are not secondary to respiratory deficit, but reflect the primary pathomechanism of the disease. ALS patients showed a marked decrease in the NE concentration after TSHC administration, whereas there was no change in the controls. In conclusion, TSHC may be useful for suppressing central sympathetic hyperactivity, presumably the primary pathomechanism in ALS, and for preventing autonomic spells during the advanced stage of the disease.
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Affiliation(s)
- T Ohno
- Department of Neurology, Tokyo Metropolitan Neurological Hospital, Fuchu, Japan
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208
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Taoda M, Adachi YU, Uchihashi Y, Watanabe K, Satoh T, Vizi ES. Effect of dexmedetomidine on the release of [3H]-noradrenaline from rat kidney cortex slices: characterization of alpha2-adrenoceptor. Neurochem Int 2001; 38:317-22. [PMID: 11137626 DOI: 10.1016/s0197-0186(00)00096-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The presynaptic modulation of [3H]-noradrenaline (NA) release from rat kidney cortex slices, a method used for the first time, was investigated. Rat kidney cortex slices were loaded with [3H]-NA and the release of radioactivity at rest and in response to field stimulation was determined. The alpha(2)-adrenoceptor agonist, dexmedetomidine inhibited the stimulation-evoked release of NA from kidney slices in a concentration-dependent manner, whereas alpha(2)-adrenoceptor antagonist CH-38083 (7,8-methyenedioxy-14-alpha-hydroxyalloberbane HCl), an alpha(2)-adrenoceptor antagonists, enhanced it. When dexmedetomidine and BRL-44408, a selective alpha(2A) antagonist, were added together, the effect of dexmedetomidine was significantly antagonized. In contrast, ARC-239 (2-(2,4-(o-piperazine-1-yl)-ethyl-4,4-dimethyl-1,3-(2H, 4H)disoguinolinedione chloride), a selective alpha(2B)-antagonist, had no effect on the release and failed to prevent the effect of dexmedetomidine. Prazosin, an alpha(1)- and alpha(2B/C)-adrenoceptor antagonist enhanced the release evoked by field stimulation. It is therefore suggested that there is a negative feedback modulation of NA release at the sympathetic innervation of kidney cortex, and dexmedetomidine, a clinically used anesthetic adjunct inhibits the release via activation of alpha(2C)-adrenoceptors.
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Affiliation(s)
- M Taoda
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, PO Box 67, H-1450, Budapest, Hungary
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209
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Hein L. Transgenic models of alpha 2-adrenergic receptor subtype function. Rev Physiol Biochem Pharmacol 2001; 142:161-85. [PMID: 11190578 DOI: 10.1007/bfb0117493] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Affiliation(s)
- L Hein
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
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210
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Willems EW, Heiligers JP, De Vries P, Kapoor K, Tom B, Villalón CM, Saxena PR. Alpha1-adrenoceptor subtypes mediating vasoconstriction in the carotid circulation of anaesthetized pigs: possible avenues for antimigraine drug development. Cephalalgia 2001; 21:110-9. [PMID: 11422093 DOI: 10.1046/j.1468-2982.2001.00167.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It has recently been shown that the alpha-adrenoceptors mediating vasoconstriction of porcine carotid arteriovenous anastomoses resemble both alpha1- and alpha2-adrenoceptors, but no attempt was made to identify the specific subtypes (alpha1A, alpha1B and alpha1D) involved. Therefore, the present study was designed to elucidate the specific subtype(s) of alpha1-adrenoceptors involved in the above response, using the alpha1-adrenoceptor agonist phenylephrine and alpha1-adrenoceptor antagonists 5-methylurapidil (alpha1A), L-765 314 (alpha1B) and BMY 7378 (alpha1D). Ten-minute intracarotid infusions of phenylephrine (1, 3 and 10 microgkg-1.min-1) induced a dose-dependent decrease in total carotid and arteriovenous anastomotic conductance, accompanied by a small tachycardia. These carotid vascular effects were abolished by L-765 314 (1000 microgkg-1; i.v.), while these responses were only attenuated by 5-methylurapidil (1000 microgkg-1; i.v.), and BMY 7378 (1000 microgkg-1; i.v.). Furthermore, intravenous bolus injections of phenylephrine (3 and 10 microgkg-1) produced a dose-dependent vasopressor response, which was only affected by 1000 microgkg-1 of 5-methylurapidil, while the other antagonists were ineffective. These results, coupled to the binding affinities of the above antagonists at the different alpha1-adrenoceptors, suggest that both alpha1A- and alpha1B-adrenoceptors mediate constriction of carotid arteriovenous anastomoses in anaesthetized pigs. In view of the less ubiquitous nature of alpha1B- compared to alpha1A-adrenoceptors, the development of potent and selective alpha1B-adrenoceptor agonists may prove to be important for the treatment of migraine.
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Affiliation(s)
- E W Willems
- Department of Pharmacology, Dutch Migraine Research Group and Cardiovascular Research Institute 'COEUR', Erasmus University Medical Centre Rotterdam, 3000 DR Rotterdam, The Netherlands
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211
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Westfall TD, Westfall DP. Pharmacological techniques for the in vitro study of the vas deferens. J Pharmacol Toxicol Methods 2001; 45:109-22. [PMID: 11687379 DOI: 10.1016/s1056-8719(01)00144-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- T D Westfall
- Department of Renal Pharmacology, GlaxoSmithKline, 709 Swedeland Road, P.O. Box 1539, King of Prussia, PA 19406-0939, USA.
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212
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Willems EW, Valdivia LF, Saxena PR, Villalón CM. The role of several alpha(1)- and alpha(2)-adrenoceptor subtypes mediating vasoconstriction in the canine external carotid circulation. Br J Pharmacol 2001; 132:1292-8. [PMID: 11250880 PMCID: PMC1572658 DOI: 10.1038/sj.bjp.0703915] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2000] [Revised: 11/20/2000] [Accepted: 12/20/2000] [Indexed: 11/08/2022] Open
Abstract
1. It has recently been shown that both alpha(1)- and alpha(2)-adrenoceptors mediate vasoconstriction in the canine external carotid circulation. The present study set out to identify the specific subtypes (alpha(1A), alpha(1B) and alpha(1D) as well as alpha(2A), alpha(2B) and alpha(2C)) mediating the above response. 2. Consecutive 1 min intracarotid infusions of phenylephrine (alpha(1)-adrenoceptor agonist) and BHT933 (alpha(2)-adrenoceptor agonist) produced dose-dependent decreases in external carotid blood flow, without affecting mean arterial blood pressure or heart rate. 3. The responses to phenylephrine were selectively antagonized by the antagonists, 5-methylurapidil (alpha(1A)) or BMY7378 (alpha(1D)), but not by L-765,314 (alpha(1B)), BRL44408 (alpha(2A)), imiloxan (alpha(2B)) or MK912 (alpha(2C)). In contrast, only BRL44408 or MK912 affected the responses to BHT933. 4. The above results support our contention that mainly the alpha(1A), alpha(1D), alpha(2A) and alpha(2C)-adrenoceptor subtypes mediate vasoconstriction in the canine external carotid circulation.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Adrenergic alpha-Antagonists/pharmacology
- Animals
- Azepines/pharmacology
- Blood Pressure/drug effects
- Carotid Artery, External/drug effects
- Carotid Artery, External/physiology
- Dogs
- Female
- Imidazoles/pharmacology
- Indoles/pharmacology
- Isoindoles
- Male
- Phenylephrine/pharmacology
- Piperazines/pharmacology
- Prazosin/analogs & derivatives
- Prazosin/pharmacology
- Quinolizines/pharmacology
- Receptors, Adrenergic, alpha-1/drug effects
- Receptors, Adrenergic, alpha-1/physiology
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/physiology
- Regional Blood Flow/drug effects
- Vasoconstriction/drug effects
- Vasoconstriction/physiology
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Affiliation(s)
- Edwin W Willems
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam ‘EMCR', P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
| | - Luis Felipe Valdivia
- Departamento de Farmacobiología, CINVESTAV-IPN, Calzada de los Tenorios 235, Col. Granjas Coapa, 14330 México D.F., México
| | - Pramod R Saxena
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam ‘EMCR', P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
| | - Carlos M Villalón
- Departamento de Farmacobiología, CINVESTAV-IPN, Calzada de los Tenorios 235, Col. Granjas Coapa, 14330 México D.F., México
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213
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Umland SP, Wan Y, Shah H, Billah M, Egan RW, Hey JA. Receptor reserve analysis of the human alpha(2C)-adrenoceptor using. Eur J Pharmacol 2001; 411:211-21. [PMID: 11164378 DOI: 10.1016/s0014-2999(00)00909-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Here we determine for norepinephrine, (5-bromo-6-(2-imidazolin-2-ylamino)quinoxaline) (UK14,304), 5,6,7,8-tetrahydro-6-(2-propenyl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (BHT-920), (2-[3-hydroxy-2,6-dimethyl-4-t-butylbenzyl]-2-imidazoline) (oxymetazoline), and ((R)-3-Hydroxy-alpha-[(methylamino)methyl]-benzenemethanol hydrochloride) (phenylephrine), affinities using a radiolabeled agonist and antagonist, and potency and efficacy values in membrane [(35)S]guanosine-5'-O-(3-thiotriphosphate) ([(35)S]GTP gamma S) binding and cAMP cellular inhibition assays, in Chinese hamster ovary cells (CHO-K1) expressing the human alpha(2c)-adrenoceptor. These cells express a high ratio of receptor to G-protein because each agonist, but not several antagonists, displaced [(3)H]UK14,304 with higher affinity than [(3)H]rauwolscine. The rank order of potency of high affinity K(i) and EC(50) in both functional assays was norepinephrine > or =UK14,304>BHT-920>oxymetazoline>phenylephrine. The receptor reserve of G-protein activation and cAMP responses was measured with the irreversible antagonist, benextramine; K(A) values of norepinephrine or UK14,304 were similar (289, 271 or 150, 163 nM, respectively). A 20-fold greater receptor occupancy was required for agonist-induced half-maximal [(35)S]GTP gamma S binding compared to cAMP inhibition, indicating significant signal amplification in cells. Therefore, the G-protein activation assay is better at distinguishing full and partial agonists.
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Affiliation(s)
- S P Umland
- Schering-Plough Research Institute, 2015 Galloping Hill Road, K15-1-1700, Kenilworth, NJ 07033, USA.
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214
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Féraille E, Doucet A. Sodium-potassium-adenosinetriphosphatase-dependent sodium transport in the kidney: hormonal control. Physiol Rev 2001; 81:345-418. [PMID: 11152761 DOI: 10.1152/physrev.2001.81.1.345] [Citation(s) in RCA: 340] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Tubular reabsorption of filtered sodium is quantitatively the main contribution of kidneys to salt and water homeostasis. The transcellular reabsorption of sodium proceeds by a two-step mechanism: Na(+)-K(+)-ATPase-energized basolateral active extrusion of sodium permits passive apical entry through various sodium transport systems. In the past 15 years, most of the renal sodium transport systems (Na(+)-K(+)-ATPase, channels, cotransporters, and exchangers) have been characterized at a molecular level. Coupled to the methods developed during the 1965-1985 decades to circumvent kidney heterogeneity and analyze sodium transport at the level of single nephron segments, cloning of the transporters allowed us to move our understanding of hormone regulation of sodium transport from a cellular to a molecular level. The main purpose of this review is to analyze how molecular events at the transporter level account for the physiological changes in tubular handling of sodium promoted by hormones. In recent years, it also became obvious that intracellular signaling pathways interacted with each other, leading to synergisms or antagonisms. A second aim of this review is therefore to analyze the integrated network of signaling pathways underlying hormone action. Given the central role of Na(+)-K(+)-ATPase in sodium reabsorption, the first part of this review focuses on its structural and functional properties, with a special mention of the specificity of Na(+)-K(+)-ATPase expressed in renal tubule. In a second part, the general mechanisms of hormone signaling are briefly introduced before a more detailed discussion of the nephron segment-specific expression of hormone receptors and signaling pathways. The three following parts integrate the molecular and physiological aspects of the hormonal regulation of sodium transport processes in three nephron segments: the proximal tubule, the thick ascending limb of Henle's loop, and the collecting duct.
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Affiliation(s)
- E Féraille
- Division of Nephrology, Geneva University Hospital, Geneva, Switzerland.
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215
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Abstract
The control and maintenance of vascular tone is due to a balance between vasoconstrictor and vasodilator pathways. Vasomotor responses to neural, metabolic and physical factors vary between vessels in different vascular beds, as well as along the same bed, particularly as vessels become smaller. These differences result from variation in the composition of neurotransmitters released by perivascular nerves, variation in the array and activation of receptor subtypes expressed in different vascular beds and variation in the signal transduction pathways activated in either the vascular smooth muscle or endothelial cells. As the study of vasomotor responses often requires pre-existing tone, some of the reported heterogeneity in the relative contributions of different vasodilator mechanisms may be compounded by different experimental conditions. Biochemical variations, such as the expression of ion channels, connexin subtypes and other important components of second messenger cascades, have been documented in the smooth muscle and endothelial cells in different parts of the body. Anatomical variations, in the presence and prevalence of gap junctions between smooth muscle cells, between endothelial cells and at myoendothelial gap junctions, between the two cell layers, have also been described. These factors will contribute further to the heterogeneity in local and conducted responses.
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Affiliation(s)
- C E Hill
- Autonomic Synapse Group, Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra 0200 ACT, Australia.
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216
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Rudling JE, Richardson J, Evans PD. A comparison of agonist-specific coupling of cloned human alpha(2)-adrenoceptor subtypes. Br J Pharmacol 2000; 131:933-41. [PMID: 11053214 PMCID: PMC1572406 DOI: 10.1038/sj.bjp.0703644] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The agonist-specific coupling properties of the three cloned human alpha(2)-adrenoceptor subtypes have been compared, when expressed at similar levels in Chinese hamster ovary (CHO) cell lines, using noradrenaline and (+/-)-meta-octopamine as agonists. Noradrenaline can couple the receptor to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production in all three receptor subtypes, with the relative strength of the coupling to the pathways varying for each of the receptor subtypes. meta-Octopamine selectively couples the alpha(2A)-adrenoceptor only to the inhibition of forskolin-stimulated cyclic AMP production. However, meta-octopamine couples the alpha(2B)- and alpha(2C)-adrenoceptors to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production. The relative potency of meta-octopamine to noradrenaline varies between the different alpha(2)-adrenoceptor subtypes. The effects of meta-octopamine are around two orders of magnitude less potent than those of noradrenaline on both the alpha(2A)- and alpha(2B)-adrenoceptor subtypes. In contrast, in the case of the alpha(2C)-adrenoceptor, meta-octopamine is only one order of magnitude less potent than noradrenaline in the stimulation of forskolin-stimulated cyclic AMP production and, in addition, is equipotent with noradrenaline in the inhibition of forskolin-stimulated cyclic AMP production and has an increased maximal response. This raises the possibility that meta-octopamine may have physiologically important actions via alpha(2C)-adrenoceptors in vivo. The results show that the modulation of cyclic AMP production occurs in both a subtype- and agonist-specific manner for alpha(2A)-adrenoceptors and in a subtype specific manner for alpha(2B)- and alpha(2C)-adrenoceptors.
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Affiliation(s)
- Jane E Rudling
- The Babraham Institute Laboratory of Receptor Signalling, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ
| | - Jo Richardson
- The Babraham Institute Laboratory of Receptor Signalling, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ
| | - Peter D Evans
- The Babraham Institute Laboratory of Receptor Signalling, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ
- Author for correspondence:
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217
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Dardonville C, Goya P, Rozas I, Alsasua A, Martín MI, Borrego MJ. New aromatic iminoimidazolidine derivatives as alpha1-adrenoceptor antagonists: a novel synthetic approach and pharmacological activity. Bioorg Med Chem 2000; 8:1567-77. [PMID: 10976505 DOI: 10.1016/s0968-0896(00)00089-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The design, synthesis and alpha1-adrenoceptor antagonism of a series of bis-imidazoline (1a, 2a, 3a and 4a) and bis-guanidine (1b, 2b, 3b and 4b) diphenyl derivatives are reported. All of these compounds fulfill the conditions of the most recent pharmacophore proposed for alpha1-adrenoceptors and found in the literature. Besides, a novel synthetic approach to the preparation of 2-(arylimino)imidazolidine derivatives is described. All the tested compounds, except the bis-guanidinium derivative 3b, inhibit the contractile responses induced by noradrenaline in aortic rings of rat and rabbit in a dose-dependent manner. Our results indicate that, even though some discrepancies are observed in terms of the alpha1 subtype targeted by this new family of compounds, they show an interesting profile as antagonists of alpha1-adrenoceptors and a new prototype, compound 1a, has been found deserving further development.
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MESH Headings
- Adrenergic alpha-Antagonists/chemical synthesis
- Adrenergic alpha-Antagonists/chemistry
- Adrenergic alpha-Antagonists/pharmacology
- Animals
- Aorta, Thoracic/chemistry
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/physiology
- Bradykinin/pharmacology
- Dose-Response Relationship, Drug
- Female
- Guanidine/analogs & derivatives
- Guanidine/chemistry
- Guanidine/pharmacology
- Guinea Pigs
- Imidazoles/chemical synthesis
- Imidazoles/chemistry
- Imidazoles/pharmacology
- Imines/chemical synthesis
- Imines/chemistry
- Imines/pharmacology
- Inhibitory Concentration 50
- Male
- Models, Molecular
- Muscle Contraction/drug effects
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/drug effects
- Muscle, Smooth, Vascular/physiology
- Norepinephrine/antagonists & inhibitors
- Norepinephrine/pharmacology
- Rabbits
- Rats
- Receptors, Adrenergic, alpha/metabolism
- Structure-Activity Relationship
- Vasoconstriction/drug effects
- Vasoconstrictor Agents/antagonists & inhibitors
- Vasoconstrictor Agents/pharmacology
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218
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Gudme CN, Nielsen MS, Nielsen R. Effect of alpha1-adrenergic stimulation of Cl- secretion and signal transduction in exocrine glands (Rana esculenta). ACTA PHYSIOLOGICA SCANDINAVICA 2000; 169:173-82. [PMID: 10848648 DOI: 10.1046/j.1365-201x.2000.00727.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the present work, the effect of stimulation of alpha-adrenergic receptors on Cl- secretion via exocrine frog skin glands was investigated. The alpha-adrenergic stimulation was performed by addition of the adrenergic agonist noradrenaline in the presence of the beta-adrenergic antagonist propranolol. In the presence of propranolol, noradrenaline had no effect on the cellular cAMP content. The Cl- secretion was measured as the amiloride-insensitive short circuit current (ISC). Addition of noradrenaline induced a biphasic increase in the ISC. The increase in ISC coincided with an increase in the net 36Cl- secretion. The noradrenaline-induced increase in ISC was dose-dependent with an EC50 of 13 +/- 0.3 microM. Epifluorescence microscopic measurements of isolated, fura-2-loaded frog skin gland acini were used to characterize the intracellular calcium ([Ca2+]i) response. Application of noradrenaline induced a biphasic [Ca2+]i response, which was dose-dependent with an EC50 of 11 +/- 6 microM. The Ca2+ plateau unlike the peak-response was sensitive to removal of Ca2+ from the extracellular medium. The noradrenaline-induced increase in the Cl- secretion as well as in [Ca2+]i was sensitive to the alpha1-adrenergic antagonist prazosine. Ryanodine and caffeine had no effect on [Ca2+]i indicating that the release was independent of ryanodine-sensitive Ca2+ stores. Noradrenaline mediated a significant increase in the cellular inositol 1,4,5-trisphosphate (IP3) content suggesting that the signal transduction pathway leading to the noradrenaline-induced increase in Ca2+ involved IP3 and a release of Ca2+ from IP3-sensitive stores.
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Affiliation(s)
- C N Gudme
- Department of Biochemistry, August Krogh Institute, University of Copenhagen, Denmark
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219
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Angelini G, Ketzler JT, Coursin DB. The effects of alpha2-adrenoceptor agonists on circulation and respiration. Best Pract Res Clin Anaesthesiol 2000. [DOI: 10.1053/bean.2000.0096] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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220
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Scheinin M, Pihlavisto M. Molecular pharmacology of alpha2-adrenoceptor agonists. Best Pract Res Clin Anaesthesiol 2000. [DOI: 10.1053/bean.2000.0080] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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221
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Pigini M, Quaglia W, Gentili F, Marucci G, Cantalamessa F, Franchini S, Sorbi C, Brasili L. Structure-activity relationship at alpha-adrenergic receptors within a series of imidazoline analogues of cirazoline. Bioorg Med Chem 2000; 8:883-8. [PMID: 10882000 DOI: 10.1016/s0968-0896(00)00030-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Several analogues of cirazoline (2), a selective alpha1-adrenoreceptor agonist, were prepared and their pharmacological profiles studied. Although at the alpha1-adrenoreceptor all the compounds displayed a significant agonist activity, at the alpha2-adrenoreceptor they showed either agonist or antagonist activity depending on the nature of the phenyl substituent. The qualitative structure-activity relationship led us to the conclusion that the oxygen atom in the side-chain is essential for alpha1-agonist activity, while the cyclopropyl ring is not, and may be replaced by several groups. Of the groups studied, isopropoxy appears to be the best. Instead, the same substitution (i.e., isopropoxy for the cyclopropyl ring) at alpha2-adrenoreceptors causes a reversal of activity. On the other hand, the cyclopropyl ring seems to be important for alpha1-selectivity. Compound 20 is the most potent alpha1-agonist of the series, being equiactive with cirazoline on rat vas deferens and in pithed rat.
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Affiliation(s)
- M Pigini
- Dipartimento di Scienze Chimiche, Università degli Studi di Camerino, Italy
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222
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Ross TM, Jetter MC, McDonnell ME, Boyd RE, Connelly CD, Martinez RP, Lewis MA, Codd EE, Raffa RB, Reitz AB. Alpha(2) adrenoceptor agonists as potential analgesic agents. 2. Discovery of 4-(4-imidazo)-1,3-dimethyl-6,7-dihydro-thianaphthene as a high-affinity ligand for the alpha(2D) adrenergic receptor. J Med Chem 2000; 43:1423-6. [PMID: 10753480 DOI: 10.1021/jm000128r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T M Ross
- Drug Discovery Division, The R. W. Johnson Pharmaceutical Research Institute, Spring House, Pennsylvania 19477, USA
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223
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Ross TM, Jetter MC, McDonnell ME, Boyd RE, Connelly CD, Martinez RP, Lewis MA, Codd EE, Raffa RB, Reitz AB. alpha(2) Adrenoceptor agonists as potential analgesic agents. 2. Discovery of 4-(4-Imidazo)-1,3-dimethyl-6,7-dihydrothianaphthene [corrected] as a high-affinity ligand for the alpha(2D) adrenergic receptor. J Med Chem 2000; 43:765-8. [PMID: 10715142 DOI: 10.1021/jm990569e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- T M Ross
- Drug Discovery Division, The R. W. Johnson Pharmaceutical Research Institute, Spring House, Pennsylvania 19477, USA
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224
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Varma DR, Deng XF. Cardiovascular α1-adrenoceptor subtypes: functions and signaling. Can J Physiol Pharmacol 2000. [DOI: 10.1139/y99-142] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
α1-Adrenoceptors (α1AR) are G protein-coupled receptors and include α1A, α1B, and α1D subtypes corresponding to cloned α1a, α1b, and α1d, respectively. α1AR mediate several cardiovascular actions of sympathomimetic amines such as vasoconstriction and cardiac inotropy, hypertrophy, metabolism, and remodeling. α1AR subtypes are products of separate genes and differ in structure, G protein-coupling, tissue distribution, signaling, regulation, and functions. Both α1AAR and α1BAR mediate positive inotropic responses. On the other hand, cardiac hypertrophy is primarily mediated by α1AAR. The only demonstrated major function of α1DAR is vasoconstriction. α1AR are coupled to phospholipase C, phospholipase D, and phospholipase A2; they increase intracellular Ca2+ and myofibrillar sensitivity to Ca2+ and cause translocation of specific phosphokinase C isoforms to the particulate fraction. Cardiac hypertrophic responses to α1AR agonists might involve activation of phosphokinase C and mitogen-activated protein kinase via Gq. α1AR subtypes might interact with each other and with other receptors and signaling mechanisms.Key words: cardiac hypertrophy, inotropic responses, central α1-adrenoreceptors, arrythmias.
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225
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Melchiorre C, Angeli P, Bolognesi ML, Chiarini A, Giardinà D, Gulini U, Leonardi A, Marucci G, Minarini A, Pigini M, Quaglia W, Rosini M, Tumiatti V. Alpha 1-adrenoreceptor antagonists bearing a quinazoline or a benzodioxane moiety. PHARMACEUTICA ACTA HELVETIAE 2000; 74:181-90. [PMID: 10812956 DOI: 10.1016/s0031-6865(99)00049-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- C Melchiorre
- Department of Pharmaceutical Sciences, University of Bologna, Italy
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226
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Dossin O, Moulédous L, Baudry X, Tafani JA, Mazarguil H, Zajac JM. Characterization of a new radioiodinated probe for the alpha2C adrenoceptor in the mouse brain. Neurochem Int 2000; 36:7-18. [PMID: 10566954 DOI: 10.1016/s0197-0186(99)00102-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
[125I]17alpha-hydroxy-20alpha-yohimban-16beta-(N-4-p6 hydroxyphenethyl)carboxamide or [125I]rauwolscine-OHPC, a new radioiodinated probe derived from rauwolscine was synthesized and its binding characteristics investigated on sections of the mouse caudate putamen. [125I]rauwolscine-OHPC binding was saturable and revealed interaction with a single class of binding sites (KD= 0.171 nM, Bmax = 3082 pCi/mg of tissue). The kinetically derived affinity was in close agreement with the affinity evaluated by saturation experiments: k(-1)/k(+1)(0.0403 min(-1)/114 10(6) M(-1) min(-1))=0.35 nM. Competition studies revealed interaction with one single class of binding sites for each of the twelve compounds tested. The rank of potency suggested an interaction with alpha2 adrenoceptors (atipamezole > or = RX 821002 > yohimbine > (-)epinephrine). Moreover, the good affinity of [125I] rauwolscine-OHPC binding sites for spiroxatrine, yohimbine, WB 4101, the relatively good affinity for prazosin (Ki =37.4 nM) and the affinity ratio prazosin/oxymetazoline (37.4/43.4=0.86) were consistent with an alpha2C selective labelling of [125I]rauwolscine-OHPC. The distribution of [125I]rauwolscine-OHPC binding sites in mouse brain was characterized by autoradiography. The density of binding sites was high in the islands of Calleja, accumbens nucleus, caudate putamen and olfactory tubercles, moderate in the hippocampus, amygdala and anterodorsal nucleus of the thalamus. These findings demonstrated that [125I]rauwolscine-OHPC is a useful radioiodinated probe to label alpha2C adrenoceptors in mouse brain.
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Affiliation(s)
- O Dossin
- Institut de Pharmacologie et de Biologie Structurale, CNRS UPR 9062, Toulouse, France
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227
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Hudson AL, Robinson ES, Lalies MD, Tyacke RJ, Jackson HC, Nutt DJ. In vitro and in vivo approaches to the characterization of the alpha2-adrenoceptor. JOURNAL OF AUTONOMIC PHARMACOLOGY 1999; 19:311-20. [PMID: 10961736 DOI: 10.1111/j.1365-2680.1999.tb00003.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. In order to more fully understand the role of the alpha2-adrenoceptor in brain function, a combination of in vitro and in vivo techniques were utilized including radioligand binding, autoradiography, brain microdialysis and antisense oligonucleotides. 2. Binding studies showed the tritiated form of the selective alpha2-adrenoceptor antagonist, RX821002 (methoxy-idazoxan) labelled an apparent single population of sites in rat brain membranes with high affinity (1 nM), for which prazosin had low affinity (1107 nM). Similar studies in rabbit brain membranes found that prazosin and oxymetazoline were able to displace [3H]-RX821002 in a biphasic manner indicating the presence of subtypes of alpha2-adrenoceptors. 3. Receptor autoradiography revealed a distribution of [3H]-RX821002 binding in rat brain consistent with the labelling of all alpha2-adrenoceptor subtypes, namely alpha(2A/D-), alpha2B and alpha2C. 4. In rat, in vivo brain dialysis experiments demonstrated peripherally administered RX821002 elevated basal noradrenaline in frontal cortex and also, although to a lesser extent, in ventral hippocampus. RX821002 was also able to elevate extracellular dopamine in the striatum. 5. A 7-day i.c.v. infusion of an antisense oligonucleotide targeting the alpha(2A/D)-adrenoceptor, resulted in a significant reduction in the autoradiographic density of [3H]-RX821002 binding in specific brain areas, notably the lateral septal nuclei and anterior hypothalamic area. 6. Several years of research by our group has extended our knowledge of the pharmacology and function of the alpha2-adrenoceptor and has provided evidence of the roles of this receptor in the control of monoamine turnover. The successful use of antisense technology to knockdown expression of the alpha(2A/D) subtype provides future opportunities to explore the physiology of this receptor subtype.
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Affiliation(s)
- A L Hudson
- Psychopharmacology Unit, School of Medical Sciences, University of Bristol, UK
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228
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Fabbri E, Barbin L, Capuzzo A. Non-selectivity of yohimbine for adrenergic receptors in fish liver. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART C, PHARMACOLOGY, TOXICOLOGY & ENDOCRINOLOGY 1999; 124:281-6. [PMID: 10661720 DOI: 10.1016/s0742-8413(99)00075-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Most studies on adrenergic receptors (AR) have been performed on mammalian tissues, but the adrenergic ligands routinely utilized seem not always suitable for specific interaction with fish tissues. Here we report that in isolated catfish hepatocytes, yohimbine, usually thought to act as a specific antagonist for AR of the alpha2 subtype, at high concentrations, increases adenylyl cyclase activity and synergistically enhances the forskolin-induced enzyme stimulation. Such effects are counteracted by the beta-AR antagonist propranolol, but not by the alpha-AR antagonist phentolamine. Moreover, yohimbine seems to antagonize both alpha1- and alpha2-adrenergic ligand-binding in catfish liver membrane in a manner somewhat different from the mammalian systems. Together with previous evidence that yohimbine blocks the rise of intracellular calcium induced by epinephrine via alpha1-AR, the present results seem to indicate that this compound is not a suitable tool for studying alpha2-AR in fish liver.
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Affiliation(s)
- E Fabbri
- Department of Biology, University of Bologna, Italy
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229
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Honner V, Docherty JR. Investigation of the subtypes of alpha1-adrenoceptor mediating contractions of rat vas deferens. Br J Pharmacol 1999; 128:1323-31. [PMID: 10578148 PMCID: PMC1571755 DOI: 10.1038/sj.bjp.0702913] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1 The subtypes of alpha1-adrenoceptor mediating contractions of rat vas deferens to endogenous and exogenous noradrenaline and to the exogenous agonists methoxamine, phenylephrine and A61603 have been examined. 2 The effects of antagonists on the shape of concentration-response curves, both tonic and phasic, to the four agonists were analysed. Prazosin produced parallel shifts in all cases. Particularly for RS 17053 against noradrenaline, there was some evidence for a resistant component of the agonist response. High concentrations of RS 17053 (1-10 microM) virtually abolished tonic contractions but phasic contractions were resistant. 3 A series of nine antagonists (the above and WB4101, benoxathian, phentolamine, BMY 7378, HV 723, spiperone) were investigated against contractions to noradrenaline. The correlation with the potency of the series of alpha1-adrenoceptor antagonists against contractions to noradrenaline was significant only for the alpha1A-adrenoceptor ligand binding site (r=0.88, n=9, P<0.01). 4 In epididymal portions (nifedipine 10 microM), the isometric contraction to a single electrical pulse is alpha1-adrenoceptor mediated. The correlation with ligand binding sites for 11 antagonists (the above plus ARC 239 and (+)-niguldipine) was significant only for the alpha1D-adrenoceptor subtype (r=0.65, n=11, P<0.05). 5 In conclusion, tonic contractions of rat vas deferens produced by exogenous agonists are mediated predominantly by alpha1A-adrenoceptors, although a second subtype of receptor may additionally be involved in phasic contractions. Nerve-stimulation evoked alpha1-adrenoceptor mediated contractions seem to predominantly involve non-alpha1A-adrenoceptors, and the receptor involved resembles the alpha1D-receptor.
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Affiliation(s)
- V Honner
- Department of Physiology, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
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230
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Lavelle A, Honner V, Docherty JR. Investigation of the prejunctional alpha2-adrenoceptor mediated actions of MDMA in rat atrium and vas deferens. Br J Pharmacol 1999; 128:975-80. [PMID: 10556934 PMCID: PMC1571719 DOI: 10.1038/sj.bjp.0702875] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/1999] [Revised: 08/06/1999] [Accepted: 08/11/1999] [Indexed: 11/08/2022] Open
Abstract
1. We have investigated the effects of methylenedioxymethamphetamine (MDMA, 'ecstasy') on peripheral noradrenergic neurotransmission in the rat. 2. In rat atrial slices pre-incubated with [3H]-noradrenaline and in the presence of desipramine (1 micronM) to prevent effects of MDMA on basal outflow of tritium, MDMA (10 micronM) significantly inhibited the release of tritium evoked by short trains of six pulses at 100 Hz every 10 s for 3 min. This effect did not occur in the presence of the alpha2-adrenoceptor antagonist yohimbine (1 micronM). 3. In epididymal portions of rat vas deferens in the presence of nifedipine (10 micronM), MDMA produced a concentration-dependent inhibition of single pulse nerve stimulation-evoked contractions with a pD2 of 5.88+/-0.16 (n=4). Inhibitory effects of MDMA were antagonized by the alpha2-adrenoceptor antagonist yohimbine (0.3 micronM), but not by the 5-hydroxytryptamine receptor antagonist cyanopindolol in a concentration (1 micronM) which markedly antagonized the inhibitory actions of the 5-HT-1 receptor agonist 5-carboxamidotryptamine. 4. In prostatic portions of rat vas deferens in the presence of cocaine (3 micronM), MDMA produced a concentration-dependent inhibition of single pulse nerve stimulation-evoked contractions with a pD2 of 5. 12+/-0.21 (n=4). In the absence of cocaine, only the highest concentration of MDMA (30 micronM) produced an inhibition, but the alpha2-adrenoceptor antagonist yohimbine (0.3 micronM) converted the response to MDMA from inhibition to potentiation of the stimulation-evoked contraction. 5. In radioligand binding studies, MDMA showed similar affinities for alpha2B, alpha2C and alpha2D-adrenoceptor sites, with pKi values of 5.14+/-0.16, 5.11+/-0. 05 and 5.31+/-0.14, respectively. 6 It is concluded that MDMA has significant alpha2-adrenoceptor agonist actions.
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Affiliation(s)
- Aisling Lavelle
- Department of Physiology, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
| | - Valerie Honner
- Department of Physiology, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
| | - J R Docherty
- Department of Physiology, Royal College of Surgeons in Ireland, 123 St. Stephen's Green, Dublin 2, Ireland
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231
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Silva MA, Megale A, Avellar MC, Porto CS. Expression and pharmacological characterization of alpha1-adrenoceptors in rat seminal vesicle. Eur J Pharmacol 1999; 381:141-9. [PMID: 10554882 DOI: 10.1016/s0014-2999(99)00563-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the present study, we investigated the alpha1-adrenoceptor subtypes mediating adrenaline-induced contractions of the rat seminal vesicle by using functional studies. The reverse transcription combined with polymerase chain reaction (RT-PCR) was also used to identify of alpha1-adrenoceptor mRNA subtypes. The rank order of potency of alpha1-adrenoceptor antagonists in blocking the contractile effects of adrenaline was: prazosin = WB 4101 >>> BMY 7378 > chloroethylclonidine, indicating the presence of alpha1A-adrenoceptors in the rat seminal vesicle. In the presence of nifedipine, there was a 76% reduction in the adrenaline-induced contractions. The nifedipine-insensitive component (24%) of the contractile response to adrenaline was unaffected by chloroethylclonidine. A small pool of spare alpha1-adrenoceptors for adrenaline (0.10%) was also detected. All three alpha1-adrenoceptor subtypes were amplified when RT-PCR was performed on total RNA isolated from rat seminal vesicle. In conclusion, these data indicate the presence of three alpha1-adrenoceptor mRNA subtypes, but only alpha1A-adrenoceptors are involved in the rat seminal vesicle contraction.
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Affiliation(s)
- M A Silva
- Department of Pharmacology, Universidade Federal de São Paulo-Escola Paulista de Medicina, SP, Brazil
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232
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Pupo AS, Cavenaghi DL, Campos M, Lucena Morais P, Jurkiewicz NH, Jurkiewicz A. Effects of indoramin in rat vas deferens and aorta: concomitant alpha1-adrenoceptor and neuronal uptake blockade. Br J Pharmacol 1999; 127:1832-6. [PMID: 10482913 PMCID: PMC1566180 DOI: 10.1038/sj.bjp.0702735] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The actions of the alpha1-adrenoceptor antagonist indoramin have been examined against the contractions induced by noradrenaline in the rat vas deferens and aorta taking into account a putative neuronal uptake blocking activity of this antagonist which could result in self-cancelling actions. 2. Indoramin behaved as a simple competitive antagonist of the contractions induced by noradrenaline in the vas deferens and aorta yielding pA2 values of 7.38+/-0.05 (slope=0.98+/-0.03) and 6.78+/-0.14 (slope=1.08+/-0.06), respectively. 3. When the experiments were repeated in the presence of cocaine (6 microM) the potency (pA2) of indoramin in antagonizing the contractions of the vas deferens to noradrenaline was increased to 8.72+/-0.07 (slope=1.10+/-0.05) while its potency remained unchanged in the aorta (pA2=6.69+/-0.12; slope=1.04+/-0.05). 4. In denervated vas deferens, indoramin antagonized the contractions to noradrenaline with a potency similar to that found in the presence of cocaine (8.79+/-0.07; slope=1.09+/-0.06). 5. It is suggested that indoramin blocks alpha1-adrenoceptors and neuronal uptake in rat vas deferens resulting in Schild plots with slopes not different from unity even in the absence of selective inhibition of neuronal uptake. As a major consequence of this double mechanism of action, the pA2 values for this antagonist are underestimated when calculated in situations where the neuronal uptake is active, yielding spurious pKB values.
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Affiliation(s)
- A S Pupo
- Department of Pharmacology, Instituto de Biociências, UNESP, CEP 18600-000, Botucatu, Brazil
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