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Hypertension: history and development of established and novel treatments. Clin Res Cardiol 2018; 107:16-29. [DOI: 10.1007/s00392-018-1299-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 06/11/2018] [Indexed: 01/08/2023]
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Affiliation(s)
- B N C Prichard
- Medical Unit, Uniiversity College Hospital Medlical School, London
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Skrzypecki J, Ufnal M. Drug resistant hypertension – no simple way out. Kidney Blood Press Res 2016; 40:66-76. [PMID: 25791632 DOI: 10.1159/000368483] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/20/2015] [Indexed: 11/19/2022] Open
Abstract
Hypertension poses growing challenge for health policy-makers and doctors worldwide. Recently published results of Symplicity-III trial (HTN-3), the first blinded, randomized, multicenter study on the efficacy of renal denervation for the treatment of resistant hypertension did not show a significant reduction of BP in patients with resistant hypertension 6 months after renal-artery denervation, as compared with controls. In this paper we review clinical and experimental studies on renal denervation. In order to identify causes of inconsistent results in renal denervation studies we look at basic science support for renal denervation and at designs of clinical trials.
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Prichard BN, Johnston AW, Hill ID, Rosenheim ML. Bethanidine, Guanethidine, and Methyldopa in Treatment of Hypertension: a Within-patient Comparison. BRITISH MEDICAL JOURNAL 2011; 1:135-44. [PMID: 20791420 DOI: 10.1136/bmj.1.5585.135] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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van Zwieten PA. The central action of antihypertensive drugs, mediated via central α -receptors. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1973.tb09127.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- P A van Zwieten
- Department of Biopharmacy, University of Amsterdam, Roetersstraat 1, The Netherlands
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Affiliation(s)
- David Story
- Faculty of Life Sciences, RMIT University, Melbourne, Victoria, Australia
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Abstract
Abstract
L-α-Methyldopa, which normally causes sedation, induces a strong central excitation in mice pretreated with a monoamine oxidase inhibitor after a lag of a few hours. It is concluded that this excitation is caused by accumulation of free catecholamines liberated by amines which are slowly formed by decarboxylation of α-methyldopa. The hypotensive and sedative effects of α-methyldopa given alone are attributed to the slow release of catecholamines and subsequent breakdown by monoamine oxidase so that a partial depletion of catecholamines ensues.
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DAY MD, RAND MJ. SOME OBSERVATIONS ON THE PHARMACOLOGY OF ALPHA-METHYLDOPA. BRITISH JOURNAL OF PHARMACOLOGY AND CHEMOTHERAPY 1996; 22:72-86. [PMID: 14126060 PMCID: PMC1703913 DOI: 10.1111/j.1476-5381.1964.tb01545.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
alpha-Methyldopa in high concentrations impaired the responses of rabbit isolated ileum and guinea-pig isolated vas deferens to stimulation of the sympathetic nerves and to noradrenaline, but these preparations taken from animals previously treated with alpha-methyldopa showed no sign of impairment. Contractions of the cat nictitating membrane were reduced but not abolished by alpha-methyldopa. In cats, dogs and rats, pressor responses to noradrenaline were usually slightly increased by alpha-methyldopa. Pressor responses to tyramine were not affected consistently. alpha-Methyldopa, alpha-methyldopamine and alpha-methylnoradrenaline behaved like dopa, dopamine and noradrenaline respectively in restoring the responses of tissues from reserpine-treated animals to stimulation of the sympathetic nerves to the rabbit ileum, the guinea-pig vas deferens and the cat nictitating membrane and in restoring responses to tyramine of the cat blood pressure and nictitating membrane, and the rat blood pressure. The potency of alpha-methylnoradrenaline relative to noradrenaline ranged from one-half to one-ninth on various preparations. The results are discussed in relation to the antihypertensive action of alpha-methyldopa.
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KOPIN IJ, FISCHER JE, MUSACCHIO J, HORST WD. EVIDENCE FOR A FALSE NEUROCHEMICAL TRANSMITTER AS A MECHANISM FOR THE HYPOTENSIVE EFFECT OF MONOAMINE OXIDASE INHIBITORS. Proc Natl Acad Sci U S A 1996; 52:716-21. [PMID: 14212547 PMCID: PMC300335 DOI: 10.1073/pnas.52.3.716] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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CHAMBERLAIN DA, HOWARD J. GUANETHIDINE AND METHYLDOPA: A HAEMODYNAMIC STUDY. BRITISH HEART JOURNAL 1996; 26:528-36. [PMID: 14196136 PMCID: PMC1018172 DOI: 10.1136/hrt.26.4.528] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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QUINTON RM, HALLIWELL G. EFFECTS OF ALPHA-METHYL DOPA AND DOPA ON THE AMPHETAMINE EXCITATORY RESPONSE IN RESERPINIZED RATS. Nature 1996; 200:178-9. [PMID: 14073041 DOI: 10.1038/200178a0] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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HURKMANS AT. MECHANISM OF ACTION OF PSYCHOMOTOR STIMULANT DRUGS. SIGNIFICANCE OF DOPAMINE IN LOCOMOTOR STIMULANT ACTION. ACTA ACUST UNITED AC 1996; 3:227-39. [PMID: 14336531 DOI: 10.1016/0028-3908(64)90012-7] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Kopin IJ. In-vivo quantitative imaging of catecholaminergic nerve terminals in brain and peripheral organs using positron emission tomography (PET). JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1990; 32:19-27. [PMID: 2089090 DOI: 10.1007/978-3-7091-9113-2_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Positron emission tomography (PET), has made possible quantitative imaging of the origins of positron-emitting isotopes, such as 11C and 18F, in intact animals and in humans. Lack of absolute specificity of enzymes, storage mechanisms and transporters allows 11C-or 18F-labelled "false transmitters" to be formed, stored and released from nerve terminals. Discussed are the assumptions, limitations, and advantages of 18F-6-fluoroDOPA, 18F-6-fluorodopamine, 18F-6-fluorometaraminol, and 11C-N-methyl-metaraminol (m-hydroxyephedrine) for PET imaging of dopaminergic nerve terminals in brain or sympathetic innervation in peripheral organs.
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Tung CS, Goldberg MR, Hollister AS, Sweetman BJ, Robertson D. Depletion of brainstem epinephrine stores by alpha-methyldopa: possible relation to attenuated sympathetic outflow. Life Sci 1988; 42:2365-71. [PMID: 3287081 DOI: 10.1016/0024-3205(88)90190-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The antihypertensive effect of alpha-methyldopa (MD) is believed to be critically dependent on its ability to deplete endogenous catecholamines or cause the synthesis of false neurotransmitters. We used liquid chromatography with electrochemical detection (LCEC) and negative chemical ionization gas chromatography-mass spectrometry (GC-MS) for quantitation of catecholamines and MD metabolites in rat. MD intraperitoneally (100 mg/kg q12 hr X 12 days), significantly increased alpha-methylnorepinephrine (MNE) in brain (1.02 +/- 0.33 micrograms/g), heart (1.67 +/- 0.57 micrograms/g) and adrenal glands (114.93 +/- 50.47 micrograms/g) Endogenous norepinephrine (NE), epinephrine (E) and dopamine (DA) were reduced. ME levels were 2.19 +/- 0.44 micrograms/g (n = 6) in the adrenal gland but only 99 +/- 26 pg/g (n = 3) in the brainstem. MD-induced endogenous brainstem NE depletion was more than compensated by MNE production, but brainstem E depletion was not compensated for by a stoichiometric production of brainstem ME. We conclude (1) although ME is a metabolite of MD, it is present in extremely low concentrations in brainstem and (2) central epinephrine-containing neurons are depleted of neurotransmitter by MD therapy. If this selective epinephrine depletion occurs in the bulbospinal tract neurons responsible for maintaining sympathetic tone, then this effect could contribute to the antihypertensive effect of MD.
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Affiliation(s)
- C S Tung
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan, Republic of China
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Christensen HD, Koss MC, Gherezghiher T. Synaptic organization in the oculomotor nucleus. Ann N Y Acad Sci 1986; 473:382-99. [PMID: 3541736 DOI: 10.1111/j.1749-6632.1986.tb23630.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Langham ME. The intraocular pressure and the pupillary responses of conscious rabbits to racemic erythro-alpha-methylnorepinephrine. Exp Eye Res 1984; 39:781-90. [PMID: 6151514 DOI: 10.1016/0014-4835(84)90077-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The intraocular pressure and the pupillary responses in conscious rabbits to racemic erythro-alpha-methylnorepinephrine (alpha MeNE) have been investigated and its activity compared to L-norepinephrine (NE). Aqueous solutions of alpha MeNE applied topically caused dose-dependent decreases of intraocular pressure and of pupil dilatation. The maximal intraocular pressure response to alpha MeNE exceeded that to NE, and the sensitivity of the intraocular pressure response exceeded that to NE by 10-20 times. The onset of the decrease in intraocular pressure to alpha MeNE was rapid and contrasted to the slow onset of the intraocular hypotensive response to NE. Preganglionic cervical sympathotomy did not effect the intraocular pressure and the pupillary responses to either alpha MeNE or NE. Superior cervical ganglionectomy induced supersensitivity to NE but not to alpha MeNE. Studies using alpha 1, alpha 2, and beta adrenoceptor antagonists indicated that the intraocular pressure responses to alpha MeNE were mediated primarily by alpha 2 and beta adrenoceptors whereas the responses to NE were mediated primarily by alpha 1 adrenoceptors. The observations are discussed in the light of recent data of the affinities of alpha MeNE and NE to alpha 1, alpha 2, and beta adrenoceptors. The high potency of alpha MeNE compared to NE in decreasing intraocular pressure and in dilating the pupil does not correlate with their binding affinities to alpha and beta adrenoceptors. The observations support an alternative explanation that the differences in the potencies of alpha MeNE and NE are due to differences in rates of inactivation of the two compounds in the adrenergic neurone.
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Abstract
Agents that work primarily by inhibiting effects of the sympathetic nervous system continue to be widely used for the therapy of hypertension. There are two principal types of drugs: those that work in the central nervous system, and those that act primarily at peripheral neuromuscular sites. Both types of drugs are often effective as single-agent therapy although they also work well in combination with diuretics and other antihypertensive agents. Recently, there has been interest in a new transdermal method for administering the centrally-acting drug clonidine; the consistency of the plasma drug concentrations achieved by this form of treatment appears to minimize adverse effects while providing continuous therapeutic efficacy. Interest is also focusing on the ability of sympathoinhibitory agents such as alpha-methyldopa to produce regression of left ventricular hypertrophy, possibly by mechanisms independent of their antihypertensive action.
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Melman A, Fersel J, Weinstein P. Further Studies on the Effect of Chronic Alpha-Methyldopa Administration Upon the Central Nervous System and Sexual Function in Male Rats. J Urol 1984; 132:804-8. [PMID: 6540816 DOI: 10.1016/s0022-5347(17)49878-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Previous studies in our laboratory have demonstrated that alpha-methyldopa, a potent inhibitor of catecholamine synthesis, reduced both libido and erectile function in sexually mature male rats as it does in humans. In this report, those studies were extended to identify the drug's effect upon catecholamine content in the brain, spinal cord and penile erectile tissue in mature male rats. Because many men report that the adverse effects of alpha-methyldopa upon their sexual performance continue after withdrawal from the drug, a 2nd group of animals was retested after the drug was stopped. Results of the group I study showed diminished copulatory and erectile activity as well as penile and brain norepinephrine content. In the group II rats there was a continued significant reduction in erectile and copulatory activity. At the same time, brain, spinal cord and penile tissue content of norepinephrine returned to normal levels. In another experiment an alpha 2-receptor antagonist was administered with alpha-methyldopa and no inhibition of the effects of alpha-methyldopa was observed. These findings imply that the effect of alpha-methyldopa on sexual function is mediated in the central nervous system as an abnormality of receptor function.
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Louis WJ, Conway E, Summers R, Beart P, Jarrott B. Effects of methyldopa metabolites on amine transmitters and adrenergic receptors in rat brain. Hypertension 1984; 6:II40-4. [PMID: 6094348 DOI: 10.1161/01.hyp.6.5_pt_2.ii40] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Studies of catecholamine concentrations in defined nuclei from the anterior hypothalamic-preoptic regions and the medulla oblongata, known to contribute to cardiovascular control, were measured following acute or chronic methyldopa administration. These studies indicated that methyldopa was enzymatically converted to methyldopamine and methylnorepinephrine, and in some areas to methylepinephrine which replaced endogenous epinephrine. The predominant metabolite was methylnorepinephrine, which accumulated in concentrations higher than endogenous norepinephrine levels. (-)Methylnorepinephrine was found to be 6 times more potent and 75 times more selective for alpha 2-adrenergic receptors than (-) norepinephrine, and it is suggested that this alpha 2-adrenergic receptor action, particularly in the nucleus tractus solitarius, contributes to a major part of the antihypertensive effect of methyldopa.
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Melman A, Libin M, Tendler C. The effect of chronic alpha-methyldopa upon sexual function in the adult male rat. J Urol 1983; 129:643-5. [PMID: 6834569 DOI: 10.1016/s0022-5347(17)52270-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Erectile impotence is a commonly reported undesired side effect in patients treated for hypertension with alpha-methyldopa. However, the mechanism of that dysfunction has not been determined. In this study we report the effect of 12 days of daily intraperitoneal injections, 300 mg./kg., of alpha-methyldopa on adult male, Long-Evans rats and their age-matched saline controls. The effect of the drug upon copulation, penile reflexes and tissue catecholamines was measured. The results showed significant differences between control and experimental animals in all parameters studied. Tests of copulatory ability showed significant decreases in mounts from 5.8 +/- 1.6 (mean +/- standard error) to 3.1 +/- 1.3; penile intromissions from 27.0 +/- 3.8 to 4.8 +/- 1.9; and ejaculations from 2.1 +/- 0.3 to 1.1 +/- 0.6 per 30 minute test period. Penile reflexes measured as erection and cup formation showed similar significant reductions. The norepinephrine content of the penile corpora in the controls was 0.460 +/- 0.084 ng./mg. wet weight and 0.112 +/- 0.022 ng./mg. wet weight in the experimental group. There were similar significant reductions of norepinephrine content in the vas deferens of these animals 32.95 +/- 4.31 ng./mg. and 0.25 +/- 0.1 ng./mg. wet weight in the control and experimental groups respectively.
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Centrally Acting Drugs as a Tool to Study Central Mechanisms of Blood Pressure Control. CURRENT TOPICS IN NEUROENDOCRINOLOGY 1983. [DOI: 10.1007/978-3-642-68490-6_6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Chatelain P, Waelbroeck M, Camus JC, De Neef P, Robberecht P, Roba J, Christophe J. Comparative effects of alpha-methyldopa, propranolol and hydralazine therapy on cardiac adenylate cyclase activity in normal and spontaneously hypertensive rats. Eur J Pharmacol 1981; 72:17-25. [PMID: 6266848 DOI: 10.1016/0014-2999(81)90292-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Normotensive (WKY) and spontaneously hypertensive (SHR) male rats were treated orally, one week after weaning and for 9 weeks, with alpha-methyldopa (100 mg/kg per day), propranolol (30 mg/kg per day) or hydralazine (10 mg/kg per day). Untreated WKY and SHR rats served as controls. The development of hypertension in SHR rats were attenuated by treatment but none of the drugs was able to restore the impairment in isoproterenol, secretin and glucagon responsiveness of cardiac adenylate cyclase activity which is characteristic of these animals. In heart membranes from both WKY and SHR rats, alpha-methyldopa treatment increased the number of beta-adrenoceptors by 20-32% and the maximal response of adenylate cyclase activity to isoproterenol and glucagon by 20-34%. By contrast, the beta-blocker propranolol was ineffective on these parameters. The results obtained are consistent with the hypothesis that the change in adenylate cyclase seen in SHR rats is genetic in origin and is not a consequence of hypertension.
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Mirkin BL, Green TP, O'Dea RF. Disposition and pharmacodynamics of diuretics and antihypertensive agents in renal disease. Eur J Clin Pharmacol 1980; 18:109-16. [PMID: 7398740 DOI: 10.1007/bf00561487] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The pharmacodynamic actions and disposition of diuretic and antihypertensive agents may be significantly modified in subjects with renal disease. Most studies on this question have dealt with alterations in the elimination kinetics of these drugs and, while they generate descriptive data, minimal insight about changes in dose-response relationships or mechanisms of drug action are provided by such investigations. Several basic principles which may serve as useful guidelines in determining how renal failure will influence the response to drugs have been considered. They include the following: degree of renal malfunction, intrinsic toxicity of the drug, alternative pathways for drug metabolism and elimination, elimination pharmacokinetics and dose-response characteristics. Several classes of diuretic agents (thiazides, furosemide) and antihypertensive drugs (hydralazine, methylopda, propranolol, prazosin, and clonidine) have been used as models to define how basic knowledge of renal and non-renal pathways for elimination of drugs and their pharmacodynamic actions may assist in establishing rational therapeutic regimens for these agents in patients with renal failure.
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Evidence for central alpha adrenoceptor stimulation as the basis of paradoxical sleep suppression by alpha methyldopa. Neurosci Lett 1978; 9:37-43. [DOI: 10.1016/0304-3940(78)90045-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/1978] [Accepted: 04/19/1978] [Indexed: 11/24/2022]
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Freed CR, Quintero E, Murphy RC. Hypotension and hypothalamic amine metabolism after long-term alpha-methyldopa infusions. Life Sci 1978; 23:313-22. [PMID: 357873 DOI: 10.1016/0024-3205(78)90015-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Nijkamp FP, De Jong W. Centrally induced hypotension by alpha-methyldopa and alpha-methylnoradrenaline in normotensive and renal hypertensive rats. PROGRESS IN BRAIN RESEARCH 1977; 47:349-68. [PMID: 337354 DOI: 10.1016/s0079-6123(08)62739-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Abstract
Seventy parkinsonian patients were treated continuously with levodopa for five years. During the first year, sixty-three patients (90 per cent) improved. After five years, however, only thirty-seven patients remained improved while thirty-three patients (48 per cent) experienced progressive disease. Complications of treatment, albeit nonfatal, increased in frequency during the five-year interval. The reason for early improvement and subsequent deterioration of parkinsonian symptoms and signs in spite of levodopa therapy remains unexplained. It suggests that Parkinson's disease may not be simply a striatal dopamine deficiency syndrome and that treatment with levodopa is more than replacement therapy.
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Evans PD, Kravitz EA, Talamo BR, Wallace BG. The association of octopamine with specific neurones along lobster nerve trunks. J Physiol 1976; 262:51-70. [PMID: 792417 PMCID: PMC1307630 DOI: 10.1113/jphysiol.1976.sp011585] [Citation(s) in RCA: 111] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Octapamine and its synthetic enzyme, tyramine beta-hydroxylase (TBH), are found in high concentrations at two points along second thoracic nerve roots in lobsters. The first is in the proximal section of the second root between the ventral nerve cord and the bifurcation of the root into medial (to flexor muscles) and lateral (to extensors) branches. The second region of high concentration is within a well known crustacean neurosecretory system, the pericardial organ, located close to the ends of the lateral branches of the roots. 2. With several different staining procedures, small clusters of nerve cell bodies are found within the connective tissue sheath in the proximal regions of the second roots. No cell bodies are seen in the pericardial organ regions. Cell bodies are variable in number and position between corresponding roots in the same animal and homologous roots among different animals. The average numbers of cell bodies, however, correlate well with TBH and octopamine content, and with the synthesis of octopamine in these same regions of roots. 3. Small clusters of root cell bodies dissected from preparations have greater than 500-fold higher activities of TBH than isolated efferent excitatory and inhibitory or afferent sensory axons. 4. Along with octopamine, the preferential synthesis of acetylcholine and serotonin is also seen in proximal segments of roots. Acetylcholine synthesis in these regions may represent transmitter synthesized in the nerve terminals innervating the root cells. The role of serotonin in these regions is not understood at this time but the amounts of endogenous serotonin found are only a tenth of the amounts of octopamine present. 5. Dopamine is not synthesized from tyrosine in second thoracic roots. However, if DOPA or dopamine are used as precursor compounds, then noradrenaline, which is usually not found in lobsters, can be accumulated in proximal segments of roots. 6. Phenolamines are converted to two further metabolites by lobster tissues. The compounds are unidentified and are named fast and slow product on the basis of their migration on electrophoresis at acid pH. Some partial characterization of slow product reveals that it is a mixture of compounds that can be converted on mild acid hydrolysis to fast product and the parent phenolamine. 7. The several lines of evidence presented suggest that nerve cells found in the proximal segments of the second thoracic roots contain and can synthesize octopamine. Since not all the cells in any single root have been analysed for octopamine or TBH, however, the possibility that one or more of the cells contain physiologically interesting substances other than octopamine is not eliminated.
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Dollery CT. Centrally acting alpha-adrenoceptor agonists in hypertension: mechanisms and their role in therapy. AUSTRALIAN AND NEW ZEALAND JOURNAL OF MEDICINE 1976; 6:88-94. [PMID: 1071409 DOI: 10.1111/j.1445-5994.1976.tb03342.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Experimental work in animals has shown that both methyldopa and clonidine lower the blood pressure predominantly by an action on the central nervous system. This action is due to alpha-adrenoceptor stimulation by clonidine and by alpha-methyl-noradrenaline. The evidence for a central site of action for these drugs in man is indirect but persuasive. Both drugs lower blood pressure and heart rate without causing much postural or exercise hypetension. Sympathetic responses like the overshoot of pressure following Valsalva's manoeuvre are reduced but not abolished. Failure of ejaculation in the male is much less common than with drugs that are known to blockade sympathetic adrenergic neurones in the periphery.
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Lo CM, Kwok ML, Wurtman RJ. O-methylation and decarboxylation of alpha-methyldopa in brain and spinal cord: depletion of S-adenosylmethionine and accumulation of metabolites in catecholaminergic neurones. Neuropharmacology 1976; 15:395-402. [PMID: 980218 DOI: 10.1016/0028-3908(76)90116-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Abstract
1. Intraventricular alpha-methyldopamine (50-200 mug) produced a dose-related fall in blood pressure in conscious spontaneously hypertensive rats. Pretreatment with intraventricular 6-hydroxydopamine prevented this hypotensive effect of alpha-methyldopamine. 2. The hypotensive effect of alpha-methyldopamine was prevented by intraventricular injection of phentolamine or desmethylimipramine, but not by intraperitoneal injection of haloperidol. 3. Pretreatment with U-14,624, a selective central dopamine-beta-hydroxylase inhibitor, prevented the hypotensive effect of alpha-methyldopamine. 4. Alpha-methyldopamine was considerably less potent than noradrenaline as a pressor agent in the pithed rat, but noradrenaline and alpha-methylnoradrenaline were found to be equipotent. 5. Alpha-methyldopamine (1-5 mg i.c.v.) reduced pressor responses elicited by electrical stimulation of the midbrain reticular formation in cats anaesthetized with chloralose. 6. It is concluded that the hypotensive action of alpha-methyldopamine in conscious animals involves intact central alpha-adrenergic neurones and a central adrenergic uptake mechanism for the formation of alpha-methylnoradrenaline.
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Ng LK, Kopin IJ. Striatal monoamines and false transmitters. PHARMACOLOGY & THERAPEUTICS. PART B: GENERAL & SYSTEMATIC PHARMACOLOGY 1975; 1:685-94. [PMID: 772714 DOI: 10.1016/0306-039x(75)90024-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Boakes RJ, Candy JM, Wolstencroft JH. Antagonistic actions of alpha-methylnoradrenaline derived from alpha-methyldopa. J Pharm Pharmacol 1973; 25:491-2. [PMID: 4146591 DOI: 10.1111/j.2042-7158.1973.tb09140.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Day MD, Roach AG, Whiting RL. The mechanism of the antihypertensive action of -methyldopa in hypertensive rats. Eur J Pharmacol 1973; 21:271-80. [PMID: 4196583 DOI: 10.1016/0014-2999(73)90126-x] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Finch L, Haeusler G. Further evidence for a central hypotensive action of alpha-methyldopa in both the rat and cat. Br J Pharmacol 1973; 47:217-28. [PMID: 4722038 PMCID: PMC1776563 DOI: 10.1111/j.1476-5381.1973.tb08319.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
1. alpha-Methyldopa (300 mg/kg i.p.) produced a fall in blood pressure in conscious genetic hypertensive rats. Pretreatment with intraventricular 6-hydroxydopamine prevented this hypotensive effect of alpha-methyldopa, whilst intravenous 6-hydroxydopamine reduced but did not prevent the hypotension.2. The hypotensive effect of alpha-methyldopa was prevented or reversed by intraventricular injection of phentolamine (200 mug/rat).3. Pressor responses obtained by stimulation of the entire sympathetic outflow in the Gillespie & Muir preparation, were unaffected by pretreatment with alpha-methyldopa (300 mg/kg i.p.).4. Vasoconstrictor responses to periarterial nerve stimulation of the isolated renal artery preparation of the rat were markedly reduced by pretreatment with alpha-methyldopa. Furthermore, alpha-methylnoradrenaline was found to have one-eighth the vasoconstrictor potency of noradrenaline in this particular artery preparation.5. Pressor responses obtained by stimulation of the posterior hypothalamus or midbrain reticular formation in the rat anaesthetized with urethane were markedly reduced by pretreatment with alpha-methyldopa. FLA-63, a selective dopamine-beta-hydroxylase inhibitor, prevented the reduction of the pressor responses to hypothalamic stimulation produced by alpha-methyldopa.6. Stimulation of the posterior hypothalamus in the anaesthetized cat caused both an increase in sympathetic nerve activity and a rise in blood pressure. These responses were markedly reduced 3-4 h after the injection of alpha-methyldopa (100 mg/kg i.v.).7. These results strongly suggest that the central actions of alpha-methyldopa are important for its hypotensive effect, although a possible peripheral effect cannot be excluded.
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van Zwieten PA. The central action of antihypertensive drugs, mediated via central alpha-receptors. J Pharm Pharmacol 1973; 25:89-95. [PMID: 4146560 DOI: 10.1111/j.2042-7158.1973.tb10599.x] [Citation(s) in RCA: 138] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Heise A, Kroneberg G. Central nervous alpha-adrenergic receptors and the mode of action of alpha-methyldopa. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1973; 279:285-300. [PMID: 4147968 DOI: 10.1007/bf00500607] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Benoy CJ, Elson LA, Schneider R. Multiple emulsions, a suitable vehicle to provide sustained release of cancer chemotherapeutic agents. Br J Pharmacol 1972; 45:135P-136P. [PMID: 5041462 PMCID: PMC1666179 DOI: 10.1111/j.1476-5381.1972.tb09587.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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Mroczek WJ, Leibel BA, Finnerty FA. Comparison of clonidine and methyldopa in hypertensive patients receiving a diuretic. A double-blind crossover study. Am J Cardiol 1972; 29:712-7. [PMID: 4553738 DOI: 10.1016/0002-9149(72)90175-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Fischer JE, James JH. Treatment of hepatic coma and hepatorenal syndrome. Mechanism of action of L-dopa and aramine. Am J Surg 1972; 123:222-30. [PMID: 4401028 DOI: 10.1016/0002-9610(72)90336-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Baldessarini RJ, Vogt M. The uptake and subcellular distribution of aromatic amines in the brain of the rat. J Neurochem 1971; 18:2519-33. [PMID: 4944459 DOI: 10.1111/j.1471-4159.1971.tb00208.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Dhawan BN, Dua PR. Evidence for the presence of -adrenoceptors in the central thermoregulatory mechanism of rabbits. Br J Pharmacol 1971; 43:497-503. [PMID: 4400526 PMCID: PMC1665782 DOI: 10.1111/j.1476-5381.1971.tb07180.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
1. The effects of intracerebroventricular administration of some alpha- and beta-adrenoceptor stimulants and antagonists on the body temperature of rabbits were investigated.2. Noradrenaline produced a dose dependent rise in body temperature. Other catecholamines were less active.3. The noradrenaline response was blocked by alpha-adrenoceptor blocking agents while beta-adrenoceptor antagonists had no effect.4. alpha-Methyl-noradrenaline and metaraminol had some hyperthermic effect, but significantly reduced the response of noradrenaline.5. The possible presence of alpha-adrenoceptors in the central thermoregulatory mechanisms is suggested.
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