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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: enzymes. Br J Pharmacol 2013; 170:1797-867. [PMID: 24528243 PMCID: PMC3892293 DOI: 10.1111/bph.12451] [Citation(s) in RCA: 415] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Enzymes are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, nuclear hormone receptors, catalytic receptors and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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Wu Q, McLeish MJ. Kinetic and pH studies on human phenylethanolamine N-methyltransferase. Arch Biochem Biophys 2013; 539:1-8. [PMID: 24018397 PMCID: PMC3853373 DOI: 10.1016/j.abb.2013.08.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 08/29/2013] [Accepted: 08/31/2013] [Indexed: 02/04/2023]
Abstract
Phenylethanolamine N-methyltransferase (PNMT) catalyzes the conversion of norepinephrine (noradrenaline) to epinephrine (adrenaline) while, concomitantly, S-adenosyl-L-methionine (AdoMet) is converted to S-adenosyl-L-homocysteine. This reaction represents the terminal step in catecholamine biosynthesis and inhibitors of PNMT have been investigated, inter alia, as potential antihypertensive agents. At various times the kinetic mechanism of PNMT has been reported to operate by a random mechanism, an ordered mechanism in which norepinephrine binds first, and an ordered mechanism in which AdoMet binds first. Here we report the results of initial velocity studies on human PNMT in the absence and presence of product and dead end inhibitors. These, coupled with isothermal titration calorimetry and fluorescence binding experiments, clearly shown that hPNMT operates by an ordered sequential mechanism in which AdoMet binds first. Although the logV pH-profile was not well defined, plots of logV/K versus pH for AdoMet and phenylethanolamine, as well as the pKi versus pH for the inhibitor, SK&F 29661, were all bell-shaped indicating that a protonated and an unprotonated group are required for catalysis.
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Affiliation(s)
- Qian Wu
- Department of Medicinal Chemistry, University of Michigan, 428 Church St, Ann Arbor, Michigan 48105
| | - Michael J. McLeish
- Department of Medicinal Chemistry, University of Michigan, 428 Church St, Ann Arbor, Michigan 48105
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 N. Blackford St. Indianapolis, IN 46202
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Warthan MD, Freeman JG, Loesser KE, Lewis CW, Hong M, Conway CM, Stewart JK. Phenylethanolamine N-methyl transferase expression in mouse thymus and spleen. Brain Behav Immun 2002; 16:493-9. [PMID: 12096893 DOI: 10.1006/brbi.2001.0637] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Catecholamines usually are found in neurons and chromaffin cells of mammals. In this study, surprisingly high levels of the epinephrine synthesizing enzyme phenylethanolamine N-methyl transferase (PNMT) were detected in the thymus of young mice. Levels of PNMT activity in the thymus were comparable to levels in the brainstem and were suppressed by the PNMT inhibitor LY134046. PNMT mRNA was localized with in situ hybridization throughout the thymus, but levels were approximately twofold higher in the cortex than in the medulla. PNMT activity was barely detectable in the spleen, and only a few cells expressing PNMT mRNA were located in the marginal zone of the white pulp. These findings suggest that cells in the thymus of young mice have the ability to synthesize epinephrine.
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Affiliation(s)
- Michelle D Warthan
- Department of Biology, Virginia Commonwealth University, Richmond, Virginia 23284, USA
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Gearhart DA, Neafsey EJ, Collins MA. Phenylethanolamine N-methyltransferase has beta-carboline 2N-methyltransferase activity: hypothetical relevance to Parkinson's disease. Neurochem Int 2002; 40:611-20. [PMID: 11900856 DOI: 10.1016/s0197-0186(01)00115-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Mammalian brain has a beta-carboline 2N-methyltransferase activity that converts beta-carbolines, such as norharman and harman, into 2N-methylated beta-carbolinium cations, which are structural and functional analogs of the Parkinsonian-inducing toxin 1-methyl-4-phenylpyridinium cation (MPP+). The identity and physiological function of this beta-carboline 2N-methylation activity was previously unknown. We report pharmacological and biochemical evidence that phenylethanolamine N-methyltransferase (EC 2.1.1.28) has beta-carboline 2N-methyltransferase activity. Specifically, purified phenylethanolamine N-methyltransferase (PNMT) catalyzes the 2N-methylation (21.1 pmol/h per unit PNMT) of 9-methylnorharman, but not the 9N-methylation of 2-methylnorharmanium cation. LY134046, a selective inhibitor of phenylethanolamine N-methyltransferase, inhibits (IC50 1.9 microM) the 2N-methylation of 9-methylnorharman, a substrate for beta-carboline 2N-methyltransferase. Substrates of phenylethanolamine N-methyltransferase also inhibit beta-carboline 2N-methyltransferase activity in a concentration-dependent manner. beta-Carboline 2N-methyltransferase activity (43.7pmol/h/mg protein) is present in human adrenal medulla, a tissue with high phenylethanolamine N-methyltransferase activity. We are investigating the potential role of N-methylated beta-carbolinium cations in the pathogenesis of idiopathic Parkinson's disease. Presuming that phenylethanolamine N-methyltransferase activity forms toxic 2N-methylated beta-carbolinium cations, we propose a novel hypothesis regarding Parkinson's disease-a hypothesis that includes a role for phenylethanolamine N-methyltransferase-catalyzed formation of MPP+ -like 2N-methylated beta-carbolinium cations.
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Affiliation(s)
- Debra A Gearhart
- Department of Cellular Biology and Anatomy, Veterans Affairs Medical Center, Medical College of Georgia, Augusta 30912-2000, USA.
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Beaudouin C, Haurat G, Laffitte JA, Renaud B. The presence of (+)-S-adenosyl-L-methionine in the rat brain and its lack of effect on phenylethanolamine N-methyltransferase activity. J Neurochem 1993; 61:928-35. [PMID: 8360691 DOI: 10.1111/j.1471-4159.1993.tb03604.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
(+)-S-Adenosyl-L-methionine [(+)-SAM] was isolated from rat brain and was quantified by HPLC followed by UV spectrophotometric measurements and by 1H-NMR. Its estimated ratio in brain is 3% of total SAM. Because of its commercial unavailability, (+)-SAM was also prepared from chemically synthesized SAM by separation of the two diastereoisomers on a preparative reverse-phase Nucleosil C8 column. The (+) diastereoisomer thus obtained was then assayed in vitro both as an inhibitor and a substrate of phenylethanolamine N-methyltransferase. Enzymatic activity was measured by HPLC analysis. It was shown that (+)-SAM has no effect on phenylethanolamine N-methyltransferase activity; therefore, it is unlikely that (+)-SAM plays any possible role in regulation of adrenaline synthesis in the brain.
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Affiliation(s)
- C Beaudouin
- Laboratoire de Neuropharmacologie, Faculté de Pharmacie, Université Claude Bernard, Lyon, France
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Beaudouin C, Haurat G, Fraisse L, Souppe J, Renaud B. Assay of phenylethanolamine N-methyltransferase activity using high-performance liquid chromatography with ultraviolet absorbance detection. JOURNAL OF CHROMATOGRAPHY 1993; 613:51-8. [PMID: 8458902 DOI: 10.1016/0378-4347(93)80196-b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A simple and rapid method for measuring phenylethanolamine N-methyltransferase (PNMT) activity by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection is described. This assay requires a partially purified PNMT preparation derived from bovine adrenals, with noradrenaline and S-adenosyl-L-methionine (SAM) as co-substrates. After incubation, the reaction is stopped by addition of acid and the reaction mixture is analysed directly by HPLC. The enzymatically formed S-adenosyl-L-homocysteine (SAH) is detected at 258 nm and determined. Under optimum conditions, the stability of SAH allowed automation of the HPLC detection. This assay was validated by the determination of the kinetic properties of PNMT. Km values for noradrenaline and SAM defined in this assay (16 and 5.7 microM, respectively) are consistent with previously published values. This assay is simple enough to be used for large series of measurements of PNMT activity testing new methyl acceptors, potential inhibitors or PNMT activity in adrenal medulla.
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Affiliation(s)
- C Beaudouin
- Laboratoire de Neuropharmacologie-CNRS UMR 105, Faculté de Pharmacie, Université Claude Bernard, Lyon, France
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7
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Dev BR, Mason PA, Freed CR. Drug-Induced Changes in Blood Pressure Lead to Changes in Extracellular Concentrations of Epinephrine, Dihydroxyphenylacetic Acid, and 5-Hydroxyindoleacetic Acid in the Rostral Ventrolateral Medulla of the Rat. J Neurochem 1992; 58:1386-94. [PMID: 1372344 DOI: 10.1111/j.1471-4159.1992.tb11354.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neurochemical changes in the extracellular fluid of the rostral ventrolateral medulla (RVLM) were produced by changes in arterial blood pressure. Blood pressure was raised or lowered with systemic infusions of phenylephrine or nitroprusside and neurochemicals were recovered from RVLM by in vivo microdialysis. A dialysis probe 300 microns in diameter and 500 microns in length was stereotaxically implanted in the RVLM of the urethane-anesthetized rat. Sterile physiological Ringer's solution was perfused at a rate of 1.5 microliter/min. The perfusate was collected under ice-cold conditions every 15 min for the assay of epinephrine, dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA), ascorbic acid, and uric acid. After stable baseline neurochemical concentrations were achieved, animals were infused with phenylephrine or nitroprusside intravenously to raise or lower the blood pressure. Increasing blood pressure 50 mm Hg above the baseline value by phenylephrine led to a significant reduction in heart rate and a reduction in extracellular epinephrine and DOPAC concentrations. The 5-HIAA concentration was increased during the hypertensive drug infusion. There were no changes in the concentrations of ascorbic acid or uric acid. Hypotension produced by nitroprusside (-20 mm Hg) led to neurochemical changes which were the reciprocal of those seen during hypertension. During hypotension, heart rate increased as did the extracellular fluid epinephrine concentration. The 5-HIAA concentration fell with hypotension and remained depressed following the nitroprusside infusion. Ascorbic acid and uric acid concentrations did not change during hypotension but ascorbic acid did increase after the nitroprusside infusion stopped. These data provide direct evidence that epinephrine release in RVLM is linked to changes in systemic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- B R Dev
- Department of Medicine, University of Colorado Health Sciences Center, Denver 80262
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8
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Rogers PF, Head GA, Lungershausen YK, Howe PR. Effects of depleting central and peripheral adrenaline stores on blood pressure in stroke-prone spontaneously hypertensive rats. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1991; 34:9-16. [PMID: 1940021 DOI: 10.1016/0165-1838(91)90004-m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The potential role of adrenaline, both circulating and in the central nervous system, in the maintenance of high blood pressure was examined in stroke-prone spontaneously hypertensive rats (SHRSP). alpha-Monofluoromethyldopa, a long-lasting inhibitor of dopa decarboxylase, was used to induce rapid depletion of central and peripheral catecholamine stores. Subsequent inhibition of phenylethanolamine-N-methyltransferase (PNMT) allowed the gradual restoration of dopamine and noradrenaline but not adrenaline, resulting in a greater relative depletion of adrenaline. Adrenaline was almost totally depleted in the circulation and peripheral tissues. The resting level of blood pressure, however, was unaffected, excepting after administration of a vasopressin (AVP) antagonist. Moreover, there was no reduction in the magnitude of acute pressor responses to electrical stimulation of the rostral ventrolateral medulla oblongata (C1 area), despite extensive loss of adrenaline from the brainstem and spinal cord. The results suggest that adrenaline contributes to the resting level of blood pressure but that its loss can be offset by the pressor activity of AVP. Thus neither central nor peripheral adrenaline stores appear to be essential for the maintenance of hypertension or for centrally-evoked vasoconstriction in adult SHRSP.
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Affiliation(s)
- P F Rogers
- CSIRO Division of Human Nutrition, Adelaide, SA, Australia
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9
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Opacka-Juffry J, Ruiz de Elvira MC, Tacconelli F, Coen CW. Catecholamine synthesis inhibitors increase pineal adrenaline content by stimulating adrenal medullary activity. Neuroscience 1991; 42:291-7. [PMID: 1861777 DOI: 10.1016/0306-4522(91)90166-l] [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: 12/29/2022]
Abstract
Estimation of noradrenaline and adrenaline utilization in the pineal gland of female rats was attempted using inhibitors of the enzymes that catalyse the catecholamine biosynthetic pathway. Treatment with FLA63, an inhibitor of dopamine beta-hydroxylase (10 mg/kg, 2 h before killing), induced depletion of noradrenaline and adrenaline in the preoptic area and median eminence (sites, respectively, inside and outside the blood-brain barrier) but, paradoxically, resulted in a significant increase (+77%) in the pineal content of adrenaline without affecting that of noradrenaline. Treatment with LY134046, an inhibitor of phenylethanolamine N-methyltransferase (40 mg/kg, 5 and 2 h before killing), induced depletion of adrenaline in the preoptic area and median eminence but, again, resulted in a paradoxical and large increase in pineal adrenaline (+224%); this increase was prevented by prior adrenalectomy. Blood samples taken from free-moving rats fitted with intravenous and intraperitoneal cannulae revealed a marked increase in plasma levels of adrenaline after each injection of LY134046. These results suggest that the adrenal medulla is the primary source for the increase in pineal adrenaline seen after administration of the enzyme inhibitors. The precise site of uptake and the biological implications of this phenomenon remain to be elucidated. Nevertheless, interpretation of in vivo experiments involving these catecholamine synthesis inhibitors should take this adrenal response into account.
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10
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Martensz ND, Goldstone AP, Stuart E, Everitt BJ. Interactions between opioid peptides and adrenaline-containing neurons modulate luteinizing hormone secretion in male rats. J Neuroendocrinol 1990; 2:71-7. [PMID: 19210400 DOI: 10.1111/j.1365-2826.1990.tb00395.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Abstract There is increasing evidence that the opioid inhibition of luteinizing hormone (LH) secretion is mediated, at least in part, by catecholaminergic mechanisms. This study determined the effects of selective manipulation of noradrenergic and adrenergic systems on the ability of opiate receptor blockade to induce the release of LH in adult male rats. Selective depletion of hypothalamic noradrenaline levels by 80% following 6-hydroxydopamine infusions into the central tegmental tract did not alter the 2- to 3-fold increase in serum LH levels following opiate receptor blockade with naloxone (2.5 mg/kg). In contrast, both selective depletion of hypothalamic adrenaline by prior treatment with the phenylethanolamine N-methyltransferase inhibitor, LY134046 (2 x 50 mg/kg) and non-selective depletion of all three catecholamines with alpha-methyl-p-tyrosine (250 mg/kg), abolished the naloxone-induced increase in LH. These results suggest that the inhibition of LH secretion by endogenous opioid peptides is influenced by catecholaminergic neurotransmission and further support the view that adrenaline rather than noradrenaline or dopamine is of importance in this context.
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Affiliation(s)
- N D Martensz
- Department of Anatomy, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK
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Mefford IN, Lister RG, Ota M, Linnoila M. Antagonism of ethanol intoxication in rats by inhibitors of phenylethanolamine N-methyltransferase. Alcohol Clin Exp Res 1990; 14:53-7. [PMID: 2178473 DOI: 10.1111/j.1530-0277.1990.tb00446.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The probable involvement of brain epinephrine in the expression of the acute sedative and intoxicating effects of ethanol and pentobarbital is demonstrated. Two selective inhibitors of phenylethanolamine N-methyltransferase (PNMT), LY134046 and LY78335, proved to be potent and long-lasting antagonists of ethanol intoxication in rats. Acute antagonism of pentobarbital-induced intoxication was observed with LY134046. The present results are compatible with a role for central epinephrine synthesis in ethanol and pentobarbital-induced sedation and intoxication in rats.
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Affiliation(s)
- I N Mefford
- Section on Clinical Pharmacology, National Institute of Mental Health, Bethesda, Maryland 20892
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12
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Durcan MJ, Lister RG, Linnoila M. Behavioral effects of the inhibitors of phenylethanolamine-N-methyltransferase, LY 78335 and LY 134046, and their interactions with ethanol. Psychopharmacology (Berl) 1990; 101:196-202. [PMID: 2349361 DOI: 10.1007/bf02244126] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The centrally active inhibitors of phenylethanolamine-N-methyltransferase (PNMT), LY 78335 and LY 134046, were investigated both alone and in combination with ethanol (2 g/kg) in a holeboard test of directed exploration and locomotor activity. Both PNMT inhibitors showed dose-related reductions in exploratory head-dipping but were without effect on locomotor activity. In combination with ethanol both PNMT inhibitors tended to attenuate the ethanol-induced reductions in exploratory head-dipping but did not effect ethanol's locomotor stimulant properties. LY 134046 showed neither an anxiolytic nor an anxiogenic profile in the plus-maze test of anxiety, nor did it alter the anxiolytic effects of either 1.2 g/kg or 2 g/kg ethanol. LY 134046 did, however, attenuate the ataxic effects of a 2.4 g/kg dose of ethanol. These results may suggest a role for adrenaline synthesis in some, but not all, of the behavioral effects of ethanol.
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Affiliation(s)
- M J Durcan
- Laboratory of Clinical Studies, DICBR, National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD 20892
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Gallo RV, Bona-Gallo A, O'Sullivan D. Adrenergic and noradrenergic regulation of pulsatile luteinizing hormone release. J Neuroendocrinol 1989; 1:157-62. [PMID: 19210448 DOI: 10.1111/j.1365-2826.1989.tb00096.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Abstract The object of this study was to further define the roles of both norepinephrine (NE) and epinephrine (EPIN) in regulating pulsatile luteinizing hormone (LH) release in 4-day ovariectomized rats, in particular to examine the effect of decreasing NE synthesis on pulsatile LH secretion in animals with already greatly depleted levels of brain EPIN. Rats were injected ip with vehicle or drug at -27, -20, -5 and - 3 h relative to the onset of a 3-h blood sampling period. Hypothalamic-preoptic area (HPOA) levels of NE and EPIN were determined by high-performance liquid chromatography. Compared to controls, FLA-63 (25 mg/kg, a dopamine-ss- hydroxylase inhibitor), given at - 3 h, produced 50% and 22% declines in HPOA-NE and EPIN, respectively, and reductions in pulse amplitude and frequency. LY134046 (50 mg/kg, a phenylethanolamine N-methyltransferase inhibitor), given at - 27, - 20 and - 5 h, or -27, -20, -5 and -3 h, produced no change in NE, 88% and 86% declines in EPIN, respectively, and reductions in pulse frequency only. Each LY134046 treatment protocol produced the same decline in EPIN and pulse frequency. Thus, EPIN levels were maximally decreased by three LY134046 injections. When rats were given LY134046 at -27, -20 and -5 h, and FLA-63 at -3 h, compared to rats treated with LY134046 alone, there was no further decrease in HPOA-EPIN (82% decline), a 46% decline in NE, a further reduction in pulse frequency and a reduction in pulse amplitude. This further suppression of LH release must be due to a reduction in HPOA-NE levels since no further decrease in EPIN levels occurred. These data demonstrate within the same animal that NE and EPIN are both stimulatory to pulsatile LH release. NE stimulates the amplitude and frequency, and EPIN stimulates the frequency of pulsatile LH secretion.
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Affiliation(s)
- R V Gallo
- Department of Physiology and Neurobiology, The University of Connecticut, Storrs, Connecticut 06268, USA
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14
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Mallory DS, Bona-Gallo A, Gallo RV. Neurotransmitter involvement in naloxone-induced stimulation of pulsatile LH release on day 8 of pregnancy in the rat. Brain Res Bull 1989; 22:1015-21. [PMID: 2790494 DOI: 10.1016/0361-9230(89)90014-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Naloxone, an endogenous opioid peptide (EOP) receptor antagonist, increases LH pulse frequency and amplitude in early gestation in the rat (7). The object of this study was to further explore the suppression of pulsatile LH release by EOPs on day 8 of pregnancy by examining whether inhibition of norepinephrine (NE) or epinephrine (EPIN) synthesis, or stimulation of gamma-aminobutyric acid (GABA)-B receptors, modified the ability of naloxone infusion (0.5 mg/kg/hr for 3.5 hr) to stimulate pulsatile LH secretion. Blood sampling (50 microliters whole blood/5 min) began 0.5 hr after the onset of infusion. Three studies were conducted. 1) LY 134046 (PNMT inhibitor, 50 mg/kg IP), given at -27, -20, and -3 hr relative to the onset of a 3-hr blood sampling period, produced no change in hypothalamic-preoptic area (HPOA) levels of NE, and a 76% decline in HPOA-EPIN levels, as determined by HPLC. Although basal LH pulse frequency was reduced, this treatment had no effect on the stimulatory action of naloxone on pulsatile LH release. 2) FLA-63 (DBH inhibitor, 25 mg/kg IP) given at -3 hr produced a 72% decline in HPOA-NE levels, a 44% decrease in HPOA-EPIN values, and blocked the stimulatory action of naloxone on LH pulse frequency. Since depletion of HPOA-EPIN by LY 134046 did not compromise the LH response to naloxone, this effect of FLA-63 is due to depletion of HPOA-NE levels. 3) While saline had no effect on the increased pulsatile LH release caused by naloxone, administration of baclofen (GABA-B receptor agonist, 6 mg/kg IV) suppressed the pulsatile LH secretory response to naloxone infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- D S Mallory
- Department of Physiology and Neurobiology, University of Connecticut, Storrs 06269-4154
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15
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Mefford IN, Lawrenz AL, Hsiao JK, Crawley JN. Activation in young rats induced by LY134046, an inhibitor of phenylethanolamine N-methyltransferase. Psychopharmacology (Berl) 1989; 98:240-4. [PMID: 2502794 DOI: 10.1007/bf00444698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
LY134046, a potent, selective inhibitor of rat brain phenylethanolamine N-methyltransferase, was shown to increase activity in 18- and 19-day-old rats. The effects on day 25 were different, with LY134046 causing a decrease in activity. The effects of yohimbine, a selective antagonist of the alpha-2 adrenergic receptor, were markedly different from LY134046, causing a decrease in activity on day 19. These data suggest that epinephrine synthesis may play an inhibitory role in the regulation of activity in young rats.
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Affiliation(s)
- I N Mefford
- Section on Clinical Pharmacology, Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, MD 20892
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16
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Abstract
1. Epinephrine is widely distributed in brains of various species throughout phylogeny but maintains its localization to hypothalamus and brainstem/medulla in all species studied. 2. A general decrease in brain epinephrine content is observed phylogenetically beyond fishes with wide variation within species. 3. The cellular localization of epinephrine forming enzyme is dissociated from epinephrine stores in hypothalamus where epinephrine appears to be primarily a hormone. 4. Three proposed functional pools of epinephrine are described. Synthesis of a hormonal pool and a second, perhaps nonfunctional, pool co-stored in noradrenergic terminals in the forebrain occurs extraneuronally and is probably inhibited acutely in the presence of high corticosteroids due to inhibition of uptake 2. Synthesis of epinephrine in the neuronal pool found primarily in the medulla may be enhanced due to increased PNMT activity in the presence of elevated corticosteroids. 5. Phylogenetic and pharmacological data suggest that epinephrine may play an important role in tonic regulation of the level of arousal, reward and sensitivity to environmental stimuli in mammals.
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Affiliation(s)
- I N Mefford
- Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, Maryland
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Routledge C, Marsden CA. Comparison of the effects of selected drugs on the release of hypothalamic adrenaline and noradrenaline measured in vivo. Brain Res 1987; 426:103-11. [PMID: 2446707 DOI: 10.1016/0006-8993(87)90429-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Intracerebral dialysis combined with high-performance liquid chromatography and electrochemical detection was used to monitor changes in extracellular posterior hypothalamic, noradrenaline, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5-HIAA) following administration of an inhibitor of phenylethanolamine-N-methyltransferase (LY87130); the alpha 2-antagonist idazoxan; the monoamine oxidase (MAO) inhibitor tranylcypromine, and a selective noradrenergic neurotoxin (DSP4) to the anaesthetised rat. LY87130 (50 mg/kg i.p.) decreased basal hypothalamic perfusate and whole-tissue levels of adrenaline by 100% and 64%, respectively, but was without effect on basal extracellular hypothalamic levels and whole-tissue levels of noradrenaline, DOPAC and 5-HIAA. Administration of the alpha 2-adrenoceptor antagonist idazoxan and the MAO inhibitor tranylcypromine elicited increases in hypothalamic extracellular levels of both adrenaline and noradrenaline by 208% and 229%, respectively. Idazoxan also increased hypothalamic extracellular 5-HIAA by 97% but was without effect on extracellular DOPAC. In contrast, tranylcypromine decreased hypothalamic extracellular levels of DOPAC and 5-HIAA by 72% and 50%, respectively. DSP4 depleted extracellular hypothalamic adrenaline and noradrenaline 360 min and 390 min postdrug, respectively, after causing an initial 3-fold increase in both these amines 150 min after drug administration. DSP4 was without effect on posterior hypothalamic extracellular DOPAC and 5-HIAA. These results demonstrate that the pharmacology of central adrenaline and noradrenaline is very similar and, with the exception of phenylethanolamine-N-methyl transferase inhibitors, none of the drugs investigated are able to differentiate between adrenergic and noradrenergic neurones.
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Affiliation(s)
- C Routledge
- Department of Physiology and Pharmacology, Nottingham Medical School, Queens Medical Centre, U.K
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Minson JB, Chalmers JP, Caon AC, Renaud B. Separate areas of rat medulla oblongata with populations of serotonin- and adrenaline-containing neurons alter blood pressure after L-glutamate stimulation. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1987; 19:39-50. [PMID: 2885359 DOI: 10.1016/0165-1838(87)90143-3] [Citation(s) in RCA: 93] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Separate populations of serotonin- and adrenaline-containing neurons exist in the ventrolateral medulla oblongata and project to the intermediolateral cell column of the spinal cord. The medullary serotonin nuclei appear to constitute a heterogeneous group with diverse effects on arterial pressure. Microinjections of sodium glutamate (which excites cell bodies but not axons of passage) made in the area of the ventrolateral serotonin cells evokes an increase in arterial pressure which is abolished by prior 5,7-dihydroxytryptamine (5,7-DHT) treatment. In contrast, glutamate microinjection in the area of the serotonin-containing cell bodies in the midline of the medulla evokes falls in arterial pressure and these responses are attenuated by pretreatment with 5,7-DHT. Glutamate microinjection made in the ventrolateral medulla in the area of the adrenaline-containing cells, evokes increases in arterial pressure which are not altered by 5,7-DHT pretreatment. After ablation of the area of the adrenaline-containing cells by electrolytic lesion, the pressor function of the ventrolateral serotonin-containing cells is still observed. These results suggest that although the serotonin-containing neurons of the ventrolateral medulla are closely aligned with the ventrolateral adrenaline area, the serotonin cell groups and the cells of the adrenaline area exert their pressor actions independently.
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Head GA, Howe PR. Effects of 6-hydroxydopamine and the PNMT inhibitor LY134046 on pressor responses to stimulation of the subretrofacial nucleus in anaesthetized stroke-prone spontaneously hypertensive rats. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 1987; 18:213-24. [PMID: 3106455 DOI: 10.1016/0165-1838(87)90120-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The subretrofacial nucleus of the rostral ventrolateral medulla is an important site for the control of sympathetic vasomotor tone and is the location of the C1 PNMT-containing cell bodies. In the present study the involvement of central monoaminergic neurons in the pressor responses evoked by chemical or electrical stimulation of this nucleus was examined in urethane-anaesthetized stroke-prone spontaneously hypertensive rats (SHRSP). Vehicle-treated rats were compared to animals treated with the PNMT inhibitor LY134046, the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) or a combination of 6-OHDA and the serotonin neurotoxin 5,7-dihydroxytryptamine (5,7-DHT). LY134046 caused a 43% depletion of adrenaline content in the hypothalamus and medulla but not in the spinal cord but had no effect on the pressor responses to stimulation of the subretrofacial nucleus. However, intraventricular administration of 6-OHDA reduced the pressor responses to subretrofacial nucleus stimulation by 50%. 6-OHDA caused profound depletion of noradrenaline in the brain and spinal cord, and adrenaline in the hypothalamus. Combined treatment with 6-OHDA and 5,7-DHT caused the additional depletion of serotonin to 34% and 13% in the hypothalamus and spinal cord, respectively, but caused no further reduction of pressor responses than with 6-OHDA alone. These results suggest that the pressor responses elicited by subretrofacial nucleus stimulation involve a 6-OHDA-sensitive pathway (presumably catecholaminergic) other than the bulbospinal adrenaline pathway but that serotonergic mechanisms do not contribute.
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20
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Connor HE, Drew GM. Do adrenaline-containing neurones from the rostral ventrolateral medulla excite preganglionic sympathetic cell bodies? JOURNAL OF AUTONOMIC PHARMACOLOGY 1987; 7:87-96. [PMID: 2886506 DOI: 10.1111/j.1474-8673.1987.tb00136.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Experiments were performed to investigate whether descending vasomotor neurones from the rostral ventrolateral medulla (RVL) utilize adrenaline as a neurotransmitter. Electrical stimulation of the RVL caused marked, short lasting, reproducible increases in blood pressure and heart rate in anaesthetised atropine methylbromide-treated rats. These effects probably reflect activation of cell bodies rather than fibres of passage since injection of L-glutamate into the same area also produced tachycardia and vasopressor responses. The effects of RVL stimulation were unchanged after bilateral adrenalectomy but were markedly reduced by guanethidine (1 mg/kg, i.v.) suggesting that the tachycardia and vasopressor responses were mediated via increased sympathetic tone to the heart and vasculature. Pretreatment with the phenylethanolamine-N-methyl transferase (PNMT) inhibitor LY134046 (1 mg intracisternally, and 40 mg/kg i.p. daily for 1 day or 5 days) did not modify either the tachycardia or vasopressor response to stimulation of the RVL. Resting blood pressure and heart rate were also unchanged. Cardiac preganglionic sympathetic nerves supplying the heart arise from the C7-T2 region of the spinal cord. Phentolamine and propranolol were injected intrathecally (i.t.) in this region, in an attempt to block the spinal receptors at which any adrenaline, released locally during RVL stimulation, might be expected to act in order to elicit the characteristic tachycardia. Phentolamine (10 and 100 micrograms i.t.) and propranolol (1 microgram i.t.) did not modify the tachycardia but propranolol (10 and 100 micrograms i.t.) caused a dose-dependent reduction. These doses of propranolol (10 and 100 micrograms i.t.) also produced blockade of peripheral beta-adrenoreceptors. The failure of PNMT inhibition to modify the tachycardia or vasopressor response to RVL stimulation and the lack of effect of intrathecally injected alpha-and beta-adrenoreceptor antagonists (at doses which do not exert peripheral effects) against the RVL stimulation-induced tachycardia suggests that adrenaline does not subserve a spinal neurotransmitter role, at the C7-T2 region.
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Limited depletion of central adrenaline stores following administration of adrenaline synthesis inhibitors in rats. Neurochem Int 1987; 10:347-53. [DOI: 10.1016/0197-0186(87)90109-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/1986] [Accepted: 10/24/1986] [Indexed: 11/17/2022]
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COMMUNICATIONS. Br J Pharmacol 1986. [DOI: 10.1111/j.1476-5381.1986.tb14740.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Fuller RW, Hemrick-Luecke SK, Perry KW, Toomey RE. Pergolide elevation of MHPG sulphate concentration in rat hypothalamus blocked by spiperone and mimicked by other dopamine agonists. J Pharm Pharmacol 1985; 37:268-70. [PMID: 2860228 DOI: 10.1111/j.2042-7158.1985.tb05059.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Pergolide increased the concentration of MHPG sulphate (3-methoxy-4-hydroxy-phenylethylene glycol sulphate) in rat hypothalamus, and the increase was prevented by pretreatment with spiperone, a dopamine antagonist. An increase in hypothalamic MHPG sulphate concentration similar to that caused by pergolide was found after injection of quinpirole, a 'partial ergoline' that is a selective D2 agonist not affecting alpha-adrenoceptors, and by (-)-N-propylnorapomorphine, a dopamine agonist not related to the ergolines. Although the increase in MHPG sulphate concentration produced by pergolide had earlier been assumed to result from blockage of alpha-adrenoceptors, the present data indicate that it is an effect produced by dopamine D2 receptor stimulation.
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Studelska DR, Campbell NR, Brimijoin WS. Catecholamine binding by adrenal medullary protein can interfere with a sensitive radioenzymatic assay for norepinephrine. Life Sci 1985; 36:881-7. [PMID: 3974415 DOI: 10.1016/0024-3205(85)90212-7] [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: 01/08/2023]
Abstract
Norepinephrine (NE) binds extensively to protein that copurifies with phenylethanolamine-N-methyltransferase (PNMT) prepared from bovine adrenal medulla. This binding interferes with a NE assay that employs PNMT to catalyze the transfer of a tritiated methyl group from S-adenosyl-L-methionine to the amine group of NE. It was discovered that the protein binding of endogenous NE is reversed by dialysis at pH 6.0. Preparations of PNMT intended for use in radioenzymatic assays should involve one or more purification steps at pH 6.0.
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Tsai SH, Shih CJ, Lin MT. Effects of brain epinephrine depletion on thermoregulation, reflex bradycardia, and motor activity in rats. Exp Neurol 1985; 87:428-38. [PMID: 3972046 DOI: 10.1016/0014-4886(85)90173-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Two hours after i.p. administration of 2-cyclooctyl-2-hydroxyethylamine (CONH), 1-aminomethylcycloundecanol (CUNH), 2,3-dichloro-alpha-methylbenzylamine (DCMB), or 7,8-dichloro-1,2,3,4-tetrahydroisoquinoline (SKF64139), the hypothalamic and brain stem epinephrine (EPI) contents of rat brain were decreased. Depletions of brain EPI with these phenylethanolamine N-methyltransferase (PNMT) inhibitors reduced the rectal temperatures of rats at ambient temperatures of 8 and 22 degrees C. The hypothermia in response to these PNMT inhibitors was due to decreased metabolism and cutaneous vasodilatation. The locomotor stimulant responses induced by thyrotropin-releasing hormone were also reduced by administration of any one of these PNMT inhibitors. On the other hand, acute administration of any of these PNMT inhibitors enhanced the reflex bradycardia induced by i.v. infusion of EPI. The data suggest that brain (particularly the hypothalamus and brain stem) EPI-containing neurons are involved in the regulation of body temperature, reflex bradycardia, and motor performance in the rat.
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Biollaz B, Biollaz J, Kohlman O, Bresnahan M, Gavras I, Gavras H. Acute cardiovascular effects of two central phenylethanolamine-N-methyl-transferase inhibitors in unanesthetized desoxycorticosterone-salt hypertensive rats. Eur J Pharmacol 1984; 102:515-9. [PMID: 6489438 DOI: 10.1016/0014-2999(84)90573-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
SKF 64139, an inhibitor of phenylethanolamine-N-methyltransferase (PNMT), has a marked hypotensive effect in models of sodium-dependent hypertension. The mechanism of this effect is obscure, the compound having in addition alpha-adrenoceptor blocking properties. We compared the acute effects of SKF 64139 with those of LY 134046, another PNMT inhibitor with minimal alpha-blocking capacity, in desoxycorticosterone-salt hypertensive rats. The former agent produced profound hypotension whereas the latter caused only bradycardia. Both induced a similar pronounced suppression of PNMT activity in the C1 and C2 region of the medulla oblongata. These results suggest that the alpha-adrenergic effect rather than PNMT inhibition accounts for the acute lowering of blood pressure in this model.
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Mezey E, Kiss JZ, Skirboll LR, Goldstein M, Axelrod J. Increase of corticotropin-releasing factor staining in rat paraventricular nucleus neurones by depletion of hypothalamic adrenaline. Nature 1984; 310:140-1. [PMID: 6377089 DOI: 10.1038/310140a0] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In response to stress, adrenocorticotropic hormone (ACTH) is released by corticotrophs in the anterior pituitary under the control of several central and peripheral factors including corticotropin-releasing factor (CRF), which was recently isolated from the brain and sequenced. Immunocytochemical studies have shown that most of the CRF-containing cell bodies that project to the median eminence are present in the hypothalamic paraventricular nucleus (PVN). A dense PNMT(phenylethanolamine-N-methyltransferase)-containing fibre network was also observed in the same region--PNMT is the final enzyme in the biosynthesis of adrenaline and has been demonstrated in the brain. In the present study we found an association of adrenergic nerve fibres and CRF neurones by immunohistochemistry using antisera to PNMT and CRF. To examine the functional significance of the adrenergic projection to the PVN, we blocked the synthesis of adrenaline using a specific inhibitor of PNMT. The depletion of adrenaline resulted in an increase in CRF immunoreactivity. The present results suggest that, as well as catecholamines which regulate ACTH release at the anterior pituitary level via a beta 2-adrenergic receptor mechanism, central catecholamines (mainly adrenaline) also affect ACTH release through their action on CRF cells. Peripheral catecholamines seem to have a direct stimulatory effect on the pituitary corticotroph cells, whereas the present findings suggest that central adrenaline-containing neurones have an inhibitory role in the physiological response to stress.
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Vantini G, Perry BD, Guchhait RB, U'Prichard DC, Stolk JM. Brain epinephrine systems: detailed comparison of adrenergic and noradrenergic metabolism, receptor number and in vitro regulation, in two inbred rat strains. Brain Res 1984; 296:49-65. [PMID: 6143593 DOI: 10.1016/0006-8993(84)90510-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Epinephrine content and PNMT activity in medulla pons and hypothalamus of F344 inbred rats is from 3- to 8-fold higher than that of Buf inbred rats. These strain-dependent differences in brain adrenergic neurons are reciprocally related to altered alpha 1- adn alpha 2-adrenergic receptor density in PNMT-containing brain regions. Radioligand binding indices related to alpha 2-receptor function reveal that receptors may be 'desensitized' as well as 'down-regulated' in the strain with high PNMT activity (F344), and may be 'supersensitive' as well as 'up-regulated' in the strain with low PNMT activity (Buf). The association between epinephrine-containing neurons and alpha-adrenergic receptor regulation appears specific, since alpha-adrenergic receptor density and regulation in brain regions devoid of PNMT and epinephrine is similar in F344 and Buf rats. While noradrenergic metabolism in F344 rats is greater than that in Buf rats, this difference is generalized throughout the brain and, thus, bears no apparent relationship to the localized alterations in alpha-adrenergic receptor density. Moreover, beta-adrenergic receptor density in the 2 strains is similar in all brain regions. These data suggest that a significant proportion of alpha-adrenergic receptors in medulla-pons and hypothalamus are intimately related to and regulated by epinephrine-containing nerve endings.
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Abstract
Dopamine (DA), norepinephrine (NE), and epinephrine (EPI) are present in rat retina. DA is the major catecholamine, whereas NE and EPI represent approximately 5% of the DA content. DA is contained in a subpopulation of amacrine cells and has been the subject of numerous studies. We investigated the origin and properties of NE and EPI in retina. Following superior cervical ganglionectomy, there was a decrease in NE content, but no decrease in EPI or phenylethanolamine-N-methyltransferase (PNMT) activity. PNMT in retina has many of the substrate-specificity and inhibitor-sensitivity characteristics of other tissues. Enzyme activity is enhanced in newborn rats by treatment with dexamethasone. Exposure to a lighted environment increases retinal EPI in normal and superior cervical ganglionectomized rats. EPI content increased for more than 2 h in a lighted environment. We conclude that most of the NE is contained within the sympathetic neurons that innervate the eye from the superior cervical ganglion, whereas EPI is contained in retinal elements that are responsive to photic stimulation.
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Beart PM, Rowe PR, Louis WJ. alpha-Methyladrenaline is a central metabolite of alpha-methyldopa. J Pharm Pharmacol 1983; 35:519-20. [PMID: 6137538 DOI: 10.1111/j.2042-7158.1983.tb04822.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Sangdee C, Franz DN. Evidence for inhibition of sympathetic preganglionic neurons by bulbospinal epinephrine pathways. Neurosci Lett 1983; 37:167-73. [PMID: 6308523 DOI: 10.1016/0304-3940(83)90148-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Two selective inhibitors of central epinephrine synthesis, LY 134046 and SKF 64139 (20 mg/kg, i.v.), gradually but markedly enhanced descending intraspinal transmission to sympathetic preganglionic neurons in spinal cats. Enhancement increased linearly to maximum values of 200% and 250%, respectively, at 4.5-5.5 h. Spinal sympathetic reflexes were not enhanced by either drug. The results support the proposal that bulbospinal epinephrine pathways depress the excitability of sympathetic preganglionic neurons by activating postsynaptic alpha 2-adrenergic receptors.
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Fuller RW, Hemrick-Luecke SK, Perry KW. Inhibition of brain epinephrine synthesis by 3,4-dichlorophenylethanolamine, a competitive substrate for norepinephrine N-methyltransferase. Biochem Pharmacol 1983; 32:215-20. [PMID: 6870951 DOI: 10.1016/0006-2952(83)90546-4] [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: 01/22/2023]
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Bondinell WE, Chapin FW, Frazee JS, Girard GR, Holden KG, Kaiser C, Maryanoff C, Perchonock CD, Gessner GW, Hieble JP. Inhibitors of phenylethanolamine N-methyltransferase and epinephrine biosynthesis: a potential source of new drugs. Drug Metab Rev 1983; 14:709-21. [PMID: 6352222 DOI: 10.3109/03602538308991406] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Fuller RW, Hemrick-Luecke SK. Methylation of norepinephrine and alpha-methylnorepinephrine in brain. Biochem Pharmacol 1982; 31:3128-30. [PMID: 6756412 DOI: 10.1016/0006-2952(82)90094-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Toomey RE, Horng JS, Hemrick-Luecke SK, Fuller RW. alpha 2 Adrenoreceptor affinity of some inhibitors of norepinephrine N-methyltransferase. Life Sci 1981; 29:2467-72. [PMID: 6119595 DOI: 10.1016/0024-3205(81)90701-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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