451
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Hall H, Wedel I, Halldin C, Kopp J, Farde L. Comparison of the in vitro receptor binding properties of N-[3H]methylspiperone and [3H]raclopride to rat and human brain membranes. J Neurochem 1990; 55:2048-57. [PMID: 1977888 DOI: 10.1111/j.1471-4159.1990.tb05794.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The aim of the present investigation was to study and compare the in vitro binding properties of the two radioligands N-[3H]methylspiperone ([3H]NMSP) and [3H]raclopride. These compounds, labeled with 11C, have been extensively used in positron emission tomography studies on central dopamine D2 receptors in schizophrenic patients, although with diverging results. One study (using [11C]NMSP) showed an increased dopamine receptor density in drug-naive schizophrenic patients, whereas in another study (using [11C]raclopride) the density in schizophrenic patients was no different from that in healthy controls. In the present study, using in vitro binding techniques, the density of the binding sites was found to be similar irrespective of which of the two radioligands was used (20 fmol/mg wet weight in rat striatum and 10 fmol/mg in human putamen; the 5-hydroxytryptamine 2 receptors were blocked with 40 nM ketanserin). [3H]NMSP had a 10-fold higher affinity (KD, 0.3 nM in rat striatum and 0.2 nM in human putamen) than [3H]raclopride (KD, 2.1 nM in rat striatum and 3.9 nM in human putamen), which was consistent with the longer dissociation half-life of [3H]NMSP compared with [3H]raclopride (14.8 and 1.19 min, respectively). There was an approximate overall similarity between the inhibition constants for five dopamine antagonists, chlorpromazine, haloperidol, raclopride, remoxipride, and NMSP, when using either radioligand. The Ki values were, however, two- to four-fold higher when using [3H]NMSP as the radioligand, irrespective of inhibiting compound, except for chlorpromazine (and haloperidol in human putamen). NMSP was found to inhibit the binding of [3H]raclopride competitively, whereas raclopride inhibited the binding of [3H]NMSP both competitively and noncompetitively. This difference suggests that part of the binding site is exclusively used by NMSP and can only be allosterically interfered with by raclopride. It is proposed that [3H]NMSP binds to an additional set of accessory binding sites, presumably located more distantly from the agonist binding active site than the sites to which [3H]raclopride binds.
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Affiliation(s)
- H Hall
- CNS2 Research and Development, Neuropharmacology, Astra Research Centre AB, Södertälje, Sweden
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452
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Brodde OE. Subclassification of peripheral dopamine receptors. JOURNAL OF AUTONOMIC PHARMACOLOGY 1990; 10 Suppl 1:s5-9. [PMID: 2098376 DOI: 10.1111/j.1474-8673.1990.tb00221.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
1. There is convincing evidence to suggest that two DA-receptor subtypes exist in the periphery, that can at best be differentiated by the potency of the antagonists SCH 23390 and domperidone: at DA-1 receptors the order of potency is SCH 23390 much greater than domperidone, at DA-2 receptors it is domperidone much greater than SCH 23390. 2. As in the adrenergic, muscarinic or 5-HT-receptor field, future studies employing both molecular biology and pharmacological approaches will show whether such a subclassification is sufficient to explain all peripheral effects of DA or whether DA-1 and DA-2 receptors have to be subdivided into further subtypes.
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Affiliation(s)
- O E Brodde
- Biochemisches Forschungslabor, Medizinische Klinik, Universitätsklinikum Essen, Germany
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453
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Tsuchida K, Shigemoto R, Yokota Y, Nakanishi S. Tissue distribution and quantitation of the mRNAs for three rat tachykinin receptors. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 193:751-7. [PMID: 1701145 DOI: 10.1111/j.1432-1033.1990.tb19396.x] [Citation(s) in RCA: 144] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The family of mammalian tachykinin receptors consists of substance P receptor (SPR), neuromedin K receptor (NKR) and substance K receptor (SKR). In this investigation, tissue and regional distributions of the mRNAs for the three rat tachykinin receptors were investigated by blot-hybridization and RNase-protection analyses using the previously cloned receptor cDNAs. SPR mRNA is widely distributed in both the nervous system and peripheral tissues and is expressed abundantly in the hypothalamus and olfactory bulb, as well as in the urinary bladder, salivary glands and small and large intestines. In contrast, NKR mRNA is predominantly expressed in the nervous system, particularly in the cortex, hypothalamus and cerebellum, whereas SKR mRNA expression is restricted to the peripheral tissues, being abundant in the urinary bladder, large intestine, stomach and adrenal gland. Thus, the mRNAs for the three tachykinin receptors show distinct patterns of expression between the nervous system and peripheral tissues. Blot-hybridization analysis in combination with S1 nuclease protection and primer-extension analyses revealed that there are two large forms of SKR mRNA expressed commonly in the peripheral tissues, and two additional small forms of the mRNA expressed specifically in the adrenal gland and eye. These analyses also showed that the multiple forms of SKR mRNA differ in the lengths of the 5' mRNA portions, and that the two small forms of the mRNA, if translated, encode a truncated SKR polypeptide lacking the first two transmembrane domains. This investigation thus provides the comprehensive analysis of the distribution and mode of expression of the mRNAs for the multiple peptide receptors and offers a new basis on which to interpret the diverse functions of multiple tachykinin peptides in the CNS and peripheral tissues.
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Affiliation(s)
- K Tsuchida
- Institute for Immunology, Kyoto University Faculty of Medicine, Japan
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454
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Jose PA, Felder RA, Felder CC, Chan WY. Molecular biology of adrenergic and dopamine receptors and the study of developmental nephrology. Pediatr Nephrol 1990; 4:679-85. [PMID: 1982417 DOI: 10.1007/bf00858648] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Neurotransmitters convey specific messages by binding to receptors on the cell membrane surface. Receptors are linked to membrane-bound, signal-transducing proteins which act as intermediaries in the generation of second messengers that elicit biological responses. Cell surface receptors could be grouped into families that utilize common systems for their signal transmission. These classes include the growth factor receptors, the transporter receptors which internalize their ligands, ion channels, and G-protein-coupled receptors. In the past few years, the cDNAs and/or genes of a number of G-protein-coupled receptors have been cloned. Structural analysis of the G-protein-coupled receptors, as well as the other classes of receptor, shows that those receptors which use a common signaling pathway have similar topographies and share significant sequence homology. Adrenergic and dopamine receptors are examples of receptors coupled to G proteins. This review outlines some strategies in the study of adrenergic and dopamine receptors using molecular biology techniques and how they relate to investigations in developmental nephrology.
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Affiliation(s)
- P A Jose
- Department of Pediatrics, Georgetown University Medical Center, Washington, DC 20007-2197
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455
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Enjalbert A, Guillon G, Mouillac B, Audinot V, Rasolonjanahary R, Kordon C, Bockaert J. Dual mechanisms of inhibition by dopamine of basal and thyrotropin-releasing hormone-stimulated inositol phosphate production in anterior pituitary cells. Evidence for an inhibition not mediated by voltage-dependent Ca2+ channels. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(17)30586-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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456
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John MacLennan A, Frantz GD, Weatherwax RC, Tillakaratne NJ, Tobin AJ. Expression of mRNAs that encode D2 dopamine receptor subtypes: Anatomical, developmental, and pharmacological studies. Mol Cell Neurosci 1990; 1:151-60. [DOI: 10.1016/1044-7431(90)90020-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/21/1990] [Indexed: 10/20/2022] Open
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457
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Coirini H, Schumacher M, Angulo JA, McEwen BS. Increase in striatal dopamine D2 receptor mRNA after lesions of haloperidol treatment. Eur J Pharmacol 1990; 186:369-71. [PMID: 2127022 DOI: 10.1016/0014-2999(90)90464-h] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- H Coirini
- Laboratory of Neuroendocrinology, Rockefeller University, New York, NY 10021
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458
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Sokoloff P, Giros B, Martres MP, Bouthenet ML, Schwartz JC. Molecular cloning and characterization of a novel dopamine receptor (D3) as a target for neuroleptics. Nature 1990; 347:146-51. [PMID: 1975644 DOI: 10.1038/347146a0] [Citation(s) in RCA: 1953] [Impact Index Per Article: 57.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A dopamine receptor has been characterized which differs in its pharmacology and signalling system from the D1 or D2 receptor and represents both an autoreceptor and a postsynaptic receptor. The D3 receptor is localized to limbic areas of the brain, which are associated with cognitive, emotional and endocrine functions. It seems to mediate some of the effects of antipsychotic drugs and drugs used against Parkinson's disease, that were previously thought to interact only with D2 receptors.
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Affiliation(s)
- P Sokoloff
- Unité de Neurobiologie et Pharmacologie (U. 109) de l'INSERM, Paris, France
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459
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Monsma FJ, Mahan LC, McVittie LD, Gerfen CR, Sibley DR. Molecular cloning and expression of a D1 dopamine receptor linked to adenylyl cyclase activation. Proc Natl Acad Sci U S A 1990; 87:6723-7. [PMID: 2168556 PMCID: PMC54609 DOI: 10.1073/pnas.87.17.6723] [Citation(s) in RCA: 298] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In order to clone the D1 dopamine receptor linked to adenylyl cyclase activation, the polymerase chain reaction was used with highly degenerate primers to selectively amplify a cDNA sequence from NS20Y neuroblastoma cell mRNA. This amplification produced a cDNA fragment exhibiting considerable sequence homology to guanine nucleotide-binding (G)-protein-coupled receptors that have been cloned previously. To characterize this cDNA further, a full-length clone was isolated from a rat striatal library by using the cDNA fragment as a probe. Sequence analysis of this cDNA clone indicated that it is indeed a member of the G-protein-coupled receptor family and exhibits greatest homology with the previously cloned catecholamine receptors. Northern blot analysis of various neural tissues revealed a transcript of approximately 4 kb that was predominantly located in the striatum with lesser amounts in the cortex and retina. In contrast, no mRNA was detected in the cerebellum, hippocampus, olfactory bulb, mesencephalon, or pituitary. In situ hybridization analysis also revealed a high abundance of mRNA in the striatum as well as in the olfactory tubercle. To establish the identity of this cDNA, we performed transient expression experiments in COS-7 cells. [3H]SCH-23390, a D1-selective radioligand, exhibited specific, saturable binding only in cells that were transfected with this cDNA. Competition binding analysis with a variety of dopaminergic ligands demonstrated a D1 dopaminergic pharmacology. In addition, dopamine as well as other D1-selective agonists stimulated cAMP accumulation in transfected COS-7 cells. We conclude that we have cloned a cDNA encoding the D1 dopamine receptor linked to the activation of adenylyl cyclase activity.
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Affiliation(s)
- F J Monsma
- Experimental Therapeutics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892
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460
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Srivastava LK, Morency MA, Bajwa SB, Mishra RK. Effect of haloperidol on expression of dopamine D2 receptor mRNAs in rat brain. J Mol Neurosci 1990; 2:155-61. [PMID: 1703431 DOI: 10.1007/bf02896840] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Chronic administration of the neuroleptic drug haloperidol previously has been shown to increase the density of striatal dopamine D2 receptor, which is believed to be the underlying factor in neuroleptic-induced tardive dyskinesia. To search for the mechanism of receptor upregulation, the expression of the isoforms of dopamine D2 receptor mRNA in rat striatum was analyzed by Northern, solution, and in situ hybridizations in haloperidol-treated rats (1-35 days). Northern blot analysis of poly(A)+ RNA hybridized with a probe common for both isoforms as well as an insert-specific probe for the long isoform of the receptor revealed no significant difference in hybridization signal between the control and any of the haloperidol-treated groups of rats. The receptor density, however, was increased by 30-40% in animals receiving haloperidol for 7-35 days. Solution hybridization with an antisense riboprobe specific for a consensus sequence as well as in situ hybridization with a consensus oligonucleotide probe similarly failed to detect any increase in the expression of receptor mRNA following haloperidol treatment. The results suggest that post-transcriptional mechanisms may be responsible for regulating the haloperidol-induced increase in dopamine D2 receptors.
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Affiliation(s)
- L K Srivastava
- Department of Psychiatry, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada
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461
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Abstract
This review will focus on the main lines of evidence that suggest the existence of multiple types of dopamine D-2 receptors. Dopamine D-2 receptors share structural elements suggesting that they belong to a gene superfamily classified as G-protein-coupled receptors and show an archetypical topology predicted to consist of seven putative transmembrane domains. Activation of D-2 receptors results in a variety of responses, including inhibition of cyclic AMP formation, inhibition of phosphoinositol turnover, increase of K-channel activity, and inhibition of Ca influx. The G protein(s) linking the D-2 receptors to these responses have not been completely identified, nor has the possible hierarchy of these regulatory proteins in transforming the incoming signal into a change of second-messenger levels. A lot of experimental data support the hypothesis that there are multiple signal-processing pathways activated by dopamine through D-2-receptor stimulation. Recently, the identification of dopaminergic drugs that discriminate among the different transduction pathways and the isolation of distinct cDNAs encoding proteins that share binding profile indicative of D-2 receptors clearly indicate multiple forms of D-2 receptors. Pharmacologically, at least two distinct categories of dopamine D-2 receptors exist in rat pituitary. The first (D-2a) is insensitive to BHT 920 and coupled to inhibition of adenylyl cyclase activity; the second (D-2b) is activated by BHT 920 and linked to voltage-dependent K channels. The two types of dopamine D-2 receptors differ in their structure, G-protein-coupled and effector. Each of the three basic receptor units shows a certain degree of heterogeneity, which may affect the quality and the kinetic of the response. This variety may represent the molecular basis for the diversity in pharmacological and functional profiles of different dopamine D-2 receptors located in various brain areas and peripheral tissues.
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Affiliation(s)
- M Memo
- Department of Biomedical Sciences and Biotechnologies, School of Medicine, University of Brescia, Italy
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462
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Abstract
Significant new information on the D2 dopamine receptor has recently become available from a combination of protein chemical and molecular genetic analyses. Molecular genetic studies have shown the receptor to be a member of the family of receptors that are linked to G proteins and that have structures predicted to contain seven transmembrane domains. Two distinct species of D2 dopamine receptor have been found which may differ in their coupling to G proteins; their distributions have been mapped at the nucleic acid level. The D2 dopamine receptor has been purified from brain and anterior pituitary and characterized. Chemical modification of the brain receptor provides evidence for the importance of a carboxyl group that interacts with ligands at the receptor binding site. Here, Philip Strange discusses these points and proposes models of receptor-ligand interaction based on the conservation of several aspartic acid residues in receptors that bind cationic amines.
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Affiliation(s)
- P G Strange
- Biological Laboratory, University Canterbury, UK
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463
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Wright MS, Karlsen HE, Paulssen EJ, Meyerhof W, Høgset A, Gautvik KM. Different-sized mRNAs from GH4C1 cells induce a TRH-dependent electrical response in Xenopus laevis oocytes. ACTA PHYSIOLOGICA SCANDINAVICA 1990; 140:129-34. [PMID: 2177312 DOI: 10.1111/j.1748-1716.1990.tb08983.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Poly(A)+ RNA from the GH4C1 rat pituitary cell line elicited a thyrotropin releasing hormone response in Xenopus laevis oocytes which could be measured as a change in membrane current by the voltage-clamp method. Oocytes injected with Poly(A)+ RNA from GH12C1 cells which do not bind thyrotropin releasing hormone or with buffer solution alone did not show this response. Size fractionation of total poly(A)+ RNA by sucrose density-gradient centrifugation shows two response maximal representing various mRNA fractions larger than 18S. These results indicate the presence of thyrotropin releasing hormone receptor mRNA heterogeneity where the smallest mRNA is at least 2 kb.
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Affiliation(s)
- M S Wright
- Institute of Medical Biochemistry, University of Oslo, Norway
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464
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Affiliation(s)
- M E Wolf
- Department of Psychiatry, Wayne State University School of Medicine, Lafayette Clinic, Detroit, Michigan 48207
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465
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Andersen PH, Gingrich JA, Bates MD, Dearry A, Falardeau P, Senogles SE, Caron MG. Dopamine receptor subtypes: beyond the D1/D2 classification. Trends Pharmacol Sci 1990; 11:231-6. [PMID: 2200181 DOI: 10.1016/0165-6147(90)90249-8] [Citation(s) in RCA: 214] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The D1/D2 dopamine receptor classification is widely accepted. However, intense investigative efforts over the last several years using pharmacological, biochemical and behavioral approaches have produced results that are increasingly difficult to reconcile with the existence of only two dopamine receptor subtypes. Recent developments, including cloning of the cDNAs and/or genes for several members of the large family of G-protein-coupled receptors, have revealed that heterogeneity in the pharmacological or biochemical characteristics of individual receptors often indicates the presence of previously unsuspected molecular subtypes. In this article, Marc Caron and colleagues have assembled the main lines of evidence that suggest the presence of several novel subtypes for both D1 and D2 dopamine receptors and predict that molecular cloning will, in the near future, confirm their existence.
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Affiliation(s)
- P H Andersen
- Novo Nordisk A/S, CNS Division, Bagsvaerd, Denmark
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466
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Nakayama K, Pattanakitsakul S, Yokoyama S, Kimura H, Nonaka M, Takahashi M. Post-transcriptional regulation of complement C4 in low C4-producing strain of mouse. Immunogenetics 1990; 31:361-7. [PMID: 2370081 DOI: 10.1007/bf02115011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The expression of the fourth component of complement (C4) of the mouse can differ 20-fold and is determined by C4-high (C4h) or C4-low (C4l) alleles. To investigate the molecular mechanisms underlying the differences in C4 expression, we compared the transcriptional activity of the C4 genes between high and low C4-producer strains of mice (B10 and FM vs B10.BR) using nuclear transcriptional and chloramphenicol acetyltransferase (CAT) assays. We also compared the level of C4-specific RNA in total and nuclear RNA of the liver. The results revealed no significant difference in transcriptional activity between C4h and C4l genes. However, the steady-state levels of C4 mRNA are ten times lower in C4l strains than in C4h strains, suggesting that the major regulation of C4 plasma levels occurs at the post-transcriptional level.
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Affiliation(s)
- K Nakayama
- Department of Immunobiology, Kanazawa University, Japan
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467
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Mahan LC, Burch RM, Monsma FJ, Sibley DR. Expression of striatal D1 dopamine receptors coupled to inositol phosphate production and Ca2+ mobilization in Xenopus oocytes. Proc Natl Acad Sci U S A 1990; 87:2196-200. [PMID: 1690425 PMCID: PMC53653 DOI: 10.1073/pnas.87.6.2196] [Citation(s) in RCA: 132] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Expression of central nervous system receptors for dopamine was examined by injection of poly(A)+ RNA (mRNA) from rat striatum into oocytes from Xenopus laevis. Electrophysiological measurements in mRNA-injected oocytes indicated that addition of 100 microM dopamine induced an inward current (40-100 nA) that was consistent with the activation of endogenous Ca2(+)-dependent Cl- channels. This current was also elicited by addition of the selective D1 agonist SKF 38393 but not by the selective D2 agonist quinpirole. Prior addition of the dopaminergic antagonist cis-piflutixol completely abolished dopamine-induced currents but had no effect on currents produced by serotonin. Using 45Ca2+ efflux assays, addition of 100 microM dopamine to injected oocytes stimulated efflux 2- to 3-fold. This increase was mimicked by SKF 38393 and was blocked by the D1-selective antagonist (+)SCH 23390 but not by the D2-selective antagonist domperidone. No increase in 45Ca2+ efflux was seen with 100 microM quinpirole. Size fractionation of striatal mRNA yielded a single peak (2.5-3.0 kilobases) of D1 receptor-mediated 45Ca2+ efflux activity in injected oocytes. In addition, dopamine stimulation of oocytes injected with peak fractions and prelabeled with myo-[3H]inositol caused a 3-fold increase in [3H]inositol 1,4,5-triphosphate [( 3H]InsP3) formation. No effect on [3H]InsP3 production or 45Ca2+ efflux was observed, however, in injected oocytes incubated with 1 mM N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate. Thus, in addition to D1 receptors that stimulate adenylyl cyclase, rat striatum contains D1 receptors that can couple to InsP3 formation and mobilization of intracellular Ca2+.
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Affiliation(s)
- L C Mahan
- Laboratory of Cell Biology, National Institute of Mental Health, National Institutes of Health, Bethesda, MD
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468
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Chapter 1. Novel Antipsychotic Agents. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1990. [DOI: 10.1016/s0065-7743(08)61577-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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469
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Abstract
The aims of this study were two-fold. Firstly, to characterize the behavioral properties of a potential new dopamine D1 receptor agonist, (-)-4,6,6a,7,8,12b-hexahydro-7-methyl-indolo[4,3-ab]phenanth ridine (CY 208-243), to determine its suitability as a tool for investigating D1 receptor function in vivo. Secondly, to investigate how the behavioural properties of D1 agonists are modified in the presence of D2 receptor blocking drugs. For this purpose, using mice, we employed CY 208-243 and 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine hydrochloride (SKF 38393) as reference D1 agonists, and the substituted benzamides metoclopramide and sulpiride as selective D2 antagonists. CY 208-243 (0.25-10 mg/kg) caused only a modest increase in grooming in non-habituated mice, but stimulated locomotion, rearing, grooming and orofacial activities in habituated animals. These responses were inhibited by a D1 antagonist, but not by D2 antagonists, suggesting CY 208-243 behaves as a selective agonist of D1 receptors in vivo. In non-habituated mice, doses of metoclopramide and sulpiride which had little or no effect on motor behaviour by themselves, interacted synergistically with CY 208-243 (4 mg/kg) and SKF 38393 (30 mg/kg) to cause extended periods of immobility. Other species-typical behaviours were not affected in this way. For example, grooming was decreased by metoclopramide and increased by sulpiride, indicating that an increase in behavioural competition from this parameter was not the cause of the hypokinesia. To explain the apparent ability of D1 receptor stimulation to increase exploratory activity in earlier experiments and to decrease it here, it is proposed that this behaviour is regulated by D1 receptors coupled to two functionally opposite postsynaptic D2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- C J Chandler
- School of Health and Human Sciences, Hatfield Polytechnic, Hertfordshire, U.K
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470
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Arbuthnott GW, Fairbrother IS, Butcher SP. Dopamine release and metabolism in the rat striatum: an analysis by 'in vivo' brain microdialysis. Pharmacol Ther 1990; 48:281-93. [PMID: 2128125 DOI: 10.1016/0163-7258(90)90050-c] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Brain microdialysis studies on the mechanisms underlying dopamine release in the rat striatum provide evidence that both exocytotic and carrier-dependent processes operate in vivo. While several releasers (potassium, veratrine, amphetamine, ouabain) utilize newly synthesized stores of dopamine, tyramine is uniquely sensitive to depletion of vesicular storage by reserpine. Extracellular DOPAC is closely associated with the newly synthesized pool of dopamine and experiments with selective monoamine oxidase inhibitors suggest that DOPAC is formed mainly by MAO-A. Recent work on the two dopamine receptors suggest that release by different mechanisms may selectively activate D1 or D2 receptor subtypes.
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Affiliation(s)
- G W Arbuthnott
- Department of Preclinical Veterinary Sciences, University of Edinburgh, Summerhall, U.K
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471
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