A. L. Hudson, E. S. J. Robinson, M. D. Lalies, R. J. Tyacke, H. C. Jackson, D. J. Nutt
{"title":"In vitro and in vivo approaches to the characterization of the α2-adrenoceptor","authors":"A. L. Hudson, E. S. J. Robinson, M. D. Lalies, R. J. Tyacke, H. C. Jackson, D. J. Nutt","doi":"10.1111/j.1365-2680.1999.tb00003.x","DOIUrl":null,"url":null,"abstract":"<div>\n \n <p><b>1</b> In order to more fully understand the role of the α<sub>2</sub>-adrenoceptor in brain function, a combination of <i>in vitro</i> and <i>in vivo</i> techniques were utilized including radioligand binding, autoradiography, brain microdialysis and antisense oligonucleotides.</p>\n <p><b>2</b> Binding studies showed the tritiated form of the selective α<sub>2</sub>-adrenoceptor antagonist, RX821002 (methoxy-idazoxan) labelled an apparent single population of sites in rat brain membranes with high affinity (1 nM), for which prazosin had low affinity (1107 nM). Similar studies in rabbit brain membranes found that prazosin and oxymetazoline were able to displace. [<sup>3</sup>H]-RX821002 in a biphasic manner indicating the presence of subtypes of α<sub>2</sub>-adrenoceptors.</p>\n <p><b>3</b> Receptor autoradiography revealed a distribution of [<sup>3</sup>H]-RX821002 binding in rat brain consistent with the labelling of all %aL<sub>2</sub>-adrenoceptor subtypes, namely α<sub>2A/D</sub>-, α<sub>2B</sub> and α<sub>2C</sub>.</p>\n <p><b>4</b> In rat, <i>in vivo</i> brain dialysis experiments demonstrated peripherally administered RX821002 elevated basal noradrenaline in frontal cortex and also, although to a lesser extent, in ventral hippocampus. RX821002 was also able to elevate extracellular dopamine in the striatum.</p>\n <p><b>5</b> A 7-day i.c.v. infusion of an antisense oligonucleotide targeting the α<sub>2A/D</sub>-adrenoceptor, resulted in a significant reduction in the autoradiographic density of [<sup>3</sup>H]-RX821002 binding in specific brain areas, notably the lateral septal nuclei and anterior hypothalamic area.</p>\n <p><b>6</b> Several years of research by our group has extended our knowledge of the pharmacology and function of the α<sub>2</sub>-adrenoceptor and has provided evidence of the roles of this receptor in the control of monoamine turnover. The successful use of antisense technology to knockdown expression of the α<sub>2A/D</sub> subtype provides future opportunities to explore the physiology of this receptor subtype.</p>\n </div>","PeriodicalId":100151,"journal":{"name":"Autonomic and Autacoid Pharmacology","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2009-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/j.1365-2680.1999.tb00003.x","citationCount":"28","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Autonomic and Autacoid Pharmacology","FirstCategoryId":"1085","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2680.1999.tb00003.x","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 28
Abstract
1 In order to more fully understand the role of the α2-adrenoceptor in brain function, a combination of in vitro and in vivo techniques were utilized including radioligand binding, autoradiography, brain microdialysis and antisense oligonucleotides.
2 Binding studies showed the tritiated form of the selective α2-adrenoceptor antagonist, RX821002 (methoxy-idazoxan) labelled an apparent single population of sites in rat brain membranes with high affinity (1 nM), for which prazosin had low affinity (1107 nM). Similar studies in rabbit brain membranes found that prazosin and oxymetazoline were able to displace. [3H]-RX821002 in a biphasic manner indicating the presence of subtypes of α2-adrenoceptors.
3 Receptor autoradiography revealed a distribution of [3H]-RX821002 binding in rat brain consistent with the labelling of all %aL2-adrenoceptor subtypes, namely α2A/D-, α2B and α2C.
4 In rat, in vivo brain dialysis experiments demonstrated peripherally administered RX821002 elevated basal noradrenaline in frontal cortex and also, although to a lesser extent, in ventral hippocampus. RX821002 was also able to elevate extracellular dopamine in the striatum.
5 A 7-day i.c.v. infusion of an antisense oligonucleotide targeting the α2A/D-adrenoceptor, resulted in a significant reduction in the autoradiographic density of [3H]-RX821002 binding in specific brain areas, notably the lateral septal nuclei and anterior hypothalamic area.
6 Several years of research by our group has extended our knowledge of the pharmacology and function of the α2-adrenoceptor and has provided evidence of the roles of this receptor in the control of monoamine turnover. The successful use of antisense technology to knockdown expression of the α2A/D subtype provides future opportunities to explore the physiology of this receptor subtype.