Effects of Methyldopa Metabolites on Amine Transmitters and Adrenergic Receptors in Rat Brain

William J. Louis, Elizabeth Conway, Roger Summers, Philip Beart, Bevyn Jarrott

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Abstract

Studies of catecholamine concentrations in defined nuclei from the anterior hypothalamic-preoptic regions and the medulla oblongata, known to contribute to cardiovascular control, were measured following acute or chronic methyldopa administration. These studies indicated that methyldopa was enzymatic-ally converted to methyldopamine and methylnorepinephrine, and in some areas to methylepinephrine which replaced endogenous epinephrine. The predominant metabolite was methylnorepinephrine, which accumulated in concentrations higher than endogenous norepinephrine levels. (-)Methylnorepinephrine was found to be 6 times more potent and 75 times more selective for α2-adrenergic receptors than (-) norepinephrine, and it is suggested that this α2-adrenergic receptor action, particularly in the nucleus tractus solitarius, contributes to a major part of the antihypertensive effect of methyldopa.

Original languageEnglish
Pages (from-to)40-44
Number of pages5
JournalHypertension
Volume6
Issue number5
Publication statusPublished - 1 Jan 1984

Keywords

  • Methyldopa
  • Radioligand receptor assays
  • Rat brain
  • α-methyldopamine
  • α-methylnorepinephrine
  • α<inf>2</inf>-adrenergic receptors

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