Neurochemical Research

, Volume 10, Issue 8, pp 1143–1154 | Cite as

Changes in the alpha-adrenoceptors in the medulla oblongata including nucleus tractus solitarii of spontaneously hypertensive rats

  • Masahiko Nomura
  • Masataka Ohtsuji
  • Yutaka Nagata
Original Articles

Abstract

The nucleus tractus solitarii (NTS) is a brain stem center mediating depression of blood pressure. In order to elucidate a possible mechanism for the central regulation of blood pressure, we studied noradrenergic indices in the medulla oblongata, a region including the NTS, in spontaneously hypertensive rats (SHR) as compared with normotensive controls of the Wistar Kyoto strain (WKY) at 12 weeks of age. The medulla oblongata was the only brain region showing a significantly low noradrenaline level in the SHR as compared with WKY rats; the level is also significantly decreased at 8 weeks of age. The alpha 1-adrenergic binding sites, as measured with 2-(2′, 6′-dimethoxy) phenoxyethylamine-methylbenzodioxan [3H]WB4101 showed significant increases inKD andBmax values in medulla oblongata homogenates from rats of both strains from 4–12 weeks after birth, with no significant interstrain difference. On the other hand, theKD andBmax of the alpha 2-sites, measured by [3H]yohimbine binding, were reduced in SHR as compared to WKY animals, even at 4 weeks after birth when hypertension was not yet apparent. As expected, the relatively selective alpha 2-antagonist, clonidine, was a potent inhibitor of [3H]yohimbine binding but not of [3H]WB4101 binding in these homogenates. The results suggest that some genetic disorder in the alpha 2-adrenergic transmission system in the NTS region may be involved in the development of hypertension in the SHR rats.

Keywords

Clonidine Medulla Oblongata Nucleus Tractus Solitarii Dimethoxy Interstrain Difference 

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Copyright information

© Plenum Publishing Corporation 1985

Authors and Affiliations

  • Masahiko Nomura
    • 1
  • Masataka Ohtsuji
    • 1
  • Yutaka Nagata
    • 1
  1. 1.Department of Physiology School of MedicineFujita-Gakuen Health UniversityToyoake, AichiJapan

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