Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 279, Issue 3, pp 285–300 | Cite as

Central nervous α-adrenergic receptors and the mode of action of α-methyldopa

  • A. Heise
  • G. Kroneberg
Article

Summary

Experiments in cats with perfusion of the fourth and parts of the third cerebral ventricle gave the following results:
  1. 1.

    Perfusions with α-methyldopa, α-methyldopamine, α-methylnoradrenaline, noradrenaline, or tyramine produced a significant decrease of the systemic arterial blood pressure. A dose-response relationship of this effect was demonstrated with noradrenaline and α-methylnoradrenaline.

     
  2. 2.

    The blood pressure lowering effect of the amines was inhibited or abolished by perfusion with phentolamine or yohimbine.

     
  3. 3.

    The depressor effect of perfusions with tyramine was inhibited after addition of 2μg/ml cocaine to the perfusion fluid. Cocaine perfusion enhanced the depressor effect of α-methylnoradrenaline.

     
  4. 4.

    In the reserpine-pretreated cat the effect of tyramine was strongly inhibited. α-Methylnoradrenaline had no effect under these conditions.

     
  5. 5.

    Perfusions with angiotensin produced an increase of the peripheral blood pressure, while isoprenaline and propranolol showed no significant activity.

     
  6. 6.

    In the intact anaesthetized, as well as in the spinal, cat the intravenous pressor activities of noradrenaline and α-methylnoradrenaline were nearly identical. The response of the isolated aortic strip of the rat was somewhat more pronounced to α-methylnoradrenaline than to noradrenaline.

     
  7. 7.

    The results of these investigations are in favour of the hypothesis that in the brain stem an α-receptor mechanism exists, which is able to mediate a blood pressure decreasing effect of centrally applied catecholamines. The central hypotensive action of α-methyldopa may be explained by this mechanism.

     

Key words

α-Adrenergic Receptors α-Methyldopa Catecholamines Central Activity Central Nervous System Blood Pressure 

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Copyright information

© Springer-Verlag 1973

Authors and Affiliations

  • A. Heise
    • 1
  • G. Kroneberg
    • 1
  1. 1.Institut für PharmakologieBayer AGWuppertalGermany

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