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Naunyn-Schmiedeberg's Archives of Pharmacology

, Volume 338, Issue 5, pp 543–547 | Cite as

Biochemical evidence that brainstem adrenaline-containing neurons are activated during clonidine withdrawal in the spontaneously hypertensive rat

  • Laura Lambás-Señas
  • Jeffrey Atkinson
  • Jean-Pierre Fluckiger
  • Mireille Sonnay
  • Geneviève Chamba
  • Bernard Renaud
Article

Summary

We have investigated the effects of prolonged treatment with clonidine (delivered intravenously via osmotic minipumps, 0.1 mg/kg/day for 7 or 10 days) and of withdrawal of such treatment on brainstem noradrenaline and adrenaline metabolism in the adult spontaneously hypertensive rat (SHR). After a seven day treatment with clonidine, noradrenaline and adrenaline turnovers were unchanged both in the A2-C2 and A1-C1 regions. During withdrawal, the noradrenaline turnover was also unchanged in these regions. However, the adrenaline turnover was significantly increased 16 h after withdrawal (p < 0.01) in the A2-C2 region and 16 h (p < 0.01) and 40 h (p < 0.05) after withdrawal in the A1-C1 region. These results show that noradrenaline metabolism is unchanged both during clonidine treatment and during its withdrawal in the brainstem catecholaminergic regions analyzed. In contrast, the increases in adrenaline turnover found in the A2-C2 and A1-C1 regions suggest that the adrenergic neurons of the brainstem could be activated during clonidine withdrawal. As the adrenergic CI neurons are a key element of the sympathetic vasopressor system, the increase in adrenaline turnover observed during withdrawal could be at the origin of the sympathetic hyperactivity found after cessation of prolonged treatment with clonidine.

Key-words

Adrenaline Clonidine Noradrenaline Turnover Withdrawal 

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Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Laura Lambás-Señas
    • 1
  • Jeffrey Atkinson
    • 2
  • Jean-Pierre Fluckiger
    • 2
  • Mireille Sonnay
    • 2
  • Geneviève Chamba
    • 2
  • Bernard Renaud
    • 1
  1. 1.Laboratoire de Neuropharmacologie-CNRS, Faculté de PharmacieUniversité Claude BernardLyon Cedex 08France
  2. 2.Laboratoire de Pharmacodynamie, Faculté de PharmacieUniversité de Nancy INancyFrance

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