Loss of the effects of (Ionidine on the growth hormone release and hypotensive action in long-term castrated rats: The possible role of testosterone on alpha-2-adrenergic mechanisms of clonidine

Do Thanh Kiem, Ervin Stark, Mårton I.K. Fekete

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The effect of testosterone on the growth hormone (GH)-releasing and hypotensive actions of clonidine was evaluated in vivo using male Wistar rats. Clonidine at various doses and by various routes (5 µg/kg, i.c.v.; 15 µg/kg, i.v., and 7, 15, 31, 125 and 250 µg/kg, i.v.) induced a significant increase in plasma GH levels in rats. Intracerebroventricular (5 µg/kg) injection of clonidine significantly decreased blood pressure. The effects of clonidine on the GH release and blood pressure were lost in long-term castrated rats, but were restored by testosterone replacement in the castrates. In addition, the hypotensive response to clonidine in testosterone-replaced castrated rats lasted longer than in the sham-operated rats. The injection of yohimbine (3 mg/kg, i.p.) strongly inhibited the secretion of GH induced by clonidine treatment in sham-operated animals, and its inhibitory action was significantly attenuated in castrates. In long-term castrated rats, basal blood pressure decreased significantly compared with that of sham-operated rats. This was also restored after testosterone administration to castrates. The results of the present study indicate that the α2-adrenergic receptor-mediated effects of clonidine on the GH release and blood pressure might be dependent on the endogenous testosterone secretion.

Original languageEnglish
Pages (from-to)226-232
Number of pages7
JournalNeuroendocrinology
Volume51
Issue number2
DOIs
Publication statusPublished - Jan 1 1990

Keywords

  • Clonidine
  • GH release
  • Hypotensive action
  • Testosterone
  • α<inf>2</inf>-Adrenoreceptor

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology
  • Endocrine and Autonomic Systems
  • Cellular and Molecular Neuroscience

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