A single corticosterone pretreatment inhibits the hypothalamic-pituitary-adrenal responses to adrenergic and cholinergic stimulation

The purpose of the present study was to determine whether an increased plasma corticosterone or dexamethasone levels induced by a single corticosterone or dexamethasone injection to conscious rats affects the hypothalamic-pituitary-adrenocortical (HPA) activity induced by adrenergic and cholinergic...

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Published in:Journal of physiology and pharmacology : an official journal of the Polish Physiological Society 2001-06, Vol.52 (2), p.313-324
Main Authors: Bugajski, J, Gadek-Michalska, A, Bugajski, A J
Format: Article
Language:English
Subjects:
Adrenergic Agonists - pharmacology
Adrenocorticotropic Hormone - blood
Animals
Anti-Inflammatory Agents - pharmacology
Cholinergic Agonists - pharmacology
Corticosterone - blood
Corticosterone - pharmacology
Hypothalamo-Hypophyseal System - drug effects
Hypothalamo-Hypophyseal System - metabolism
Male
Pituitary-Adrenal System - drug effects
Pituitary-Adrenal System - metabolism
Rats
Rats, Wistar
Receptors, Adrenergic - metabolism
Receptors, Cholinergic - metabolism
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Summary:The purpose of the present study was to determine whether an increased plasma corticosterone or dexamethasone levels induced by a single corticosterone or dexamethasone injection to conscious rats affects the hypothalamic-pituitary-adrenocortical (HPA) activity induced by adrenergic and cholinergic agonists. Male Wistar rats were pretreated subcutaneously (s.c.) with a single dose of dexamethasone (5 mg/kg) or corticosterone (25 mg/kg) 24 or 48 h before intraperitoneal (i.p.) administration of adrenergic agonists: phenylephrine, an alpha1-adrenergic receptor agonist, clenbuterol, a beta2-adrenergic agonist and noradrenaline acting predominantly on alpha1-adrenoreceptors, and cholinergic agonists: carbachol, a predominant muscarinic receptor agonist and nicotine, a nicotinic receptor agonist. Dexamethasone profoundly decreased the resting ACTH levels in control rats and given 24 h before each of the stimulatory agonist abolished the adrenergic- and cholinergic agonists-induced ACTH and corticosterone responses. Pretreatment with corticosterone of control rats did not substantially alter the resting plasma ACTH and serum corticosterone levels measured 24 and 48 h later. A single pretreatment with corticosterone abolished or powerfully inhibited, perhaps by a feedback mechanism, the ACTH and corticosterone responses induced 24 and 48 h later by all adrenergic and cholinergic agonists used in this study. These results indicate that prolonged administration of corticosterone is not necessary to induce almost complete suppression of the HPA responsiveness to adrenergic or cholinergic stimulation. Chronic treatment with corticosteroids to achieve glucocorticoid receptors desensitization does not seem to be required.
ISSN:0867-5910