The effect of clonidine and bright light on plasma melatonin

Grasby, Paul M.; Cowen, Philip J.

doi:10.1002/hup.470030107

Cited by 5 publications

(1 citation statement)

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“…Lewy et al [1986] reported a dose-dependent reduction in plasma melatonin concentration following clonidine administration to normal subjects. Grasby and Cowen [1988] using a smaller dose of clonidine, failed to replicate this finding, suggesting that changes in melatonin secretion may be strongly dependent on the a 2 -agonist dose. Anyway, changes in diurnal melatonin levels induced by clonidine are difficult to detect due to the low levels of the hormone during the morning and its normal circadian decay.…”

Section: Discussionmentioning

confidence: 96%

Effect of clonidine on plasma ACTH, cortisol and melatonin in children

Muñóz-Hoyos

Fernández-García

Molina-Carballo

et al. 2000

Journal of Pineal Research

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An interaction between melatonin and adrenocorticotropin (ACTH) seems to occur in humans and both hormones respond to beta-adrenergic stimulation. As in lower animal species, human pineal gland also contains alpha2-adrenergic receptors as does the hypothalamus-pituitary axis. In this study the response of the pineal gland and of the hypothalamus-pituitary-adrenal axis to alpha2-adrenergic stimulation was assessed. Twenty-nine children (21 males, mean age 11.2 +/- 0.6 yr and eight females, mean age 9.1 +/- 1.1 yr) from the University of Granada Hospital were studied. The children were diagnosed as having growth problems but with a normal response of growth hormone (GH) to clonidine test. Changes in plasma levels of ACTH, cortisol and melatonin were evaluated in these children after oral administration of the alpha2-adrenoceptor agonist clonidine (100 microg/m2) or a placebo. Plasma ACTH, cortisol and melatonin were measured before (basal) and at 30, 60 and 90 min after oral clonidine or placebo administration. Hormonal determinations were carried out by commercial radioimmunoassay kits, previously standardised in our laboratory. The results show a significant decrease in plasma ACTH, cortisol and melatonin 30 min after clonidine administration (P < 0.001), reaching lowest values at 90 min after the drug was administered. The reduction in the levels of these hormones is independent of their normal circadian decay since the control group showed a significantly different pattern of behaviour. These data support the existence of an inhibitory alpha2-adrenergic influence on both the pineal gland and the hypothalamus-pituitary-adrenal in children and further support the presence of alpha2-adrenoceptors in the human pineal gland.

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Section: Discussionmentioning

confidence: 96%