In order to assess the existence of a rhythmic secretion of melatonin (aMT) in newborns and whether this rhythm is affected by neonatal stress, we studied 112 newborns classified in three groups: normal babies delivered at term, preterm infants born before the 38th week, and babies with fetal distress. Melatonin was measured by RIA in the umbilical artery and vein at the time of birth. Melatonin levels in umbilical arterial and venous blood showed a diurnal rhythm in all groups. Melatonin levels in umbilical cord artery and vein were closely related. Nocturnal melatonin levels were increased in newborns with acute fetal distress in comparison with normal term and preterm neonates. These results suggest that (1) a rhythm of aMT secretion exists in newborns, although it cannot be determined whether this rhythm is of maternal or fetal origin and (2) neonatal stress (acute fetal distress) increases aMT production during the night in comparison with normal term and preterm neonates.

Our results point to the existence of an imbalance in the tryptophan metabolite pathways during convulsions, blunting the normal diurnal-nocturnal rhythm of kynurenines. They also support the idea of a difference in the production of tryptophan metabolites between febrile and epileptic patients, suggesting that the tryptophan pathways follow different routes depending upon the type and duration of the convulsion.

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.

Background: Specific immunotherapy for respiratory allergy, a seasonal disease, significantly reduces the inflammatory process, attenuating the clinical symptoms. The mechanism for the clinical beneficial effect of immunotherapy has not yet been clarified. Melatonin shows a circadian and seasonal variation and together with the endogenous opioid system plays an immunomodulatory role acting on both specific and nonspecific immunity responses. Thus, the possibility that immunotherapy involved changes in the melatonin-opioid system was investigated. Methods: Thirty-five children aged 3–15 years with rhinitis and asthma due to olive + grass pollen sensitization were studied. The patients were treated with depot extracts containing the identified allergens with increasing doses from 1 to 1,000 IU/ml during 3 months. Melatonin, β-endorphin, total and specific IgE and IgG4 were determined before and after treatment. Results: All children showed a significant improvement of their symptoms at the end of the treatment, coinciding with a significant drop of both melatonin and β-endorphin levels. Total IgE decreased in most of the cases although the mean values did not show significant changes. Specific IgE and IgG4 were also unchanged. A significant correlation between melatonin and β-endorphin and between β-endorphin and IgG4 was found before immunotherapy, and these correlations disappeared when the treatment was finished. Conclusions: The decrease in the levels of melatonin and β-endorphin suggests the disappearance of their stimulating influence on the immune system. Thus, hyposensitization after immunotherapy may involve, at least in part, the inhibition of the immunoenhancing properties of the melatonin-opioid system.

Aims-To investigate whether the lipid profile of pregnant women during parturition differs from the profile at previous stages of pregnancy and to determine the effects of maternal lipid changes on fetal or neonatal haemorheology. Methods-Sixty pregnant women were studied, divided into two groups. Group 1 contained 30 women ofmean age of27 (SD 3) years and gestational age >38 weeks in whom delivery had not yet begun; all these pregnancies followed an uncomplicated course and there was no evidence of any fetal pathology from previous obstetric examinations. All the women reached term and birth weight was 3340 (350) (J7 Clin Pathol 1996;49:120-123)