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  • 1
    Electronic Resource
    Electronic Resource
    Similarity between the effects of suprachiasmatic nuclei lesions and of pinealectomy on gonadotropin release in ovariectomized, sulpiride-treated and melatonin-replaced rats (1993)
    Springer
    Cellular and molecular life sciences 49 (1993), S. 797-801 
    Details
    ISSN: 1420-9071
    Keywords: Pinealectomy ; suprachiasmatic nuclei lesions ; ovariectomy ; LH ; FSH ; melatonin ; sulpiride-treated rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The aim of this study was to compare the effects of pineal indole treatments on LH and FSH release in pinealectomized and suprachiasmatic lesioned and ovariectomized rats rendered hyperprolactinemic by acute sulpiride treatment. pinealectomy or suprachiasmatic nuclei lesions in female rats both decreased plasma LH and FHS at 10, but not at 20 d after surgery, whereas the daily afternoon administration of melatonin effectively restored levels of both gonadotropins to control values. In ovariectomized rats, pinealectomy or suprachiasmatic nuclei lesions were ineffective in counteracting the high plasma levels of LH and FSH. However, sulpiride treatment in both pinealectomized and suprachiasmatic nuclei lesioned and castrated female rats significantly decreased the levels of LH and FSH, an effect which was counteracted by daily afternoon melatonin administration. Other pineal indoles tested, i.e., 5-hydroxy- and 5-methoxytryptophol, were ineffective in regulating gonadotropin levels. The results suggest that the pineal gland, through its hormone melatonin, can modulate gonadotropin secretion by acting on a dopamine mechanism independent of hypothalamic suprachiasmatic areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01923552
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  • 2
    Electronic Resource
    Electronic Resource
    Calcium-Dependent Effects of Melatonin Inhibition of Glutamatergic Response in Rat Striatum (2001)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 13 (2001), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of melatonin, amlodipine, diltiazem (l-type Ca2+ channel blockers) and ω-conotoxin (N-type Ca2+ channel blocker) on the glutamate-dependent excitatory response of striatal neurones to sensory-motor cortex stimulation was studied in a total of 111 neurones. Iontophoresis of melatonin produced a significant attenuation of the excitatory response in 85.2% of the neurones with a latency period of 2 min. Iontophoresis of either l- or N-type Ca2+ channel blocker also produced a significant attenuation of the excitatory response in more than 50% of the recorded neurones without significant latency. The simultaneous iontophoresis of melatonin + amlodipine or melatonin + diltiazem did not increase the attenuation produced by melatonin alone. However, the attenuation of the excitatory response was significantly higher after ejecting melatonin + ω-conotoxin than after ejecting melatonin alone. The melatonin–Ca2+ relationship was further supported by iontophoresis of the Ca2+ ionophore A-23187, which suppressed the inhibitory effect of either melatonin or Ca2+ antagonists. In addition, in synaptosomes prepared from rat striatum, melatonin produced a decrease in the Ca2+ influx measured by Fura-2AM fluorescence. Binding experiments with [3H]MK-801 in membrane preparations from rat striatum showed that melatonin did not compete with the MK-801 binding sites themselves although, in the presence of Mg2+, melatonin increased the affinity of MK-801. The results suggest that decreased Ca2+ influx is involved in the inhibitory effects of melatonin on the glutamatergic activity of rat striatum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2001.00656.x
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanisms of N-methyl-d-Aspartate Receptor Inhibition by Melatonin In the Rat Striatum (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 16 (2004), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: N-methyl-d-aspartate (NMDA) receptor activation comprises multiple regulatory sites controlling Ca2+ influx into the cell. NMDA-induced increases in intracellular [Ca+2] lead to nitric oxide (NO) production through activation of neuronal NO synthase (nNOS). Melatonin inhibits either glutamate or NMDA-induced excitation, but the mechanism of this inhibition is unknown. In the present study, the mechanism of melatonin action in the rat striatum was studied using extracellular single unit recording of NMDA-dependent neuronal activity with micro-iontophoresis. Melatonin inhibited neuronal excitation produced by either NMDA or l-arginine. The effects of both NMDA and l-arginine were blocked by nitro-l-arginine methyl ester, suggesting that nNOS participates in responses to NMDA. However, excitation of NMDA-sensitive neurones induced by the NO donor sodium nitroprusside was only slightly modified by melatonin. Melatonin iontophoresis also counteracted excitation induced by tris(2-carboxyethyl)phosphine hydrochloride, showing that the redox site of the NMDA receptor may be a target for melatonin action. The lack of effects of the membrane melatonin receptor ligands luzindole, 4-phenyl-2-propionamidotetralin and 5-methoxycarbonylamino-N-acetyltryptamine, and the nuclear melatonin ligand, CGP 52608, a thiazolidine dione, excluded the participation of known membrane and nuclear receptors for melatonin. The data suggest that inhibition of NMDA-dependent excitation by melatonin involves both nNOS inhibition and redox site modulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.2004.01250.x
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  • 4
    Electronic Resource
    Electronic Resource
    Day-night variations in melatonin secretion by the pineal gland during febrile and epileptic convulsions in children
    Amsterdam : Elsevier
    Psychiatry Research 52 (1994), S. 273-283 
    Details
    ISSN: 0165-1781
    Keywords: Circadian rhythms ; children ; epilepsy ; seizures
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0165-1781(94)90073-6
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  • 5
    Electronic Resource
    Electronic Resource
    Melatonin interaction with magnesium and zinc in the response of the striatum to sensorimotor cortical stimulation in the rat (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 24 (1998), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Eseames G, Acuña-Castroviejo D, León J, Vives F. Melatonin interaction with magnesium and zinc in the response of the striatum to sensorimotor cortical stimulation in the rat. J. Pineal Res. 1998; 24:123–129. © Munksgaard, Copenhagen〈section xml:id="abs1-1"〉〈title type="main"〉AbstractThe sensorimotor cortex (SMCx) sends numerous projections to the striatum. These projections are excitatory and glutamate mediated. Glutamatergic receptors, specifically those of NMDA type-receptors, are closely related to excitotoxicity. Thus, in some circumstances, an excess of Ca2+ influx through NMDA channels alters neuronal metabolism and may become lethal for the cell. Two other divalent cations, Mg2+ and Zn2+, have inhibitory effects on NMDA receptors. Magnesium ions exert a voltage-dependent block of the NMDA calcium channel, whereas zinc ions exert a voltage-independent NMDA block. In the present work, the effects of iontophoresis of Mg2+ and Zn2+ on the striatal response to SMCx stimulation were studied. Moreover melatonin, an indoleamine with anticonvulsant properties and inhibitory effects on the NMDA receptor, was also iontophorized alone or in combination with Mg2+ and Zn2+. Single pulse electrical stimulation of SMCx produced an excitatory response in the striatum. Iontophoresis of melatonin, Mg2+ and Zn2+ produced a potent attenuation of the excitatory response of the striatum to SMCx stimulation, although the latency of the effect of melatonin was longer than those of Mg2+ and Zn2+. When these cations were simultaneously ejected with melatonin, additive inhibitory effects were recorded. These observations suggest that the inhibitory effects produced by Mg2+ and Zn2+ and melatonin are produced via different processes, and thus the inhibitory role of melatonin on the NMDA receptor activity is exclusive of a direct action on the NMDA calcium channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1998.tb00377.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of clonidine on plasma ACTH, cortisol and melatonin in children (2000)
    Copenhagen : Munksgaard
    Journal of pineal research 29 (2000), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 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 α2-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 α2-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 α2-adrenoceptor agonist clonidine (100 μg/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 α2-adrenergic influence on both the pineal gland and the hypothalamus-pituitary-adrenal in children and further support the presence of α2-adrenoceptors in the human pineal gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-079X.2000.290107.x
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  • 7
    Electronic Resource
    Electronic Resource
    Melatonin-induced increased activity of the respiratory chain complexes I and IV can prevent mitochondrial damage induced by ruthenium red in vivo (2000)
    Copenhagen : Munksgaard
    Journal of pineal research 28 (2000), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Melatonin displays antioxidant and free radical scavenger properties. Due to its ability with which it enters cells, these protective effects are manifested in all subcellular compartments. Recent studies suggest a role for melatonin in mitochondrial metabolism. To study the effects of melatonin on this organelle we used ruthenium red to induce mitochondrial damage and oxidative stress. The results show that melatonin (10 mg/kg i.p.) can increase the activity of the mitochondrial respiratory complexes I and IV after its administration in vivo in a time-dependent manner; these changes correlate well with the half-life of the indole in plasma. Melatonin administration also prevented the decrease in the activity of complexes I and IV due to ruthenium red (60 μg/kg i.p.) administration. At this dose, ruthenium red did not induce lipid peroxidation but it significantly reduced the activity of the antioxidative enzyme glutathione peroxidase, an effect also counteracted by melatonin. These results suggest that melatonin modulates mitochondrial respiratory activity, an effect that may account for some of the protective properties of the indoleamine. The mitochondria-modulating role of melatonin may be of physiological significance since it seems that the indoleamine is concentrated into normal mitochondria. The data also support a pharmacological use of melatonin in drug-induced mitochondrial damage in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-079X.2000.280407.x
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of propranolol plus exercise on melatonin and growth hormone levels in children with growth delay (2001)
    Copenhagen : Munksgaard International Publishers
    Journal of pineal research 30 (2001), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The pineal gland in humans is under both α- and β-adrenergic control, although it seems that β1-adrenoceptors are mainly implicated in melatonin secretion. In the present study, we evaluated the role of β-adrenergic innervation on melatonin production and its relation with the production of growth hormone (GH). Thirty-four children (15 males and 19 females, mean age 10.5±0.8 years) from the University of Granada Hospital were studied. The children were included in a protocol for the evaluation of growth delay using the propranolol+exercise test. This standardized test allowed us to study simultaneously the role of an unspecific β-adrenergic blocker such as propranolol and of an adrenergic stimulus such as exercise on the pineal production of melatonin. Changes in plasma levels of melatonin and GH were determined at basal, 120 and 140 min after the test was applied. Hormonal determinations were carried out by commercial radioimmunoassay kits previously standardized in our laboratory. The results show a significant decrease in plasma melatonin levels at 120 and 140 min after the test (P〈0.05), whereas GH levels increased significantly at 140 min (P〈0.001). The decrease of melatonin levels was a consequence of the test, since in a control group, the circadian decay of melatonin was significantly less pronounced (P〈0.05). These data suggest an inverse relationship between melatonin and GH after the propranolol+exercise test, and the reduction in melatonin may be related to its depletion by exercise-induced oxidative stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-079X.2001.300202.x
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  • 9
    Electronic Resource
    Electronic Resource
    Comparative effects of melatonin, l-deprenyl, Trolox and ascorbate in the suppression of hydroxyl radical formation during dopamine autoxidation in vitro (2000)
    Copenhagen : Munksgaard
    Journal of pineal research 29 (2000), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Degeneration of nigrostriatal dopaminergic neurons is the major pathogenic substrate of Parkinson's disease (PD). Inhibitors of monoamine oxidase B (MAO-B) have been used in the treatment of PD and at least one of them, i.e., deprenyl, also displays antioxidant activity. Dopamine (DA) autoxidation produces reactive oxygen species implicated in the loss of dopaminergic neurons in the nigrostriatal pathway. In this study we compared the effects of melatonin with those of deprenyl and vitamins E and C in preventing the hydroxyl radical (•OH) generation during DA oxidation. The rate of production of 2,3-dihydroxybenzoate (2,3-DHBA) in the presence of salicylate, an •OH scavenger, was used to detect the in vitro generation of •OH during iron-catalyzed oxidation of DA. The results showed a dose-dependent effect of melatonin, deprenyl and vitamin E in counteracting DA autoxidation, whereas vitamin C had no effect. Comparative analyses between the effect of these antioxidants showed that the protective effect of melatonin against DA autoxidation was significantly higher than that of the other compounds tested. Also, when melatonin plus deprenyl were added to the incubation medium, a potentiation of the antioxidant effect was found. These findings suggest that antioxidants may be useful in brain protection against toxicity of reactive oxygen species produced during DA oxidation, and melatonin, alone or in combination with deprenyl, may be an important component of the brain's antioxidant defenses to protect it from dopaminergic neurodegeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-079X.2000.290206.x
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  • 10
    Electronic Resource
    Electronic Resource
    5-Methoxytryptophol and melatonin in children: Differences due to age and sex (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 21 (1996), S. 0 
    Details
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: It seems clear that the pineal hormone, melatonin (N-acetyl-5-methoxytryptamine), is involved in the reproductive behavior of several animal species including humans. Moreover, several data also support a role for 5-methoxytryptophol (ML), another pineal hormone, in the control of sexual processes. To test the role of ML in human reproductive axis, 128 healthy children, 68 boys and 60 girls, were studied. Each of these groups was divided in three age subgroups of 6, 11, and 14 years. A single blood sample (0900 hours) was obtained from each subject to determine melatonin, ML, FSH, LH, estradiol (girls), and testoterone (boys) by RIA. Statistical analysis of the data included ANOVA-II (factor I: age, factor II: sex) and an analysis of covariance with age as covariate. A similar plasma melatonin concentration, with a significant decrease between 6 and 11 years, was found in boys and girls. Melatonin concentrations correlate well with initiation of the pubertal development in these children, although no sex differences were found. Concentrations of ML are approximately 50% of those of melatonin. In contrast to melatonin, ML levels show significant age and sex differences. Plasma ML concentration significantly increased in boys (P 〈 0.001) and decreased in girls (P 〈 0.001) after 8 years of age. These results support the hypothesis that, besides melatonin, other pineal compounds such as ML may be involved in the maturation process in humans. The pineal indole ML may also be used as a marker of the different chronobiology in the pubertal development in boys and girls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-079X.1996.tb00273.x
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