bluuebunny/crossref_metadata_2025 huggingface dataset:
The clinical neuroimmunotherapeutic role of melatonin in oncology
Authors: Conti Ario , Maestroni Georges J.M.
Published: February 2007

Abstract: In the past several years, interest in the immunophysiological role of the pineal gland and melatonin has grown to the extent that now their immunoregulatory role is widely recognized. Melatonin has immunoenhancing properties and it is able to counteract the immunodepression induced by acute stress, drug treatment (i.e., anticancer drugs), and viral infections. Here we review the therapeutic efficacy of melatonin alone or in combination with interleukin‐2 (IL‐2) in cancer patients who did not respond to standard anticancer chemotherapies and/or refused any aggressive treatment. In this review, we summarize a series of reports from 1986 through 1994 in which patients affected by metastatic solid tumors, metastatic non‐small‐cell lung cancer, advanced solid neoplasms, myelodysplastic syndrome, hepatocellular carcinoma, and advanced endocrine tumors were studied. The conclusion drawn from these studies is that melatonin protects against IL‐2 and synergizes with the IL‐2 anticancer action. This combined strategy represents a well tolerated intervention to control tumor growth. In most cases performance status and quality of life seem improved.
Nocturnal plasma melatonin levels in patients suffering from chronic primary insomnia
Authors: Hajak Göran , Rodenbeck Andrea , Staedt Jürgen , Bandelow Borwin , Huether Gerald , Rüther Eckart
Published: February 2007

Abstract: Polysomnographic sleep patterns and melatonin secretion were investigated in 10 patients (age: 41.3 ± 9.5 years) who suffered from chronic primary insomnia and complained predominantly about difficulties in maintaining sleep and in five healthy controls (age 27.2 ± 0.7 years). Nocturnal plasma melatonin concentrations were obtained hourly, measured by direct radioimmunoassay and statistically compared between insomniacs and controls with age as a covariate. Plasma melatonin levels in the patient group tended to begin increasing earlier in the evening and were significantly (P ± 0.01) lower during the middle of the night (peak value 82.5 ± 26.5 pg/ml) than in the healthy controls (peak value 116.8 ± 13.5 pg/ml). Among the patients, the most severely reduced nocturnal plasma melatonin levels were found in those patients with a history of sleep disturbance lasting for longer than five years (N = 6; age 41.8 ± 11.7 years; duration 15.3 ± 5.9 years; peak value 72.1 ± 25.0 pg/ml); whereas those chronic insomniacs affected for fewer than five years had relatively higher nocturnal levels (N = 4; age 40.6 ± 6.5 years; duration 3.8 ± 1.5 years; peak value 98.2 ± 23.9 pg/ml). These results show that the circadian rhythm of melatonin secretion is disturbed in patients with chronic primary insomnia, and that the nocturnal plasma melatonin secretion is increasingly more affected the longer the patients are unable to maintain a regular sleep pattern.
Pharmacologic studies on the mechanism of melatonin‐induced vasorelaxation in rat aorta
Authors: Weekley L. Bruce
Published: February 2007

Abstract: The influence of several classes of drugs on the melatonin‐induced vasorelaxation of isolated rat aorta were examined. Melatonin caused a dose‐dependent relaxation of precontracted (30 mM KC1) aorta. This relaxant response was blocked by preincubating vessels with antagonists of vasoactive intestinal peptide. Substance P antagonists did not alter the response to melatonin. Pretreatment of vessels with 6‐hydroxydopamine, lidocaine, or tetrodotoxin antagonized the relaxant response to melatonin. On the other hand, pretreatment with atropine + propranolol did not alter the response to melatonin. These experiments suggest that melatonin may exert part of its vasoactive actions by an interaction with perivascular nerve terminals.
Thirty years of human pineal research: Do we know its clinical relevance?
Authors: Garcia‐Patterson Apolonia , Puig‐Domingo Manuel , Webb Susan M.
Published: February 2007

Abstract: A role for melatonin in humans is becoming evident in an increasing number of clinical situations. Marked variations in the magnitude of the nocturnal melatonin peak are observed throughout the human lifespan. The highest levels occur in children and then fall during puberty and further during adulthood. A negative correlation between circulating melatonin and sex steroids has been observed in a number of instances, and appears to be independent of concomitant gonadotrophins. No clear melatonin pattern has been observed in pituitary tumors, but in large lesions that involve the hypothalamus, a reduced nocturnal rise has been reported. Reported effects of exogenously administered melatonin are variable, probably reflecting differences in dose and timing; a slight stimulation of prolactin, as well as a partial inhibition of gonadotrophins, has been reported, which explains its utility as an oral contraceptive, associated with a progestogen. A potential clinical use of melatonin as an oncostatic drug still awaits confirmation, although experimental data firmly support this possibility. The indole has also been used to hasten entrainment of subjects travelling across various time zones, and has been found to be specially useful in eastward travel. Finally, changes in the normal melatonin circadian pattern have been reported in psychiatric diseases and in sudden infant death syndrome.
Specific binding of 2‐[125I]iodomelatonin by rat spleen crude membranes: Day‐night variations and effect of pinealectomy and continuous light exposure
Authors: Rafii‐EI‐ldrissi Mohammed , Calvo Juan R. , Giordano Mirta , Guerrero Juan M.
Published: February 2007

Abstract: Melatonin binding sites were characterized in rat spleen crude membranes. The specific binding of 2‐[125I]iodomelatonin by spleen crude membranes fulfills all the criteria for binding to a receptor site. Thus, binding was dependent on time and temperature, stable, specific, and increased under constant light exposure and after pinealectomy. In competition studies, the specific binding of 2‐[125I]iodomelatonin to spleen crude membranes was inhibited by increasing concentrations of native melatonin. Scatchard analysis showed that the data were compatible with the existence of two classes of binding sites: a high affinity site with a Kd of 0.53 nM and a binding capacity of 2.52 pM, and a low‐affinity site with a Kd of 374 nM and binding capacity of 820 pM. Moreover, binding of 2‐[l25I]iodomelatonin exhibited day‐night variations with the highest binding observed late during the light period, and the lowest binding was observed late at night. However, binding of 2‐[125I]iodomelatonin to membranes remained high when animals were kept under light exposure at night. Results support the hypothesis of a regulatory role of melatonin on the immune system in which melatonin downregulates its own binding site.
Nocturnal melatonin and luteinizing hormone rhythms in women with hyperprolactinemic amenorrhea
Authors: Luboshitzky Rafael , Lavi Shahar , Thuma Isaama , Lavie Peretz
Published: February 2007

Abstract: To examine the role of melatonin in pathological hyperprolactinemia we compared untreated young females (N = 5) with hyperprolactinemic amenorrhea owing to pituitary microadenoma to healthy female controls (N = 6). Serum samples for melatonin, prolactin, and luteinizing hormone (LH) concentrations were obtained every 15 min from 1900 hr to 0700 hr in a controlled light‐dark environment with simultaneous sleep recordings. The mean (±SD) light‐time period, dark‐time period, and the integrated nocturnal melatonin secretion values (area under the curve, or AUC) in patients (51 ± 11 pmol/L, 157 ± 33 pmol/L, and 102 ± 19 pmol/min‐L × 103, respectively) were similar to the values obtained in controls (79 ± 39, 165 ± 44, 111 ± 31, respectively). The onset of the nocturnal melatonin rise, peak level, and peak time were similar in the two groups. A significant nocturnal prolactin rise was observed in patients (112 ± 9 vs. 65 ± 11 μg/L, P < 0.006) and controls (19 ± 2 vs. 10 ± 3 μg/L, P < 0.006). The time of prolactin peak was similar in patients and controls (0424 ± 3: 36 vs. 0350 ± 2: 21) and paralleled that of melatonin (0354 ± 1: 46 vs. 0337 ± 1: 30). The mean ± SD light‐time period, dark‐time period, and the AUC values of LH were similar in patients and controls. The number of LH pulses in patients (7.2 ±1.9 per 12 hr) were not different from those in controls (7.7 ±2.1). The LH pulse interval was 100 ± 22 min in patients compared with 94 ± 23 min in controls. The mean (±SD) nocturnal estradiol (E2) levels were significantly lower in patients (84 ±15 pmol/L) than in controls (224 ± 77) (P < 0.005). Analysis of LH and melatonin secretory profiles revealed significant pulses for both hormones. No significant relationship was observed between the LH and melatonin pulses. However, a negative correlation between LH pulse amplitude and the number of melatonin pulses (P < 0.04) and a positive correlation between LH amplitude and duration of melatonin pulses (P < 0.04) were observed. Taken together, these data suggest that the suppression of normal ovarian cycles in women with hyperprolactinemic amenorrhea owing to pituitary microadenoma may be mediated by blocking of gonadotropin action by prolactin at the ovarian level; yet it remains possible that chronically elevated prolactin might prevent the LH surge and thus lead to amenorrhea. Pulsatile melatonin secretion is unaltered in these patients, and the frequent occurrence of amenorrhea in this population is not mediated by melatonin.
Scientific research on the pineal gland and melatonin: A bibliometric study for the period 1966–1994
Authors: López‐Muñoz Francisco , Boya Jesús , Marín Fernando , Calvo Jose Luis
Published: February 2007

Abstract: By means of teledischarge techniques from the database MEDLINE we selected those documents that contained in their title one or several of the following descriptors: pineal*, epiphys* or melatonin*, in addition to the descriptor pineal‐body in the MESH (Medical Subject Headings) section. A total of 7,617 original documents published between 1966 and 1994 were extracted that dealt with any aspect related with the pineal gland or its main secretary product, melatonin. The main bibliometric laws were applied: Price's Law on the increase in scientific literature, Bradford's Law on the dispersion of the scientific literature, and Lotka's Law on the author's productivity. Furthermore, we have analyzed the participation index (PaI) of the main countries within the global production, the productivity index of the authors (PI), and the number of authors/paper index. Our results demonstrate an exponential increase of the scientific literature on the pineal gland (“r” value = 0.983, in contrast with a “r” value = 0.966 after the linear adjustment). The number of publications on melatonin was less than those on other aspects of pineal research until 1991, when this situation was reversed. The journal with the largest number of original papers is Journal of Pineal Research (1st Bradford's zone) with 533 articles, followed by Journal of Neural Transmision (258) and Neuroendocrinology (221), which constituted the 2nd Bradford's zone. The total number of authors is 9,140, responsible for 23,524 authorships. 3.8% of the authors present a PI>1 (large producers), and 64.9% a PI=0 (occasional authors). Lotka's Law was widely fulfilled in this material since 10.3% of the authors are responsible of 50.2% of all the papers. The average number of authors per paper has changed from 2.29 in 1966 to 3.85 in 1994. The most productive country (during the interval between 1988–1994) was USA (PaI = 30.6), followed by Japan (7.15), United Kingdom (6.45), Germany (6.37), France (6.26), Italy (6.15) and Spain (5.34). Of the total number articles published, 86.9% are in English.
Regional differences in the pineal gland of the cotton rat, Sigmodon hispidus: Light microscopic, electron microscopic, and immunohistochemical observations
Authors: Sakai Yuko , Hira Yoshiki , Matsushima Shoji
Published: February 2007

Abstract: Light microscopic, electron microscopic and immunohistochemical observations of the various portions of the pineal gland of the cotton rat (Sigmodon hispidus) were made. The volume of the proximal half occupied about 30% of the whole organ, and pinealocytes were slightly smaller in size in the proximal portion than elsewhere. The distal and intermediate portions contained few interstitial cells and numerous astrocytes, but the proximal portion lacked interstitial cells and had more abundant astrocytes than elsewhere. Astrocytes, which were immunoreactive for glial fibrillary acidic protein, mainly lined the pericapillary spaces in the distal and intermediate portions, but in the proximal portion these cells often surrounded isolated or groups of pinealocytes. In the distal and intermediate portions, abundant sympathetic fibers and less numerous non‐sympathetic, peptidergic fibers were mainly localized in the pericapillary spaces; these fibers were sparsely distributed in the parenchyma close to interstitial cells or astrocytes. In the proximal portion, non‐sympathetic fibers were scarce and sympathetic fibers were distributed abundantly and almost exclusively in the parenchyma. Most of the sympathetic fibers were adjacent to astrocytes and, occasionally, made specialized contact with them. Fenestrae in the capillary endothelium were numerous in the distal portion but absent in the proximal portion. Thus, marked differences in structure existed between the distal and proximal portions of the pineal gland of the cotton rat, suggesting that both portions are functionally dissimilar. In addition, the present study indicates that the proximal portion of the cotton rat was well developed and showed morphological features similar to the deeply situated pineal glands of other mammals.
HPLC validation of a circadian melatonin rhythm in the pineal gland of inbred mice
Authors: Conti Ario , Maestroni Georges J.M.
Published: February 2007

Abstract: Production of melatonin in the pineal gland of inbred mice such as C57B1/6J, B ALB/c and AKR strains is still a matter of debate. In previous studies, we and other authors showed that these strains of inbred mice have a clear‐cut circadian rhythm of serum melatonin and urinary 6‐hydroxy‐melatonin‐sulphate. In contrast, other groups claimed these mice are unable to synthesize melatonin. These studies were based on RIA measurements and/or estimates of N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) activities. In the present study we validate the presence of melatonin in the pineal gland of C57B1/6, BALB/c, and AKR mice by HPLC determinations. We found a short‐term melatonin peak in the middle of the dark period with a pattern which mirrors that found previously in the serum. The possibility remains, although it seems unlikely, that the pineal melatonin rhythm measured here represents melatonin produced elsewhere which then was subsequently taken up by the pineal gland.
Localization of NADPH‐diaphorase in the rat pineal gland: An experimental enzyme histochemical study
Authors: López‐Figueroa Manuel Oscar , Mailer Morten
Published: February 2007

Abstract: We have used the NADPH‐diaphorase enzyme histochemical technique to localize the enzyme nitric oxide synthase in the rat pineal gland. Some scattered NADPH‐diaphorase positive pineal cells were present, mostly in the rostral part of the gland close to the pineal stalk. In addition, NADPH‐diaphorase positive nerve fibers were located in the pineal capsule, in the connective tissue septae of the gland, and also intraparenchymally between the pinealocytes. Most nerve fibers were endowed with boutons en passage. These nerve fibers remained in the gland after bilateral removal of the superior cervical ganglia verifying a non‐sympathetic nature of the NADPH‐diaphorase positive nerve fibers. Pineal blood vessels also exhibited NADPH‐diaphorase activity. The number and distribution of NADPH‐diaphorase containing cells and nerve fibers were not affected by bilateral superior cervical ganglionectomy. Furthermore, animals sacrificed during day or night exhibited the same NADPH‐diaphorase pattern. The present investigation provides the first morphological evidence for the presence of NADPH‐diaphorase activity in rat pineal cells, suggesting an influence of nitric oxide on pineal metabolism. Furthermore, the presence of NADPH‐diaphorase activity in the pineal blood vessels as well as in the perivascular nerve fibers suggests an influence of nitric oxide on the blood flow to the gland and/or the metabolism of the pineal cells adjacent to the blood vessels.
High repeatability of the amplitude and duration of the nycthemeral rhythm of the plasma melatonin concentration in the Ile‐de‐France ewe
Authors: Chemineau Philippe , Beltran de Heredia Ignacia , Daveau Agnes , Bodin Loys
Published: February 2007

Abstract: In order to determine individual variability in the amplitude and duration of the nycthemeral rhythm of the plasma melatonin concentration, 12 ovariectomized estradiol‐treated Ile‐de‐France ewes were submitted to a sequence of 34 long days (LD1, 16L: 8D), 21 short days (SD, 8L: 16D), and 21 LD (LD2). Intensive blood sampling (hourly from 1 hr before dusk to 1 hr after dawn) was performed for 4 consecutive nights in each of the photoperiodic situations (LD1, SD, LD2), i.e., a total of 12 nights per ewe. Plasma melatonin was assayed by radioimmunoassay. Instantaneous amplitude (difference between each hourly measurement of the plasma melatonin concentration during the nocturnal elevation and the mean diurnal melatonin concentration), mean individual amplitude (same definition but using the mean melatonin concentration during the nocturnal elevation) and duration of elevation of plasma melatonin concentrations were calculated for each ewe and each night and analyzed by variance analysis. Instantaneous amplitude varied significantly with photoperiod, with night intra‐photoperiod, with ewes, and time intra‐night. Mean individual amplitude varied significantly with photoperiod and with ewe but not with night intra‐photoperiod. Dramatic differences between individuals appeared in the amplitude and duration of melatonin rhythms. The lowest mean individual amplitude (all nights of measurement) found was 95 pg/ml and the highest was 544 pg/ml. Overall repeatability coefficient of the mean amplitude of melatonin elevation was 0.71 (P < 0.001). Duration of melatonin elevation varied significantly with photoperiod, with nights intra‐photoperiod and with ewes. During LD periods, mean duration of melatonin elevation was equivalent to duration of the night (from 7 to 8 hr), while during SD it varied with ewes from 9 to 16 hr. Repeatability coefficient of the duration of melatonin elevation in SD was 0.57 (P < 0.05). It is concluded that amplitude and duration (in SD) of the nycthemeral rhythm of the plasma melatonin concentration are highly repeatable individual characteristics in the ewe.
Intracellular calcium release mediated by noradrenaline and acetylcholine in mammalian pineal cells
Authors: Marin Antonio , Urena Juan , Tabares Lucia
Published: February 2007

Abstract: The effects of noradrenergic and cholinergic receptor agonists on intracellular Ca2+ concentration ([Ca2+]i) in single dissociated rat pineal cells were investigated by microfluorimetric measurements in Fura‐2 acetoxymethyl ester (Fura‐2/AM) loaded cells. Noradrenaline (NA) evoked characteristic biphasic increments of intracellular Ca2+ consisting of one or more leading spikes followed by a plateau, resulting from the release of Ca2+ from intracellular stores and from the influx of Ca2+ from the external medium, respectively. This response was reproduced by the α1 adrenoceptor agonist, phenylephrine (PE), in the presence of the β‐adrenoceptor antagonist, propranolol, and was abolished when NA or PE was applied in conjunction with the α1‐adrenoceptor antagonist, prazosin. The curve relating the peak amplitude of the Ca2+ increments to different PE concentrations (0.5–10 μM) showed a half‐maximum response at 0.6 μM PE, and saturation at concentrations greater than 2 μM. Acetylcholine (ACh) also elicited transient Ca2+ increments consisting of an abrupt rise to a maximum value which decayed exponentially to the basal Ca2+ level. A half‐maximum response was achieved at 59 μM ACh. The muscarinic cholinergic receptor agonist, carbachol (CCh), similarly activated Ca2+ increments while the muscarinic antagonist, atropine, abolished them. In the absence of extracellular Ca2+, repetitive stimuli with either α1‐adrenergic and muscarinic agonists produced a progressive decrement in the amplitude of the Ca2+ signals because of the depletion of intracellular stores. However, extinction of the response to muscarinic agonists did not preclude a response to adrenergic agonists, while the contrary was not true. These results suggest that these agonists liberate Ca2+ from two functionally distinct, caffeine‐insensitive, Ca2+ intracellular stores.
Melatonin attenuates L‐cysteine‐induced seizures and lipid peroxidation in the brain of mice
Authors: Yamamoto Hiro‐aki , Tang Hai‐wang
Published: February 2007

Abstract: The effect of melatonin, a potent free radical scavenger, on L‐cysteine‐induced seizures and lipid peroxidation was investigated in mice. When L‐cysteine (1.25, or 5.0 μmol/animal) was injected intracerebroventricularly (i.c.v.) into mice, severe tonic seizures were observed for over 20 sec in 75% and 100% of the treated mice, respectively. However, when melatonin (20 or 100 mg/kg) was injected subcutaneously (sc) into mice 15 min before L‐cysteine injection (1.25 umol/animal, i.c.v.), the incidence of seizures was observed in only 35% and 20% of the treated mice, respectively. Furthermore, when L‐cysteine (1.25 or 5.0 (amol/animal, i.c.v.) was injected into mice, lipid peroxidation in whole brain 20 min after injection was significantly increased by 56% or 67% as compared to that of the control. However, when the seizures induced by L‐cysteine (1.25 μmol/animal) were abolished by preadminstration of melatonin, the increased lipid peroxidation induced by L‐cysteine was prevented. These results suggest that there may be a positive correlation between free radical formation and seizures induced by L‐cysteine and that melatonin affords protection against the seizures as well as against the associated lipid peroxidation.
Characteristics of the plasma melatonin rhythm are not modified by steroids during the estrous cycle in Ile‐de‐France ewes
Authors: Zarazaga Luis A. , Malpaux Benoit , Chemineau Philippe
Published: February 2007

Abstract: Two experiments were designed to determine whether gonadal steroids during the estrous cycle may modify the characteristics of the plasma melatonin rhythm. In the first experiment, 12 ovariectomized estradiol‐treated ewes were used and exposed to constant short days. The experimental design was a latin square to distinguish between steroid treatments and individual effects on melatonin secretion. Twenty four hours before the bleeding period (hourly during 20 hr) and with a 1 week interval, animals were treated with a) additional subcutaneous estradiol implants, b) progesterone devices, or c) control. In the second experiment, nine ewes received a treatment combining fluorogestone acetate devices and pregnant mare serum gonadotrophin to induce synchronous ovulations. Samples for melatonin determination were obtained hourly for 13 hr at three stages of estrous cycle: follicular phase, early luteal phase, and late luteal phase. Ovarian activity was monitored by taking daily samples for progesterone analysis and ovulation rate was determined by laparoscopy. Duration and mean melatonin plasma concentrations of the elevation were calculated for each ewe and each night and analysed by latin square test (experiment 1) or ANOVA (experiment 2). Melatonin concentrations of elevation and duration of elevation were not significantly affected by hormonal treatments or by phase of estrous cycle. A strong individual effect was detected (P<0.01) for both parameters in both experiments. It was concluded that melatonin secretion is unaffected by steroid administration or by phase of estrous cycle. The existence of very high inter‐individual variation suggest that both parameters are individual characteristics of each animal which may have a strong genetic basis.
Calretinin immunoreactivity in pineal gland of different mammals including man
Authors: Novier Alain , Nicolas Dominique , Krstic Radivoj
Published: February 2007

Abstract: Calretinin (CR) is a calcium‐binding protein, found in a variety of organs and systems such as the central nervous system and the pineal gland. It was first thought to be a specific neuronal marker but this selectivity is now in question since CR has been demonstrated in avian thymus, rat ovary, rat and guinea pig inner ear, rat testis, and chicken and rat pineal gland. To contribute to the knowledge of the presence of CR‐positive cells in the pineal parenchyma of rat and other mammalian including man, we performed immunocytochemistry on pineal glands of gerbils, rats, goats, cows, and humans, using a CR anti‐serum. To confirm it was actually CR that was demonstrated, we performed Western Blot analyses. Finally, to precisely identify the nature of CR‐positive cells we accomplished double‐labelling immunofluorescence, using antisera against some nerve cell specific cytosquelettal proteins such as MAP‐5, MAP‐2, NF‐L, NF‐M, and NF‐H. CR‐positive cells were found in all pineal glands studied. These cells all possess a round, oval, or polygonal‐shaped perikaryon sending one or more processes of different lengths into the glandular parenchyma. There is a lack of CR immunoreactivity in the nucleus and cell organelles while the cytosol contains a high concentration of this protein. Nevertheless, there are some slight differences between species, especially concerning the number of reactive cells and their relationships with different parenchymal structures such as blood vessels or acervuli. Among the CR‐positive cells, only a few were actually nerve cells, contributing probably to an intrinsic innervation of the gland. The remaining CR‐reactive cells seem to correspond mostly to pinealocytes in a specific histophysiological state and possibly to neuron‐like cells. The significance of the CR‐positive cells in the pineal glands remains to be elucidated.
Ontogeny of pineal melatonin rhythm in rats under 12: 12‐hr and 14: 14‐hr lightdark conditions
Authors: Laakso Maija‐Liisa , Alila Aino , Hätönen Taina , Mustanoja Satu M.
Published: February 2007

Abstract: The aim of the study was to determine whether a discrepancy between the genetically determined endogenous circadian period and an abnormally long Zeitgeber period disturbs the development of melatonin synthesis. Breeding pairs of rats were kept under 12: 12‐ or 14: 14‐hr light: dark (LD) conditions. Pineal melatonin contents in the offspring were measured by radioimmunoassay. At 2 weeks of age high melatonin contents were found from lights‐off to lights‐on in both conditions suggesting dominance of the photic regulation. At 3 weeks of age the signs of the circadian regulation in the melatonin profiles were evident: a lag period after the light offset in control conditions and a significant decline before the light onset in both conditions. However, in 14: 14‐hr LD conditions the melatonin content did not decrease to daytime levels until the lights were on. This could suggest incomplete maturation of the circadian system. The phase relationships between the melatonin peak and LD cycle were different in the two conditions. A statistically significant LD difference was first found at the age of 8–10 days in male pups and at 14 days in female pups under both lightings. The results suggest that the abnormally long LD cycle did not cause any major disorders in the development of photic or circadian regulation of the melatonin synthesis.
Melatonin reduces mortality from Aleutian disease in mink (Mustela vison)
Authors: Ellis LeGrande C.
Published: February 2007

Abstract: Aleutian disease (AD) results from a persistent parvoviral infection that results in marked hypergammaglobulinemia and immune complex mediated lesions of the kidney, liver, lungs and, arteries. Melatonin protected both a wild type or demi strain and a demi/dark crossed strain of mink from AD. The biogenic amine also afforded protection against other non‐diagnosed diseases naturally found on mink farms when it was available from a subcutaneously‐placed reservoir. Some genetic strains of mink apparently differed in the resistance of mink to the virus and in the protective ability of melatonin. The demi strain was the most resistant followed by pastels, mahogany, darks, and those strains with the double recessive Aleutian gene. The protective action of melatonin appeared to result from melatonin's ability to scavenge free radicals, but it could also be due to the induction of antioxidant enzymes or to the modulation of immunity. Melatonin also protected mink against distemper.
Melatonin secretion in rams maintained in constant darkness depends on the timing of a single 1‐hour light pulse given the previous night
Authors: Ravault J.P. , Chesneau D.
Published: February 2007

Abstract: Previous data have demonstrated that a single 1‐hr light pulse at night affects the secretion of melatonin in the ram if it was given at the appropriate time. This paper reports the effect on melatonin secretion of a 1 ‐hr light pulse given at two different times at night to two groups of rams kept in constant darkness the day following light application. It appears that the animals were able to remember the light pulse if it was given 12 hr but not 9 hr after the lights were turned off. This memory could possibly be stored in the suprachiasmatic nucleus as reported recently in the rat.
Analgesic effects on endogenous melatonin secretion
Authors: Lapwood Keith R. , Bhagat Lakshmi , Simpson Mark P.
Published: February 2007

Lapwood KR, Bhagat L, Simpson MP. Analgesic effects on endogenous melatonin secretion. J. Pineal Res. 1997; 22:20–25. © Munksgaard, Copenhagen

Animal welfare concerns have led to increased demands for use of postoperative analgesia in association with experimental surgery. Such treatment is appropriate provided it has no effect on experimental parameters. In order to assess any effects of analgesics on endogenous melatonin production, groups of six ewes were bled at 30 min intervals for the first 4 hr of darkness a) without analgesic treatment and b) immediately after analgesic administration. Analgesics tested were ketoprofen, phenylbutazone (both non‐steroidal anti‐inflammatory drugs or NSAIDs) and buprenorphine (an opioid). Plasma melatonin was measured by radioimmunoassay and 4 hr secretion profiles computed for each animal. Ketoprofen and buprenorphine treatment reduced mean four hour melatonin secretion profiles by 50.6% (from 1,347.3 to 665.1 pg/ml‐hr) and 38.6% (from 287.8 to 171.3 pg/ml‐hr), respectively. Only in the case of phenylbutazone was the response not statistically significant; hence this drug has been selected as a post‐operative analgesic for future experimental studies involving measurement of melatonin levels.
Nocturnal changes in pineal melatonin synthesis during puberty: Relation to estrogen and progesterone levels in female rats
Authors: Okatani Yuji , Watanabe Kazushi , Morioka Nobuyuki , Hayashi Kazutoshi , Sagara Yusuke
Published: February 2007

Okatani Y, Watanabe K, Morioka N, Hayashi K, Sagara Y. Nocturnal changes in pineal melatonin synthesis during puberty: Relation to estrogen and progesterone levels in female rats. J. Pineal Res. 1997; 22:33—41. © Munksgaard, Copenhagen

Our objective was to evaluate the changes in melatonin synthesis during the peripubertal period in the female rat and to determine the effects of ovarian steroid hormones on melatonin synthesis. Pineal levels of tryptophan, 5‐hydroxytryptamine (5‐HT), melatonin and norepinephrine were determined in female Sprague Dawley rats (between 2 and 12 weeks of age) in the mid‐dark during the daily light/dark cycle. Melatonin levels increased with age, parallel to pineal growth, until 6 weeks of age, when the vaginal opening was found in 66.7% of rats, and significantly decreased until 8 weeks of age, when the vaginal opening was found in all rats. Norepinephrine began to increase earlier and reached a mature level at 4 weeks of age. Treatments with bilateral ovariectomy at 4, 6, and 8 weeks of age resulted in significant increases in melatonin and 5‐HT levels, and significant decrease in tryptophan level at 2 weeks after ovariectomy. Treatments with ovariectomy at 6 weeks of age produced a consistent increase in 5‐HT level and a consistent decrease in tryptophan level until 6 weeks after ovariectomy. However, melatonin levels increased until 2 weeks after ovariectomy, then decreased and reached a control level at 6 weeks after ovariectomy. Subcutaneous implantation of estradiol‐17β capsule and daily subcutaneous injection of estradiol benzoate (E2B) (1.0 |μg, 20 μg) for two weeks in the rats ovariectomized at 4, 6, and 8 weeks of age resulted in significant decreases in melatonin and 5‐HT levels and a significant increase in tryptophan level at 2 weeks after ovariectomy. A smaller dose of E2B (0.1 μg)produced the same effects in the rats ovariectomized at 4, but not at 6 and 8 weeks of age. Administration of progesterone (200 μg/day) for 2 weeks did not produce any significant changes in melatonin, 5‐HT, and tryptophan levels. Norepinephrine levels were not changed by any of the above treatments. These results suggest that estrogen, but not progesterone, can modulate nocturnal pineal melatonin synthesis in peripubertal female rats, and that the decline in the melatonin synthetic activity during the pubertal period might be related to the increasing levels of endogenous estrogen, which is secreted from the maturing ovary. The sites of action of the inhibitory effect of estrogen on the pineal melatonin synthesis may be multiple.
Twenty‐four hour rhythms of serum prolactin, growth hormone and luteinizing hormone levels, and of medial basal hypothalamic corticotropin‐releasing hormone levels and dopamine and serotonin metabolism in rats neonatally administered melatonin
Authors: Esquifino Ana I. , Arce Aguslin , Villanua Maria A. , Cardinali Daniel P.
Published: February 2007

Esquifino AI, Arce A, Villanúa MA, Cardinali DP. Twenty‐four hour rhythms of serum prolactin, growth hormone and luteinizing hormone levels, and of medial basal hypothalamic corticotropin‐releasing hormone levels and dopamine and serotonin metabolism in rats neonatally administered melatonin. J. Pineal Res. 1997; 22:52–58. © Munksgaard, Copenhagen

To obtain information on long‐term circadian consequences of administering melatonin neonatally to rats, we assessed the 24‐hour rhythms of 1) serum prolactin (PRL), luteinizing hormone (LH), and growth hormone (GH), and 2) medial basal hypothalamic dopamine (DA) and serotonin (5‐HT) metabolism and corticotropin‐releasing hormone (CRH) content in 60‐day old male rats injected with 100 μg of melatonin on the 5th day of life. Controls receiving vehicle alone showed serum PRL concentration (when 60 days of age) attaining its maximum at the end of the light period (i.e., at 2000 hr), while in melatonin‐injected rats high PRL values were found between 1200 and 2000 hr. Twenty‐four hour changes in serum LH levels exhibited a maximum at noon, and to a similar extent in vehicle‐ and melatonin‐treated rats. Neonatal melatonin injection did not affect serum GH concentration when the rats were adult. In the medial basal hypothalamus (MBH), the dihydroxyphenyl acetic acid (DOPAC)/DA ratio attained a maximum at midnight, its amplitude being significantly higher in melatonin‐ than in vehicle‐treated rats. Neonatally melatonin‐injected rats also exhibited a second maximum in DOPAC/DA ratio at noon, coinciding with a minimum in DA levels of MBH. The 5‐hydroxyindoleacetic acid (5‐HIAA)/5‐HT ratio in MBH showed significant diurnal variations in vehicle‐injected controls with maxima at 1200 and 0400 hr, while in melatonin‐treated rats a single maximum occurred at 2400 hr. These maxima correlated with minima in 5‐HT content of MBH. Neonatal melatonin injection brought about a significant increase in the CRH content of MBH, as well as distortion of its diurnal rhythmicity, a maximum being found at noon in controls and at 1800 hr in melatonin‐treated rats. The results indicate that exposure to melatonin early in life affects subsequent diurnal rhythmicity of PRL release, and of DA and 5‐HT turnover and CRH content in the MBH of rats.
Effects of melatonin on mammary gland lesions in transgenic mice overexpressing N‐rasproto‐oncogene
Authors: Mediavilla M.D. , Giiezmez A. , Ramos S. , Kothari L. , Garijo F. , Barceló E.J. Sanchez
Published: February 2007

Mediavilla MD, Güezmez A, Ramos S, Kothari L, Garijo F, Sanchez Barcelo EJ. Effects of melatonin on mammary gland lesions in transgenic mice overexpressing N‐ras proto‐oncogene. J. Pineal Res. 1997; 22:86–94. © Munksgaard, Copenhagen.

The oncostatic effects of melatonin on the mammary gland have been studied in transgenic mice carrying the N‐ras proto‐oncogene under the control of the MMTV‐LTR. Female (4‐week‐old) virgin mice with positive transgenic pedigrees were injected with melatonin (200 μg/mouse/ day, five times a week) or vehicle late in the evening. After 5 months of treatment, animals were sacrificed and the mammary glands were dissected for whole mounts, histology, and immunohistochemical analysis with a mouse monoclonal antibody specific for N‐ras protein. Mammary glands of control transgenic mice showed different densities of hyperplastic alveolar nodules (HANs) consisting primarily of dysplastic epithelial cells with nuclear atypia and prominent nucleoli. The epithelial cells of HANs showed a high expression of N‐ras while no immunostaining was detected in the unaffected mammary parenchyma. Only one (10%) of the control transgenic mice presented an infiltrating ductal carcinoma with the neoplastic cells overexpressing N‐ras protein. The mammary glands of melatonin treated mice had a lower density of HANs, absence of epithelial dysplastic cells, and weak immunostaining of N‐ras protein in comparison to the vehicle‐treated group. None of the melatonin treated animals developed mammary carcinomas during the observation period. The lymph nodes of the inguinal mammary glands of all the vehicle‐treated transgenic mice presented hyperplasia and two animals even had lymphomas, whereas in melatonin‐treated animals there was less hyperplasia (two cases were atrophic) and a lack of lymphomas. We conclude that in the mammary glands of MMTV‐LTR/N‐ras transgenic female virgin mice, melatonin a) reduces the incidence of HANs and the expression of N‐ras protein in focal hyperplastic lesions, b) completely prevents the development of epithelial cell atypia and mammary adenocarcinomas, and c) also reduces the hyperplasia of the mammary lymphoid tissue and prevents the development of lymphomas.
Controlled‐release melatonin implants delay puberty in rats without altering melatonin rhythmicity
Authors: Kennaway David J. , Rowe Shawn A.
Published: February 2007

ABSTRACT: There is increasing evidence that continuous availability of melatonin via implants can produce the same physiological changes in animals as timed administration of the hormone. The mechanisms underlying this apparent contradiction are not known. In an attempt to gain further understanding of the way continuous melatonin administration affects reproductive activity, the effects of melatonin implants on gonadal development and melatonin production were investigated in rats treated neonatally with testosterone. Five‐day‐old male rats maintained on a 12L: 12D photoperiod were injected with 1 mg testosterone propionate to induce photo‐responsiveness and implanted at 21 days of age with novel melatonin implants designed to raise the daytime blood melatonin concentration into the nighttime range, i.e., from less than 60 pM in the controls during the day to 380 ± 33 pM in the implanted rats. Following 21 days treatment, seminal vesicle and ventral prostate weights of implanted rats were significantly less than the controls (27.0 ± 1.9 vs. 18.5 ± 1.5 mg/ 100g BW (P= 0.003) and 33.8 ± 2.1 vs. 26.7 ± 2.2 mg/100g BW (P= 0.02), respectively). To determine the effect of the implants upon melatonin production, urine was collected at hourly intervals during the last four days of the experiment and the hourly 6‐sulphatoxymelatonin (aMT.6S) excretion rate was determined. Rats bearing melatonin implants maintained a rhythm of aMT.6S excretion in 12L:12D, which was indistinguishable from that in the control animals except for a raised daytime excretion of the metabolite. Following one cycle of urinary aMT.6S measurements in the light/dark cycle, the animals were released into constant darkness, with the implants still in place or after their removal four hours before darkness to evaluate the characteristics of the melatonin rhythm in the absence of masking effects of the light/dark cycle. The melatonin rhythm persisted in both control and implanted rats and no differences in the onset, offset, or amplitude could be determined. The results of this study indicate that, like many other mammals, for laboratory rats controlled continuous release of melatonin can mimic the effects of short daylength or timed melatonin administration. Despite the reproductive consequences of continuous melatonin delivery, the timing of endogenous melatonin production is unaffected.
Cataractogenesis and lipid peroxidation in newborn rats treated with buthionine sulfoximine: Preventive actions of melatonin
Authors: Li Zhrong Ren , Reiter Russel J. , Fujimori Osamu , Oh Chang Seok , Duan Yan Ping
Published: February 2007

ABSTRACT: The purpose of this study was to examine the influence of exogenously administered melatonin on cataract formation and lipid peroxidation in newborn rats treated with buthionine sulfoximine (BSO), a drug which inhibits the rate‐limiting enzyme in glutathione (GSH) synthesis, y‐glutamylcysteine synthase, thereby depleting animals of their stores of the important intracellular antioxidant, GSH. BSO (3 mmol/kg BW) was given for three consecutive days beginning on postnatal day 2; melatonin (4 mg/kg) was injected daily beginning on postnatal day 2 and continuing until the animals were killed (either day 9 or day 17 after birth). None of the control animals (rats treated with neither BSO nor with melatonin) developed lenticular opacification during the observation period. In the BSO‐treated rats, 16 of 18 animals (89%) had observable cataracts when they were examined. In rats that received both BSO and melatonin, the incidence of cataracts was highly significantly decreased, i.e., only 3 of 18 rats (7%) had observable cataracts. In addition to cataracts, the level of lipid peroxidation products (malondialdehyde (MDA) and 4‐hydroxyalkenals (4‐HDA)) was examined in the lens, brain, liver, lung, and kidney of control and experimental animals. In BSO‐treated rats, the lens, kidney, and lung exhibited increased levels of MDA plus 4‐HDA relative to those measured in the control rats; these increases were reversed in the BSO‐treated rats who were injected with melatonin daily. While BSO administration did not increase basal levels of MDA plus 4‐HDA in either the brain or liver, melatonin reduced levels of lipid peroxidation products below those measured in the control rats (at 17 days after birth). The changes induced by melatonin are consistent with the free‐radical scavenging and antioxidative properties of this indole.
Melatonin‐sensitive, serum‐stimulated signalling in ovine pars tuberalis
Authors: McNulty S. , McNulty T.J. , Schurov I.L. , Morgan RJ. , Hastings M.H.
Published: February 2007

ABSTRACT: In primary cultures of ovine pars tuberalis (oPT), serum acts through melatonin‐sensitive mechanisms independent of cyclic AMP to increase the phosphorylation of the Ca2+/cyclic AMP response element binding protein (CREB). Immunocytochemical and biochemical assays were used to characterize the active components of serum and the signalling pathways through which they and melatonin function in oPT. The stimulatory effect of serum was heat‐labile, sensitive to precipitation by methanol, and required components with a mass greater than 10 KDa implicating peptide or protein factors as the active agent. Serum increased the cytosolic free Ca2+ concentration ([Ca2+]i) of oPT cells. Serum also enhanced the release of [3H]‐choline and [3H]‐arachidonic acid from prelabeled cells, demonstrating that factors present in serum increase the breakdown of cellular phospholipids. This effect, however, was not blocked by melatonin (1 μM). Serum also caused a dose‐dependent increase in levels of immediate early gene immunoreactivity, confirming that factors in serum have the ability to control transcription in the oPT. Down‐regulation of protein kinase C (PKC) by treatment with 12‐0‐tetradecanoylphorbol‐13‐acetate (TPA, 100 nM) or treatment with a specific PKC inhibitor (RO‐31‐8220, 1 μM), did not affect protein kinase A‐mediated stimulation of CREB phosphorylation. However, down‐regulation of PKC blocked the acute stimulatory effects of TPA (100 nM) and of serum (1%). Moreover, RO‐31–8220 abolished the stimulatory effect of TPA (100 nM) and strongly attenuated that of serum (1%). These results demonstrate that serum increases the phosphorylation of CREB by stimulating cyclic AMP‐independent, PKC‐dependent, signalling pathways within the oPT. PKC may be activated through increased phospholipid catabolism and/or raised [Ca2+]i.
Melatonin prevents increases in neural nitric oxide and cyclic GMP production after transient brain ischemia and reperfusion in the Mongolian gerbil (Meriones Unguiculatus)
Authors: Guerrero Juan M. , Reiter Russel J. , Ortiz Genaro G. , Pablos Marta I. , Sewerynek Ewa , Chuang Jih‐lng
Published: February 2007

ABSTRACT: While nitric oxide (NO) has been implicated as a mediator of glutamate excitotoxicity after cerebral ischemia/reperfusion, melatonin has been reported to inhibit brain NO production by suppressing nitric oxide synthase. The purpose of the present studies was to determine the effect of exogenous melatonin administration on NO‐induced changes during brain ischemia/reperfusion. Indicators of cerebral cortical and cerebellar NO production [nitrite/nitrate levels and cyclic guanosine monophosphate(cGMP)] were used to estimate neural changes after transient bilateral carotid artery ligation followed by reperfusion in adult Mongolian gerbils (Meriones unguiculatus). Results show for the first time that melatonin prevents the increases in NO and cGMP production after transient ischemia/reperfusion in frontal cerebral cortex and cerebellum of Mongolian gerbils. The inhibitory effect of melatonin on NO production and its ability to scavenge free radicals and the peroxynitrite anion may be responsible for the protective effect of melatonin on neuronal structures during transient ischemia followed by reperfusion.
Melatonin site and mechanism of action: Single or multiple?
Authors: Cardinali Daniel P. , Golombek Diego A. , Rosenstein Ruth E. , Cutrera Rodolfo A. , Esquifino Ana I.
Published: February 2007

ABSTRACT: By affecting the entrainment pathways of the biologic clock, melatonin has a major influence on the circadian and seasonal organization of vertebrates. In addition, a number of versatile functions that far transcend melatonin actions on photoperiodic time measurement and circadian entrainment have emerged. Melatonin is a free radical scavenger and antioxidant and it has a significant immunomodulatory activity, being presumably a major factor in an organism's defense toxic agents and invading organisms. Besides affecting specific receptors in cell membranes to exert its effects, the interaction of melatonin with nuclear receptor sites and with intracellular proteins, like calmodulin or tubulin‐associated proteins, as well as the direct antioxidant effects of melatonin, may explain many general functions of the pineal hormone.