Dietary supplementation with melatonin reduces levels of amyloid beta-peptides in the murine cerebral cortex

Melatonin levels decrease with aging in mice. Dietary supplementation with melatonin has recently been shown to result in a significant rise in levels of endogenous melatonin in the serum and all other tissue samples tested. Herein, the effects of dietary melatonin on brain levels of nitric oxide synthase, synaptic proteins and amyloid beta-peptides (Abeta) were determined in mice. Melatonin supplementation did not significantly change cerebral cortical levels of nitric oxide synthase or synaptic proteins such as synaptophysin and SNAP-25. Increased brain melatonin concentrations however, led to a significant reduction in levels of toxic cortical Abeta of both short and long forms which are involved in amyloid depositions and plaque formation in Alzheimer's diseases. Thus, melatonin supplementation may retard neurodegenerative changes associated with brain aging. Depletion of melatonin in the brain of aging mice may in part account for this adverse change.

Melatonin increases anagen hair rate in women with androgenetic alopecia or diffuse alopecia: results of a pilot randomized controlled trial

BACKGROUND

In addition to the well-known hormonal influences of testosterone and dihydrotestosterone on the hair cycle, melatonin has been reported to have a beneficial effect on hair growth in animals. The effect of melatonin on hair growth in humans has not been investigated so far.

OBJECTIVES

To examine whether topically applied melatonin influences anagen and telogen hair rate in women with androgenetic or diffuse hair loss.

METHODS

A double-blind, randomized, placebo-controlled study was conducted in 40 women suffering from diffuse alopecia or androgenetic alopecia. A 0.1% melatonin or a placebo solution was applied on the scalp once daily for 6 months and trichograms were performed to assess anagen and telogen hair rate. To monitor effects of treatment on physiological melatonin levels, blood samples were taken over the whole study period.

RESULTS

Melatonin led to a significantly increased anagen hair rate in occipital hair in women with androgenetic hair loss compared with placebo (n=12; P=0.012). For frontal hair, melatonin gave a significant increase in the group with diffuse alopecia (n=28; P=0.046). The occipital hair samples of patients with diffuse alopecia and the frontal hair counts of those with androgenetic alopecia also showed an increase of anagen hair, but differences were not significant. Plasma melatonin levels increased under treatment with melatonin, but did not exceed the physiological night peak.

CONCLUSIONS

To the authors' knowledge, this pilot study is the first to show that topically applied melatonin might influence hair growth in humans in vivo. The mode of action is not known, but the effect might result from an induction of anagen phase.

Influence of oral melatonin on natural and gonadotropin-induced ovarian function in the domestic cat

Ovarian hyperstimulation after exogenous gonadotropin stimulation is believed to be a cause of poor success after artificial insemination (AI) in felids. The objectives of this study were to assess the effect of oral melatonin on endogenous ovarian activity in the domestic cat and subsequent eCG/hCG-induced ovarian activity. Serum melatonin concentrations peaked approximately 1h after a single oral dose of 30 mg melatonin and remained elevated above endogenous day-time concentrations for >8h. The calculated circulating half-life (mean +/- S.E.M) of oral melatonin was 45.4+/-3.5 min, and the elimination rate constant (k(10)) was 55.2+/-4.2 min(-1). Oral melatonin (30 mg per day) administered 3h before lights-off effectively and reversibly suppressed estrous elevations in fecal estrogens after 25 days of treatment. There was a progressive decrease in baseline estrogen concentrations from inter-estrous concentrations after 25 days of treatment to below inter-estrous concentrations after 35 days of treatment. Oral melatonin treatment (30 mg per day for 30 days) prior to eCG/hCG administration only marginally reduced ancillary follicle development and had no significant effect on the quantity or quality of embryos produced by AI. Thus, oral melatonin effectively inhibited endogenous ovarian activity and had no adverse impact on embryo quality after AI in the domestic cat; however, this treatment was only marginally effective in minimizing eCG/hCG-induced ovarian hyperstimulation.

Photoperiodic regulation of type 2 deiodinase gene in Djungarian hamster: possible homologies between avian and mammalian photoperiodic regulation of reproduction

The molecular mechanisms responsible for seasonal time measurement have yet to be fully described. Recently, we used differential analysis to identify that the type 2 iodothyronine deiodinase (Dio2) gene is responsible for the photoperiodic response of gonads in Japanese quail. It was found that expression of Dio2 in the mediobasal hypothalamus is induced by light and that T(3) content in the mediobasal hypothalamus increased under long day conditions. In addition, we showed that intracerebroventricular infusion of T(3) mimics photoperiodically induced testicular growth. Because it is well known that thyroid hormone is also essential for the maintenance of the seasonal reproductive changes in a number of mammals, we examined expression of Dio2 in Djungarian hamsters and found expression in the ependymal cell layer lining the infralateral walls of the third ventricle and the cell-clear zone overlying the tuberoinfundibular sulcus. Signal intensity was high under long days and weak under short days. Although light pulse did not affect Dio2 expression, melatonin injections decreased Dio2 expression under long days. These results indicate that Dio2 may be involved in the regulation of seasonal reproduction in mammals in the same way as observed in birds.

Inhibitory effect of melatonin on alpha1-adrenergic-induced vasoconstriction in mesenteric beds of spontaneously hypertensive rats

BACKGROUND

The aim of this study was to assess the effects of melatonin on alpha1-adrenergic pathway in mesenteric arteries of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats.

METHODS AND RESULTS

The SHR are characterized by a higher vasoconstriction (P < .001) and inositol phosphate formation (P < .001) in response to phenylephrine (PHE) and an increased superoxide anion production (P < .001) in mesenteric arteries. Melatonin and 2-iodomelatonin produced a significant inhibition of the PHE-induced vasoconstriction in isolated and perfused mesenteric beds (P < .001) with the same magnitude in SHR and WKY rats. Melatonin significantly decreased the inositol phosphate (IPs) formation in isolated mesenteric arteries from SHR compared to WKY rats (P < .001). The inhibitory effect of melatonin was increased by the removal of endothelium (P < .001). No effects of superoxide dismutase (SOD), tempol, or catalase were observed on the PHE-induced vasoconstriction. Moreover, no superoxide anion scavenging effect of 2-iodomelatonin was observed in isolated mesenteric vascular muscle cells using lucigenin.

CONCLUSIONS

The present study showed that high melatonin concentrations inhibit the alpha1-adrenergic-induced vasoconstriction and inositol phosphate formation in mesenteric arteries from SHR and WKY rats. The vasorelaxant effect of the melatonin receptors agonist, 2-iodomelatonin, and the absence of any vasoactive effect of antioxidants such as SOD, tempol, and catalase suggest that melatonin exerts its inhibition on alpha1-adrenergic-induced vasoconstriction of mesenteric arteries through a low-affinity membrane receptor negatively coupled to the IPs formation and that this effect is independent of its antioxidant properties.

Melatonin precursor; L-tryptophan protects the pancreas from development of acute pancreatitis through the central site of action

Melatonin, produced from L-tryptophan, protects the pancreas against acute damage by improving the antioxidative status of tissue. Melatonin receptors have been detected in the brain, but the contribution of these receptors to the pancreatic protection is unknown. The aim of our study was to compare the effects of melatonin precursor; L-tryptophan given intracerebroventricularly (i.c.v.) or intraperitoneally (i.p.) on the course of acute pancreatitis. Acute pancreatitis was induced by subcutaneous infusion of caerulein (5 microg/kg-h x 5 h). L-tryptophan was given i.p. (2.5, 25 or 250 mg/kg) or administered into right cerebral ventricle (0.02, 0.2 or 2.0 mg/rat) 30 min prior to the start of caerulein infusion. Plasma amylase, lipase and TNF alpha activities were measured to determine the severity of caerulein-induced pancreatitis (CIP). The lipid peroxidation products: malonylodialdehyde and 4-hydroksynonenal (MDA + 4-HNE) and activity of superoxide dismutase (SOD) were measured in the pancreas of intact or CIP rats with or without L-tryptophan pretreatment. Melatonin blood level was measured by RIA. CIP was confirmed by histological examination and manifested as an edema and rises of plasma levels of amylase, lipase and TNF alpha (by 550%, 1000% and 600%). MDA + 4-HNE was increased by 600%, whereas SOD activity was reduced by 75% in the pancreas of CIP rats. All manifestations of CIP were significantly reduced by pretreatment of the rats with L-tryptophan given i.c.v. at doses of 0.2 or 2.0 mg/rat, or by peripheral administration of this amino acid used at dose of 250 mg/kg i.p. In control rats plasma level of melatonin averaged about 40 +/- 2 pg/ml and was not significantly affected by CIP, by central application of L-tryptophan (0.02, 0.2 or 2.0 mg/rat) or by peripheral administration of this melatonin precursor used at doses of 2.5 or 25 mg/kg i.p. Plasma melatonin level was markedly increased by pretreatment of the rats with L-tryptophan given i.p. at dose of 250 mg/kg. We conclude that central administration of melatonin precursor; L-tryptophan, as well as peripheral application of high dose of this melatonin precursor prevented the pancreatic damage produced by CIP. The favorable effect of peripherally administered L-tryptophan could be related to the rise of melatonin plasma level and to pancreatoprotective action of this indoleamine. The beneficial effect of centrally administered L-tryptophan could be mediated through activation of central receptors for locally produced melatonin.

Opposite effects of zinc and melatonin on thyroid hormones in rats

The present study was conducted to investigate how thyroid function in rats is affected by administration of 3 mg per kg per day of zinc and/or melatonin. The study was conducted with 40 Sprague-Dawley adult male rats equally divided into four groups: 1 (controls), 2 (zinc-only), 3 (melatonin-only) and 4 (zinc- and melatonin-supplemented). The supplementation was continued for 4 weeks after which the animals were sacrificed and plasma samples were obtained for determination of zinc, melatonin, free- and total triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH) levels. The free T3, T4 and TSH levels were lower in the melatonin group than in all other groups (P<0.01), while free- and total T3 levels were higher in the zinc group (P<0.01). The group that received zinc and melatonin combined had free thyroid hormone levels higher than the only melatonin group. These results show that melatonin has a thyroid function suppressing action, just the opposite to the actions of zinc. When zinc is administered along with melatonin, its thyroid function suppression is diminished.

HaCaT cell proliferation influenced by melatonin

The hormone melatonin is characterized by numerous pharmacological effects. The influence of melatonin on the growth of the human hair follicle was shown in previous investigations. In the present study, the effects of melatonin were investigated by means of proliferation tests of HaCaT keratinocytes using the [3H]thymidine incorporation, a fluorescence assay with Hoechst dye 33342 and the ATP bioluminescence assay. The aim of the study was to find melatonin concentrations suitable for treatments of the skin and whether there is a cytotoxic effect on HaCaT cells. The different proliferative activity of melatonin depending on its concentration and the time of incubation could be shown in all investigations.

Melatonin uptake and growth prevention in rat hepatoma 7288CTC in response to dietary melatonin: melatonin receptor-mediated inhibition of tumor linoleic acid metabolism to the growth signaling molecule 13-hydroxyoctadecadienoic acid and the potential role of phytomelatonin

Both physiological and pharmacological levels of the pineal hormone melatonin exhibit substantial anticancer activity in tissue-isolated rat hepatoma 7288CTC via melatonin receptor-mediated blockade of tumor uptake of linoleic acid (LA) and its metabolism to the mitogenic signaling molecule 13-hydroxyoctadecadienoic acid (13-HODE). Melatonin is also present in significant amounts in edible plants and is supplied in nutritional supplements. We confirmed the presence of significant quantities of melatonin in 20 varieties of edible plants. In pinealectomized tumor-free rats, 3 weeks of ingestion of either 5 or 50 microg/day of melatonin contained in a semi-purified diet resulted in a dose-dependent elevation in steady-state plasma melatonin levels within the nocturnal physiological range. In pineal-intact tumor-bearing rats, the daily intake of 5 microg/day of melatonin for 3 weeks resulted in an enhanced amplitude and duration of the nocturnal melatonin levels within physiological circulating limits. The nocturnal melatonin amplitude in rats ingesting 500 ng of melatonin/day remained within the physiological range. A dose-related increase in tumor concentrations of melatonin occurred in animals ingesting melatonin from the diet. Perfusion of tumors in situ with physiological, nocturnal blood levels of melatonin resulted in a mean 31% uptake and retention of the melatonin. Chronic ingestion of 50 ng, 500 ng or 5 microg of melatonin/day supplied in a semi-purified 5% corn oil diet led to a significant dose-dependent reduction in the rates of tumor total fatty acid uptake, LA uptake, 13-HODE production and tumor growth. The co-ingestion of melatonin receptor antagonist S20928 completely blocked the effects and prevented the intra-tumoral accumulation of melatonin. Melatonin receptor-mediated suppression of tumor growth, LA uptake and metabolism, and stimulation of tumor melatonin uptake and retention in response to the dietary intake of phytomelatonin from edible plants or melatonin from nutritional supplements, could play an important role in cancer growth prevention.

Daily nighttime melatonin reduces blood pressure in male patients with essential hypertension

Patients with essential hypertension have disturbed autonomic cardiovascular regulation and circadian pacemaker function. Recently, the biological clock was shown to be involved in autonomic cardiovascular regulation. Our objective was to determine whether enhancement of the functioning of the biological clock by repeated nighttime melatonin intake might reduce ambulatory blood pressure in patients with essential hypertension. We conducted a randomized, double-blind, placebo-controlled, crossover trial in 16 men with untreated essential hypertension to investigate the influence of acute (single) and repeated (daily for 3 weeks) oral melatonin (2.5 mg) intake 1 hour before sleep on 24-hour ambulatory blood pressure and actigraphic estimates of sleep quality. Repeated melatonin intake reduced systolic and diastolic blood pressure during sleep by 6 and 4 mm Hg, respectively. The treatment did not affect heart rate. The day-night amplitudes of the rhythms in systolic and diastolic blood pressures were increased by 15% and 25%, respectively. A single dose of melatonin had no effect on blood pressure. Repeated (but not acute) melatonin also improved sleep. Improvements in blood pressure and sleep were statistically unrelated. In patients with essential hypertension, repeated bedtime melatonin intake significantly reduced nocturnal blood pressure. Future studies in larger patient group should be performed to define the characteristics of the patients who would benefit most from melatonin intake. The present study suggests that support of circadian pacemaker function may provide a new strategy in the treatment of essential hypertension.

Hemorheology, melatonin and pinealectomy. What's the relationship? An experimental study

The circadian rhythm of stroke and myocardial infarction (MI) may be related to the circadian rhythm of melatonin, and erythrocyte deformability may be the key mechanism in this relationship. Therefore, this study has been performed to determine if there is a relationship between the pineal gland and melatonin and red cell deformability. Twenty-eight rats underwent pinealectomy, pinealectomy plus melatonin administration (200 mg/kg), or no treatment (n=7 in each group). Erythrocyte deformability was determined using the filtration technique. The results are reported in mean (+/-SD) seconds: control: 1.45+/-0.44; pinealectomy (A): 1.55+/-0.16; pinealectomy (B): 1.34+/-0.26 and pinealectomy and melatonin: 2.56+/-0.69. Pinealectomy by itself did not cause any statistically significant change in erythrocyte deformability but the addition of melatonin significantly decreased it. These results suggest a relationship between melatonin and erythrocyte deformability. Further investigations may uncover the causes of the circadian rhythm of stroke and MI, which may help improve chronobiological therapies.

Lead induced oxidative stress and its recovery following co-administration of melatonin or N-acetylcysteine during chelation with succimer in male rats

Lead is a ubiquitous element in the environment causing oxidative burst in the exposed individuals leading to tissue damage. Antioxidants have long been known to reduce the free radical-mediated oxidative stress while, thiol chelators have been used to treat arsenic toxicity. The therapeutic efficacy of melatonin or N-acetylcysteine (NAC) was studied in the present study, both individually and in combination with a potent thiol-chelating agent, meso 2,3-dimercaptosuccinic acid (DMSA), in reducing lead concentration in blood and other soft tissues. Their ability to restore altered haematopoietic, hepatic and other biochemical variables indicative of tissue oxidative stress in male rats was also investigated. Administration of melatonin and NAC individually, provided significant protection to lead induced disturbed antioxidant defense that may significantly compromise normal cellular function. Administration of melatonin and NAC also provided a significant protection to thiobarbituric acid reactive substances (TBARS) levels, reduced glutathione (GSH) and oxidized glutathione (GSSG) contents in tissues, suggesting their ability to act as a free radical scavenger and in protecting cells against toxic insult. NAC, a thiol containing antioxidant, has been used under several clinical conditions with few adverse side effects. It has a high toxicity threshold and its wide therapeutic window enhances its utility. The antioxidant action of NAC is due to its ability to interact with reactive oxygen species (ROS) or its ability to stimulate endogenous glutathione (GSH) synthesis. DMSA, on the other hand when given alone, provided significant recovery in restoring the altered lead sensitive biochemical indices like blood delta-aminolevulinic acid dehydratase (ALAD), urinary delta-aminolevulinic acid (ALA), beside increasing urinary lead excretion and decreasing lead concentration in blood and soft tissues. Interestingly, combined treatment of DMSA and NAC provided more pronounced efficacy in restoring altered biochemical variables and in reducing body lead burden than monotherapy with DMSA. The results thus, suggest the involvement of ROS in lead toxicity and a pronounced beneficial role of NAC in therapeutic implications of lead poisoning when co-administered with a thiol chelator (DMSA) supporting the hypothesis that cellular redox status may be significantly reversed by utilizing a thiol containing antioxidant compound. It can be concluded that, combined therapy with an antioxidant moiety and a thiol-chelating agent may be a better choice for treating plumbism.

Pharmacological effects of melatonin on reproductive activity: experimental bioimplants with sustained-release polymeric systems

A vast literature documents the role of melatonin in human reproductive function including: a) the relation between melatonin and the menstrual cycle in relation to the peak time of luteinizing hormone in the middle of the cycle; b) the varying concentrations of melatonin in the control of puberty; c) the fewer conceptions in some artic populations where melatonin is connected significantly to seasonal photoperiodicity during the months of the polar nights. The aim of this paper is to report our findings on the pharmacological action of this molecule on reproduction in which gonadal activity is clearly connected to photoperiodicity. We used polymer bioimplants programmed for the sustained release of melatonin for experimental gynecologic protocols. These implants had beneficial results with respect to the use of progestinics because melatonin allowed ovarian activity to be induced for at least two to three consecutive cycles with one single bioimplant. We thought it indispensable to use pharmacological systems with a sustained release because different preliminary tests showed that the half-life of melatonin is limited at maximum to two to three hours and, consequently, any other tested modalities of administration would not provide any appreciable results for our study. As a model for our research we used goats to administer melatonin via targeted programs since these animals clearly respond (even against the rule of the light/dark relation) in contrast to humans in whom response is less evident. For controls, after inserting bioimplants in the animals, we tested their efficiency in vitro and subsequently in vivo, evaluating blood parameters and pharmacological effects of melatonin occurring during the treatment. The final results proved to be interesting in relation to reproductive activity in that regular and programmed births were achieved.

Melatonin prevents disruption of hepatic reactive oxygen species metabolism in rats treated with carbon tetrachloride

We reported that melatonin prevents the progression of carbon tetrachloride (CCl4)-induced acute liver injury in rats possibly by attenuating enhanced lipid peroxidation and reduced glutathione depletion. Herein, we examined the effect of melatonin on the changes in hepatic reactive oxygen species (ROS) metabolism in rats with a single intraperitoneal injection of CCl4 (1.6 g/kg body weight); the intent was to clarify the therapeutic mechanism of the indoleamine on CCl4-induced acute liver injury. Rats with and without CCl4 treatment received a single oral dose of melatonin (10, 50 or 100 mg/kg body weight) 6 hr after CCl4 treatment. Hepatic concentrations of ascorbic acid (ASC) and vitamin E (VE) and hepatic activities of superoxide dismutase (SOD), catalase (CAT), Se-glutathione peroxidase (Se-GSH-Px), glutathione reductase (GSSG-R), glucose-6-phosphate dehydrogenase (G-6-PDH), and xanthine oxidase (XO) were determined 6 and 24 hr after CCl4 treatment. The liver of CCl4-treated rats showed reductions in ASC concentrations, and SOD activity and an increase in G-6-PDH activity at 6 hr after treatment and further decreases in ACS concentrations and SOD activity and also further increase in G-6-PDH activity in addition to decreases in CAT and GSSG-R activities and increases in VE concentrations and XO activity at 24 hr after treatment. Melatonin attenuated the reductions in hepatic ASC concentrations and SOD, CAT and GSSG-R activities and the increase in hepatic XO activity in a dose-dependent manner without affecting either hepatic Se-GSH-Px activity or the increased hepatic VE concentration and G-6-PDH activity at 24 hr after CCl4 treatment. No dose of melatonin influenced hepatic ACS and VE concentrations and SOD, CAT, Se-GSH-Px, G-6-PDH, and XO activities in CCl4-untreated rats. These results indicate that melatonin postadministered at pharmacological doses prevents the disruption of hepatic ROS metabolism associated with ASC, SOD, CAT, GSSG-R, and XO, in addition to reduced glutathione, in CCl4-treated rats.

AGING AND VESTIBULAR SYSTEM: SPECIFIC TESTS AND ROLE OF MELATONIN IN COGNITIVE INVOLVEMENT

Balance disorders are frequent with aging. They are particularly important because they decrease social autonomy of the aged subjects and they often provoke falls. The cause is always multifactorial. There is evidence that aging affects multiple sensory inputs, as well as the muscoloskeletal system and central nervous system ability to perform sensorimotor integration. For the evaluation of decreased balance skills in elderly, a specific questionnaire has been prepared, in order to identify high risk of falling called falling risk inventory (FRI) questionnaire, and a complex psycho-sensory-motor test has been studied by means of posturography, in order to detect specific vestibular impairment. Regarding ethiopathogenesis of balance disorders in aged subjects, because the decline of behavioral and cognitive performances are due also to decline of biological rhythm control, the role of melatonin (the hormone regulating circadian rhythms, being strictly connected with cerebellar function, and it is well known that cerebellum acts in elderly both at motor and cognitive regulation. The goals of the present paper are: (i) To present a self-administered FRI questionnaire aimed at identifying possible causes of falls and quantifying falling risk in aged. (ii) To validate posturography as a specific test to investigate vestibular involvement in elderly in correlation with FRI. (iii) To present a complex behavioral test (NT) aimed at evaluating both spatial orientation and spatial memory in elderly, factors involved into the genesis of complex dizziness and unsteadiness. (iv) To evaluate the role of melatonin in cognitive involvement in dizzy, old subjects due to the functional correlations between circadian rhythms, cerebellum balance disturbances and cognitive disorders. General conclusions are: FRI correlates with falling risk. Posturography identifies specific vestibular impairments correlated to balance disorders and elderly falls. Spatial orientation is altered in about 40% of dizzy patients but no significant differences are revealed in melatonin rhythm. Spatial memory is highly altered only in subjects with inversion of circadian melatonin rhythm it is possible to hypothesize that the alteration of the normal circadian melatonin rhythm plays some role in the genesis of dizziness in a subpopulation of patients.

[Comparative effectiveness of antioxidant melatonin and radioprotectors indralin and phenylephrine in local radiation injuries]

In experiments on mice radioprotective properties of indraline, phenyleprine and melatonin were compared at topical application as an ointment at a place of local exposure of animal hind to a dose of 38.3 Gy of 60Co gamma-quanta. Factor of dose reduction was 1.27-1.32 for indraline (1-10% ointment) and 1.29 for phenyleprine (0.25% ointment). Antioxidants were low efficient at radiation skin burn. At later local radiation injuries, such as hind contracture, the efficiency of indraline was 1.33-1.5, that of phenyleprine was 1.28, and that of melatonine (2 and 5% ointment) was 1.23-1.47.

Caffeine or melatonin effects on sleep and sleepiness after rapid eastward transmeridian travel

We measured the effects of slow-release caffeine (SRC) and melatonin (Mlt) on sleep and daytime sleepiness after a seven-time zone eastbound flight. In a double-blind, randomized, placebo-controlled study, each of three groups of nine subjects was given either 300 mg SRC on recovery day 1 (D1) to D5 (0800) or 5 mg Mlt on preflight D-1 (1700), flight day D0 (1600), and from D1 to D3 (2300), or placebo (Pbo) at the same times. Nighttime sleep was evaluated by polysomnography and daytime sleepiness from measurements of sleep latencies and continuous wrist actigraphy. Compared with baseline, we found a significant rebound of slow-wave sleep on night 1 (N1) to N2 under Pbo and Mlt and a significant decrease in rapid eye movement sleep on N1 (Pbo) and N1-N3 (Mlt). Sleepiness was objectively increased under Pbo (D1-D6) and Mlt (D1-D3). SRC reduced sleepiness but also tended to affect sleep quality until the last drug day. In conclusion, both drugs have positive effects on some jet lag symptoms after an eastbound flight: SRC on daytime sleepiness, and Mlt on sleep.

Melatonin in patients with reduced REM sleep duration: two randomized controlled trials

Recent data suggest that melatonin may influence human physiology, including the sleep-wake cycle, in a time-dependent manner via the body's internal clock. Rapid-eye-movement (REM) sleep expression is strongly circadian modulated, and the impact of REM sleep on primary brain functions, metabolic processes, and immune system function has become increasingly clear over the past decade. In our study, we evaluated the effects of exogenous melatonin on disturbed REM sleep in humans. Fourteen consecutive outpatients (five women, nine men; mean age, 50 yr) with unselected neuropsychiatric sleep disorders and reduced REM sleep duration (25% or more below age norm according to diagnostic polysomnography) were included in two consecutive, randomized, double-blind, placebo-controlled, parallel design clinical trials. Patients received 3 mg melatonin daily, administered between 2200 and 2300 h for 4 wk. The results of the study show that melatonin was significantly more effective than placebo: patients on melatonin experienced significant increases in REM sleep percentage (baseline/melatonin, 14.7/17.8 vs. baseline/placebo, 14.3/12.0) and improvements in subjective measures of daytime dysfunction as well as clinical global impression score. Melatonin did not shift circadian phase or suppress temperature but did increase REM sleep continuity and promote decline in rectal temperature during sleep. These results were confirmed in patients who received melatonin in the second study (REM sleep percentage baseline/placebo/melatonin, 14.3/12.0/17.9). In patients who received melatonin in the first study and placebo in the second, the above mentioned effects outlasted the period of melatonin administration and diminished only slowly over time (REM sleep percentage baseline/melatonin/placebo, 14.7/17.8/16.2). Our findings show that exogenous melatonin, when administered at the appropriate time, seems to normalize circadian variation in human physiology. It may, therefore, have a strong impact on general health, especially in the elderly and in shift workers.

Melatonin for treatment of REM sleep behavior disorder in neurologic disorders: results in 14 patients

OBJECTIVE

To describe the treatment response with melatonin for rapid eye movement (REM) sleep behavior disorder (RBD) associated with other neurologic disorders.

BACKGROUND

Clonazepam has been considered the treatment of choice for RBD. However, an alternative treatment is desirable for those with RBD refractory to clonazepam, for those who experience intolerable side-effects with clonazepam, and for those in whom clonazepam precipitates or aggravates obstructive sleep apnea (OSA). To date, there is minimal published data and limited follow-up regarding the use of melatonin for patients with RBD associated with other neurologic syndromes and disorders.

DESIGN/METHODS

The response to melatonin treatment for RBD was reviewed on consecutive patients the investigators treated with this agent at Mayo Clinic Rochester from January 2000 to June 2001. The coexisting neurologic disorders, reasons for using melatonin, effective doses, side-effects, and duration of follow-up were also reviewed on all patients.

RESULTS

Fourteen patients were commenced on melatonin over the specified time period (13 male, median RBD onset age 56 years, range 20-77 years). The coexisting neurologic findings/disorders were dementia with Lewy bodies (n=7), mild cognitive impairment with mild parkinsonism (n=2), multiple system atrophy (n=2), narcolepsy (n=2), and Parkinson's disease (n=1). The reasons for using melatonin in these cases were incomplete response of RBD to clonazepam in six patients, existing cognitive impairment in five, intolerable side-effects with clonazepam in two, and presence of severe obstructive sleep apnea and narcolepsy in one. With seven patients continuing to use clonazepam at 0.5-1.0 mg/night, RBD was controlled in six patients, significantly improved in four, and initially improved but subsequently returned in two; no improvement occurred in one patient and increased RBD frequency/severity occurred in one patient. The effective melatonin doses were 3 mg in two cases, 6 mg in seven cases, 9 mg in one case, and 12 mg in two cases. Five patients reported side-effects, which included morning headaches (2), morning sleepiness (2), and delusions/hallucinations (1); these symptoms resolved with decreased dosage. The mean duration of follow-up was 14 months (range 9-25 months), with eight patients experiencing continued benefit with melatonin beyond 12 months of therapy.

CONCLUSIONS

In this series, persistent benefit with melatonin beyond 1 year of therapy occurred in most but not all patients. Melatonin can be considered as a possible sole or add-on therapy in select patients with RBD. Prospective, long-term, controlled trials with melatonin are warranted in a larger number of patients with RBD associated with a variety of neurologic symptoms and disorders.

Impact of melatonin, zaleplon, zopiclone, and temazepam on psychomotor performance

INTRODUCTION

Modern military operations may require pharmaceutical methods to sustain alertness and facilitate sleep in order to maintain operational readiness. In operations with very limited sleep windows, hypnotics with very short half-lives (e.g., zaleplon, t(1/2) 1 h) are of interest, while with longer sleep opportunities, longer acting agents (e.g., zopiclone, temazepam (t(1/2) 4-6 hours) may be used. This study was designed to compare the effect of a single dose of zaleplon, zopiclone, temazepam, and melatonin on psychomotor performance and to quantify the post-ingestion time required for return to normal performance.

METHOD

There were 23 subjects (9 men, 14 women), 21-53 yr of age, assessed for psychomotor performance on 2 test batteries (4 tasks) that included a sleepiness questionnaire. Psychomotor testing was conducted prior to, and for 7 h after, ingestion of a single dose of each of placebo, zaleplon 10 mg, zopiclone 7.5 mg, temazepam 15 mg, and time-released melatonin 6 mg. The experimental design was a double-blind cross-over with counter-balanced treatment order.

RESULTS

Zaleplon, zopiclone, and temazepam impaired performance on all four tasks: serial reaction time (SRT), logical reasoning (LRT), serial subtraction (SST), and multitask (MT). Melatonin did not impair performance on any task. The time to recovery of normal performance for SRT during the zaleplon, zopiclone and temazepam conditions were 3.25, 6.25, and 5.25 h respectively; for LRT were 3.25, >6.25, and 4.25 h; for SST were 2.25, >6.25, and 4.25 h, and for MT were 2.25, 4.25, and 3.25 h. The recovery time to baseline subjective sleepiness levels for zaleplon, zopiclone, temazepam, and melatonin were 4.25, >6.25, 5.25, and >4.25 h, respectively.

CONCLUSIONS

In spite of a prolonged period of perceived sleepiness, melatonin was superior to zaleplon in causing no impact on performance. The remaining drugs listed in increasing order of performance impact duration are zaleplon, temazepam, and zopiclone.

Pineal control of immune status and hematological changes in blood and bone marrow of male squirrels (Funambulus pennanti) during their reproductively active phase

In addition to pineal control of reproduction in seasonal breeders, melatonin is also known to influence various immune parameters. In the present experiment, we assessed the effect of exogenous melatonin treatment on different hematological parameters of peripheral blood and bone marrow cells, together with histological observations of spleen and thymus blastogenic response and stimulation ratio, and hormonal assays (melatonin and testosterone) of Indian palm squirrel (Funambulus pennanti) during their reproductively active phase when endogenous melatonin levels are low. Daily subcutaneous injection of melatonin (25 microg/100 g body mass.) at 17.30-18.00 h to adult male squirrels for 60 consecutive days during May-June significantly increased the lymphocyte count of blood and bone marrow and the blastogenic response/percent stimulation ratio of spleen and thymus. Histological observation showed densely packed thymocytes and splenocytes. During this period, peripheral testosterone level was high and melatonin was low establishing an inverse relationship as noted earlier for this squirrel. In pinealectomized squirrels, decreased total leukocyte count and percent lymphocyte count in peripheral blood and bone marrow, along with a decreased cell density in spleen and thymus was observed histologically. Further, melatonin treatment of pinealectomized squirrels resulted in restoration of the immune parameters in line with a normal control level. We suggest that during the reproductively active period of male Indian palm squirrels the lymphoid organs were sensitive to melatonin; hence, the exogenous melatonin treatment had an immuno-enhancing effect.

Effects of caffeine intake on the pharmacokinetics of melatonin, a probe drug for CYP1A2 activity

AIMS

The aim of this study was to assess the influence of concomitant caffeine intake on the pharmacokinetics of oral melatonin, a probe drug for CYP1A2 activity.

METHODS

Twelve healthy subjects, six smokers and six nonsmokers, were given melatonin (6 mg) either alone or in combination with caffeine (3 x 200 mg). Blood samples for the analysis of melatonin or caffeine and paraxanthine were taken from 1 h before until 6 h after intake of melatonin. Subjects were genotyped with respect to the CYP1A2*1F (C734A) polymorphism.

RESULTS

When caffeine was coadministered the Cmax and AUC of melatonin were increased on average by 142% (P = 0.001, confidence interval on the difference 44, 80%) and 120% (P < 0.001, confidence interval on the difference 63, 178%), respectively. The inhibitory effect of caffeine was more pronounced in nonsmokers and in individuals with the *1F/*1F genotype.

CONCLUSION

The results of this study revealed a pronounced effect of caffeine on the bioavailability of orally given melatonin, most probably due to inhibition of CYP1A2 activity.

The relationship between bone metabolism, melatonin and other hormones in sham-operated and pinealectomized rats

OBJECTIVE

The influence of pinealectomy and long-term melatonin (MEL) administration on circadian oscillations of selected biochemical markers of bone metabolism [serum alkaline phosphatase (ALP) activity, carboxyterminal propeptide type I procollagen (PICP) and carboxyterminal telopeptide type I collagen (ICTP) concentrations as well as urinary excretion of hydroxyproline (HYP) and Ca] and possible involvement of circadian secretion of IGF-I, parathyroid, thyroid, adrenal cortex and gonads function in this mechanism was evaluated.

METHODS

Studies were performed in 192 adult male Wistar rats weighing 145 +/- 9 g which were subjected to pinealectomy or sham operation. In half of the animals from each group MEL (Sigma, USA) in a dose of 50 mg/100 g b.w. was administered intraperitonealy (daily between 17.00 and 18.00 h for a 4-week period). Material for studies (blood and urine) was collected every 3 hours during a day. Hormones, PICP and ICTP concentrations were determined with the use of RIA methods. whereas ALP, HYP and Ca values - spectrophotormetrically.

RESULTS

The study has shown that pinealectomy had an inducing, while exogenous MEL a suppressing effect upon the level of investigated biochemical markers of bone metabolism. Furthermore, substantial changes in the values of amplitude and phase of their circadian oscillations were shown. Distinct, dependent on the time of day disturbances in circadian fluctuations of PICP, ICTP, HYP and Ca showing generally negative correlation with changes in endogenous MEL concentrations and positive with IGF-I and corticosterone (B) levels were found. In addition, changes in circadian oscillations of ALP and PICP correlated negatively with daily oscillations of calciotropic hormones and B. However, ICTP, HYP and Ca concentrations correlated positively with circadian fluctuations of B and FT3 (the latter only in sham operated rats receiving MEL).

CONCLUSIONS

This study showed that both pinealectomy and long-term MEL administration influence the circadian rhythm of bone metabolism and that an important role in the mechanism of this dependence is played by the changes of endogenous MEL levels. Secondary changes in circadian oscillations of calciotropic hormones, IGF-I and corticosterone concentrations, caused by pinealectomy and long-term MEL administration result in altered bone metabolism rhythm.

Short fasting dramatically decreases rat duodenal secretory responsiveness to orexin A but not to VIP or melatonin

Orexins are involved in the central nervous control of appetite and behavior, and in addition, they are present in endocrine cells and/or neurons in the intestine. The role of these peptides in peripheral regulation of intestinal secretion has not been investigated. We thus compared the effects of orexin A and some established secretagogues on duodenal HCO3- secretion in fed rats with effects in rats exposed to short (overnight) food deprivation. Rats were anesthetized with thiobarbiturate, a 12-mm segment of proximal duodenum with intact blood supply was cannulated in situ, and the alkaline secretion was titrated by pH stat. Secretagogues were supplied specifically to the duodenum by close intra-arterial infusion. Orexin A (60-600 pmol x kg(-1) x h(-1)) caused marked and dose-dependent stimulation of the duodenal secretion in fed animals but did not affect secretion in overnight food-deprived animals. Similarly, short fasting caused a 100-fold increase in the amount of the muscarinic agonist bethanechol (from 50 to 5,000 nmol x kg(-1) x h(-1)) required for stimulation of the secretion. In contrast, the secretory responses to VIP (50-1,000 pmol x kg(-1) x h(-1)) and melatonin (20-200 nmol x kg(-1) x h(-1)) were not affected. The appetite-regulating peptide orexin A is thus a stimulant of intestinal secretion, but the response to this peptide as well as the muscarinic agonist bethanechol is markedly dependent on previous intake of food. Overnight fasting is a standard experimental procedure in studies of gastrointestinal function and pathophysiology in humans and animals. Studies made on neuroendocrine control of intestinal secretion may require reevaluation with respect to feeding status.