Melatonin: a clinical perspective

Sex and stress hormone dysregulation as clinical manifestations of hypothalamic function in migraine disorder: A meta-analysis

Migraine is a leading cause of disability in young adults. It occurs more frequently in females, often comorbidly with stress disorders, suggesting an association with hypothalamic sex and stress hormonal function and a likely interaction with autonomic nervous system activation. Thus, this study aimed to meta-analyse current literature pertaining to female and male sex hormones (estrogen, progesterone and testosterone concentration), hypothalamic-pituitary-adrenal axis (HPA axis) cortisol responses and heart rate variability (HRV) in migraineurs and controls aged 13-65 years. A systematic search of MEDLINE, Embase, PsycINFO, PubMed, CINAHL and Web of Science databases on 29/08/2022 identified 29 studies for meta-analysis (encompassing 719 migraineur and 592 control participants) that met inclusion and NHLBI risk of bias criteria. Results demonstrated that estrogen concentrations of female migraineurs were reduced (g = -.60, 95% CI [-.91, -.29], p < .001) in the luteal phase of the menstrual cycle, compared to controls. No differences were found in progesterone levels overall in female migraineurs, nor in testosterone levels in male migraineurs compared to controls. Further, early diurnal cortisol concentrations were elevated (g = .32, 95% CI [.00, .63], p = .036) in female and male migraineurs compared to controls, though no differences were found in HRV of female or male migraineurs compared to controls. These findings of dysregulation of estrogen in females and cortisol dysregulation in female and male migraineurs indicate perturbed hypothalamic function and highlight the association of migraine with stress and the need for further rigorous investigation of hypothalamic neuroendocrine functions in migraineurs of both sexes.

Diagnosis, pathophysiology, and management of cluster headache

Cluster headache is a trigeminal autonomic cephalalgia characterised by extremely painful, strictly unilateral, short-lasting headache attacks accompanied by ipsilateral autonomic symptoms or the sense of restlessness and agitation, or both. The severity of the disorder has major effects on the patient's quality of life and, in some cases, might lead to suicidal ideation. Cluster headache is now thought to involve a synchronised abnormal activity in the hypothalamus, the trigeminovascular system, and the autonomic nervous system. The hypothalamus appears to play a fundamental role in the generation of a permissive state that allows the initiation of an episode, whereas the attacks are likely to require the involvement of the peripheral nervous system. Triptans are the most effective drugs to treat an acute cluster headache attack. Monoclonal antibodies against calcitonin gene-related peptide, a crucial neurotransmitter of the trigeminal system, are under investigation for the preventive treatment of cluster headache. These studies will increase our understanding of the disorder and perhaps reveal other therapeutic targets.

Melatonin: Protection against age-related cardiac pathology

Aging is a complex and progressive process that involves physiological and metabolic deterioration in every organ and system. Cardiovascular diseases are one of the most common causes of mortality and morbidity among elderly subjects worldwide. Most age-related cardiovascular disorders can be influenced by modifiable behaviours such as a healthy diet rich in fruit and vegetables, avoidance of smoking, increased physical activity and reduced stress. The role of diet in prevention of various disorders is a well-established factor, which has an even more important role in the geriatric population. Melatonin, an indoleamine with multiple actions including antioxidant properties, has been identified in a very large number of plant species, including edible plant products and medical herbs. Among products where melatonin has been identified include wine, olive oil, tomato, beer, and others. Interestingly, consumed melatonin in plant foods or melatonin supplementation may promote health benefits by virtue of its multiple properties and it may counteract pathological conditions also related to cardiovascular disorders, carcinogenesis, neurological diseases and aging. In the present review, we summarized melatonin effects against age-related cardiac alterations and abnormalities with a special focus on heart ischemia/reperfusion (IR) injury and myocardial infarction.

Melatonin secretion is impaired in women with preeclampsia and an abnormal circadian blood pressure rhythm

Non-dipping circadian blood pressure (BP) is a common finding in preeclampsia, accompanied by adverse outcomes. Melatonin plays pivotal role in biological circadian rhythms. This study investigated the relationship between melatonin secretion and circadian BP rhythm in preeclampsia. Cases were women with preeclampsia treated between January 2006 and June 2007 in the University Hospital of Larissa. Volunteers with normal pregnancy, matched for chronological and gestational age, served as controls. Twenty-four hour ambulatory BP monitoring was applied. Serum melatonin and urine 6-sulfatoxymelatonin levels were determined in day and night time samples by enzyme-linked immunoassays. Measurements were repeated 2 months after delivery. Thirty-one women with preeclampsia and 20 controls were included. Twenty-one of the 31 women with preeclampsia were non-dippers. Compared to normal pregnancy, in preeclampsia there were significantly lower night time melatonin (48.4 ± 24.7 vs. 85.4 ± 26.9 pg/mL, p<0.001) levels. Adjustment for circadian BP rhythm status ascribed this finding exclusively to non-dippers (p<0.01). Two months after delivery, in 11 of the 21 non-dippers both circadian BP and melatonin secretion rhythm reappeared. In contrast, in cases with retained non-dipping status (n=10) melatonin secretion rhythm remained impaired: daytime versus night time melatonin (33.5 ± 13.0 vs. 28.0 ± 13.8 pg/mL, p=0.386). Urinary 6-sulfatoxymelatonin levels were, overall, similar to serum melatonin. Circadian BP and melatonin secretion rhythm follow parallel course in preeclampsia, both during pregnancy and, at least 2 months after delivery. Our findings may be not sufficient to implicate a putative therapeutic effect of melatonin, however, they clearly emphasize that its involvement in the pathogenesis of a non-dipping BP in preeclampsia needs intensive further investigation.

Bench to cribside: the path for developing a neuroprotectant

The consequences of perinatal brain injury include immeasurable anguish for families and substantial ongoing costs for care and support of effected children. Factors associated with perinatal brain injury in the preterm infant include inflammation and infection, and with increasing gestational age, a higher proportion is related to hypoxic-ischemic events, such as stroke and placental abruption. Over the past decade, we have acquired new insights in the mechanisms underpinning injury and many new tools to monitor outcome in perinatal brain injury in our experimental models. By embracing these new technologies, we can expedite the screening of novel therapies. This is critical as despite enormous efforts of the research community, hypothermia is the only viable neurotherapeutic, and this procedure is limited to term birth and postcardiac arrest hypoxic-ischemic events. Importantly, experimental and preliminary data in humans also indicate a considerable therapeutic potential for melatonin against perinatal brain injury. However, even if this suggested potential is proven, the complexity of the human condition means we are likely to need additional neuroprotective and regenerative strategies. Thus, within this review, we will outline what we consider the key stages of preclinical testing and development for a neuroprotectant or regenerative neurotherapy for perinatal brain injury. We will also highlight examples of novel small animal physiological and behavioral testing that gives small animal preclinical models greater clinical relevance. We hope these new tools and an integrated bench to cribside strategic plan will facilitate the fulfillment of our overarching goal, improving the long-term brain health and quality of life for infants suffering perinatal brain injury.

Light exposure at night, sleep duration and sex hormone levels in pregnant Japanese women

The association between light exposure at night and sex hormone levels in utero has scarcely reported. We assessed the associations between sleep duration or being awake in the late evening hours, which can be as indicator of light exposure at night, and the maternal and umbilical blood hormone levels during pregnancy and at delivery among Japanese women. The data for 236 women and their newborns who visited a maternal clinic in Gifu, Japan, between May 2000 and October 2001 were analyzed. Maternal blood samples were obtained at approximately the 10th weeks, 29th weeks of gestation, and at delivery. Umbilical cord artery blood was immediately drawn after birth. Information for sleep during pregnancy was obtained by a self-administered questionnaire. The levels of estradiol and testosterone were measured using radioimmunoassay. Maternal serum testosterone level in the 10th week was higher among those who were awake at or after 1:00 a.m. than among those who were asleep at that time (P = 0.032). Maternal estradiol level in the 29th week was inversely associated with sleep duration on weekends (P = 0.043). Umbilical testosterone level at delivery inversely correlated with sleep duration on weekdays (P = 0.030). These associations were somewhat stronger among mothers with female offspring than those with male offspring. These results suggested that exposure to light at night might increase sex hormone levels during pregnancy.

Serum melatonin levels in adolescent idiopathic scoliosis prediction and prevention for curve progression--a prospective study

The correlation of serum melatonin levels and curve progression in adolescent idiopathic scoliosis, and the effects of melatonin therapy in scoliotic patients with reduced levels of endogenous melatonin were studied in 40 adolescent patients with moderate to severe idiopathic scoliosis. Of the scoliotic subjects, 28 had stable scoliosis and 12 had progressive scoliosis. Normal melatonin levels were derived from 25 age-matched control patients. Serum melatonin levels were monitored yearly in scoloiotic patients for a period ranging from 3 to 6 yr, revealing a diurnal pattern with low values during the day and high at night. Scoliotic patients with normal levels were not treated or were treated with a brace, and all but two patients with low endogenous melatonin were treated with oral supplements of the indole. Of the 22 patients with a normal melatonin level, 16 had stable scoliosis and six had progressive scoliosis. Of the 16 patients treated for a low melatonin level, 12 had stable scoliosis and four had a progressive course. The two untreated cases had a progressive course. Of the 12 patients who had progressive scoliosis, nine had >35 degrees of curve at initial examination. These findings suggest that melatonin deficiency plays a role in the prognosis of idiopathic scoliosis. Therefore, melatonin supplements may prevent the progression of scoliosis, especially in mild cases with less than a 35 degrees curve.

Light exposure at night, urinary 6-sulfatoxymelatonin, and serum estrogens and androgens in postmenopausal Japanese women

It has been hypothesized that exposure to light at night increases the risk of breast cancer by suppressing the normal nocturnal increase in melatonin production and release, thereby resulting in increased levels of circulating estrogen. We assessed associations among concentrations of serum estrogen and androgen and the principal metabolite of melatonin in urine, 6-sulfatoxymelatonin, and exposure to light at night based on information regarding the sleeping habits and history of graveyard-shift work of 206 postmenopausal Japanese women. Serum estradiol level was significantly higher in women who were not asleep at or after 1:00 a.m. (the approximate time of the melatonin peak) than those who were asleep after controlling for covariates. Significantly increased estrone levels were observed in women who had worked graveyard shift. Serum testosterone and DHEA sulfate were unrelated to sleeping habits and history of graveyard-shift work. Urinary 6-sulfatoxymelatonin was lower in women who were not asleep at or after 1:00 a.m. on weekends than those who were asleep at this time, but the difference was of borderline significance (P = 0.08). There was no significant association between urinary 6-sulfatoxymelatonin and any serum hormone levels. These data suggest that exposure to light at night has implications for the risk of breast cancer in postmenopausal women. However, the potential role of melatonin as an intervening factor between light exposure at night and the serum concentrations of estrogen was equivocal.

Melatonin prevents learning disorders in brain-lesioned newborn mice

Perinatal brain injuries often result in irreversible learning disabilities, which manifest in early childhood. These injuries are chiefly ascribable to marked susceptibility of the immature brain to glutamate-induced excitotoxicity. No treatments are available. One well-characterized model of perinatal brain injuries consists in injecting the glutamate analog ibotenate into the brain of 5-day-old mice. The resulting excitotoxic lesions resemble the hypoxic-ischemic gray-matter lesions seen in full-term and near-term newborns, as well as the white-matter lesions of preterm newborns. We previously reported that these lesions disrupted odor preference conditioning in newborn mice. The aim of this study was to assess the effectiveness of the neuroprotector melatonin in preventing learning disabilities in newborn mice with ibotenate-induced brain injury. In postnatal day (P) 6-P7 pups, we tested psychomotor reflexes, spontaneous preference for maternal odors as an index of memory, ultrasonic vocalization responses to stroking as an index of sensitivity to tactile stimuli, and conditioned preference for an odor previously paired with stroking as an index of learning abilities. Without melatonin, conditioning was abolished, whereas spontaneous odor preference, psychomotor reflexes, and sensitivity to tactile stimuli were normal. Thus, abolition of conditioning was not associated with sensorimotor impairments. Histological analysis confirmed the efficacy of melatonin in reducing white-matter lesions induced by ibotenate. Furthermore, treatment with melatonin protected the ability to develop conditioning. Thus, melatonin, which easily crosses the blood-brain barrier and has been proven safe in children, may be effective in preventing learning disabilities caused by perinatal brain injuries in human preterm infants.

Growth factors and plasticity

Neuroprotective strategies can prevent lesions from getting worse but agents that have neurotrophic properties can also affect repair in a developing brain. Although prevention and treatment in the early stages of brain lesions are desirable, delayed cell death or improved post-lesion plasticity are the only realistic targets in many cases. Several trophic factors can limit delayed cell death in animal models of perinatal brain damage. In addition, melatonin and brain-derived neurotrophic factor have been shown to promote post-lesion plasticity following neonatal excitotoxic white-matter damage in newborn mice. Despite these promising results, additional preclinical data are required for most of the trophic factors that have been tested, although some candidate drugs, e.g. melatonin or erythropoietin, might reach clinical trials in the near future.

Melatonin Administration Acutely Decreases the Diffusing Capacity of Carbon Monoxide in Human Lungs

BACKGROUND

Most physiological measurements of the pulmonary diffusing capacity use carbon monoxide (CO) as a tracer gas. Similar to CO, melatonin binds the hemoglobin in the blood.

OBJECTIVE

The present study was designed to assess the effect of exogenous melatonin administration on pulmonary functions including diffusing capacity for carbon monoxide (DL(CO)) in healthy subjects.

METHODS

The study was performed in a randomized, double-blind, placebo-controlled manner. DL(CO) was measured in 22 healthy male volunteers (age 18-25 years) who were randomized to melatonin (n = 11) and placebo administration (n = 11). At baseline, DL(CO), alveolar volume (V(A)) and other spirometric parameters such as forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC), peak expiratory flow (PEF) and maximal voluntary ventilation (MVV) were measured. DL(CO) was then corrected for the hemoglobin concentration. Measurements were repeated in a double-blind fashion 60 min after the administration of melatonin (1 mg) or placebo.

RESULTS

DL(CO) was significantly decreased (39.31 +/- 4.75 vs. 34.82 +/- 6.18 ml/min/mm Hg) 60 min after the melatonin administration (p = 0.01), while FEV(1), FVC, FEV(1)/FVC, PEF and MVV values did not demonstrate significant differences. Placebo administration did not result in significant alteration in any of these parameters.

CONCLUSIONS

In healthy subjects, oral administration of melatonin acutely influences the DL(CO) without affecting other pulmonary function test results. We conclude that melatonin may have a reducing effect on the DL(CO) in the lungs.

An enigmatic eye: the histology of the tuatara pineal complex

AIM

To examine the histology of the tuatara pineal complex and to compare findings with those of Dendy. Some reptiles have an anatomically sophisticated pineal complex with a median pineal eye, a paraphysis and a pineal sac. In comparison, the human pineal gland is simple and homogenous and thought to be a phylogenetic relic. It is now considered a neuroendocrine gland the function of which is still not fully understood. Its simple anatomical structure is in contrast to its biochemical complexity; its secretions (the most studied being melatonin) modifying the function of the adeno- and neurohypophysis, thyroid and parathyroids, adrenal cortex and medulla, endocrine pancreas and the gonads.

METHODS

Histological sections of the brain of a neonatal tuatara were studied by light microscopy.

RESULTS

The histological findings of the pineal eye demonstrated a cornea-like structure, rudimentary lens and simple retina. The adjacent paraphysis was a large, multisaccular organ and the pineal sac a very large saccular organ with a poorly differentiated retina.

CONCLUSION

The pineal eye of the tuatara has a remarkably eye-like structure with photoreceptors that in other reptiles have been shown to exhibit photoreceptive capabilities. The paraphysis appeared to have a secretory function that is as yet undetermined, while the pineal sac had the appearance of a poorly differentiated retina. Thus it appears that the complex biochemistry of the human pineal gland is reflected in the complex anatomical structure of this primitive reptile.

Strategies leading to MT2 selective melatonin receptor antagonists

Studies of the physiological actions of melatonin have been hindered by the lack of specific, potent and subtype selective agonists and antagonists. This paper reviews our progress in developing subtype selective melatonin antagonists. Evidence is presented suggesting the structural features conferring MT2 selective antagonism.

Decreased nocturnal synthesis of melatonin in patients with coronary artery disease

In human beings, cardiovascular activity has a distinct circadian variation: Heart rate, blood pressure, and vascular tone decrease at night. Nocturnal cardiovascular blunting is at least partially linked to the autonomic activity and increased risk of cardiac and cerebral events. To assess whether decreased nocturnal melatonin synthesis and secretion in coronary artery disease (CAD), we investigated nocturnal secretion pattern of melatonin in patients with CAD and healthy subjects. The present study performed in 16 patients with angiographically documented CAD (aged 46-71 years) and in nine healthy controls (aged 36-66 years). Blood samples were collected every 2 h between 22:00 and 08:00 h. Melatonin levels were measured with a commercially available radioimmunoassay kit. We found large interindividual variation in the pattern of melatonin secretion in both groups. Patients with CAD secreted less nocturnal melatonin at 02:00, 04:00 and 08:00 h than control subjects (P=0.014, P=0.04 and P=0.025, respectively). Peak and Delta melatonin (peak-lowest melatonin) were found lower in patients with CAD (48.6 [19.1-75.4] vs. 131.4 [67.8-137.2] pg/ml, P=0.006 and 43 [10.5-68.5] vs. 107.6 [55.7-113.1] pg/ml, P=0.002, respectively). Peak time of melatonin secretion was observed earlier in patients with CAD (02:00 h [23:00-02:00 h] vs. 03:45 h [02:00-05:00 h], P=0.04). Our study provides useful and preliminary information about decreased nocturnal melatonin synthesis and release in patients with CAD might help physicians in managing these patients.

Impaired nocturnal synthesis of melatonin in patients with cardiac syndrome X

We investigated nocturnal secretion pattern of melatonin in patients with cardiac syndrome X and healthy subjects. The present study performed in five patients with cardiac syndrome X and in nine healthy controls. Blood samples from all subjects were collected every 2 h intervals between 22:00 and 08:00 h. Melatonin levels were measured with a radioimmunoassay kit. Patients with cardiac syndrome X secreted less nocturnal melatonin at 02:00 h than control subjects (P=0.04). Peak and Delta melatonin (peak-lowest melatonin) were found lower in patients with cardiac syndrome X (P=0.039 and P=0.028, respectively). In conclusion patients with cardiac syndrome X show a markedly decreased nocturnal melatonin synthesis. Our study provides useful information about melatonin synthesis and release in patients with cardiac syndrome X might help physicians in managing these patients.

Cluster headache: evidence for a disorder of circadian rhythm and hypothalamic function

This article reviews the literature for evidence of a disorder of circadian rhythm and hypothalamic function in cluster headache. Cluster headache exhibits diurnal and seasonal rhythmicity. While cluster headache has traditionally been thought of as a vascular headache disorder, its periodicity suggests involvement of the suprachiasmatic nucleus of the hypothalamus, the biological clock. Normal circadian function and seasonal changes occurring in the suprachiasmatic nucleus and pineal gland are correlated to the clinical features and abnormalities of circadian rhythm seen in cluster headache. Abnormalities in the secretion of melatonin and cortisol in patients with cluster headache, neuroimaging of cluster headache attacks, and the use of melatonin as preventative therapy in cluster headache are discussed in this review. While the majority of studies exploring the relationship between circadian rhythms and cluster headache are not new, we have entered a new diagnostic and therapeutic era in primary headache disorders. The time has come to use the evidence for a disorder of circadian rhythm in cluster headache to further development of chronobiotics in the treatment of this disorder.

Melatoninergic neuroprotection of the murine periventricular white matter against neonatal excitotoxic challenge

Periventricular leukomalacia is one of the main causes of cerebral palsy. Perinatal white matter lesions associated with cerebral palsy appears to involve glutamate excitotoxicity and excess free radical production. When injected intracerebrally into newborn mice, the glutamatergic analog ibotenate induces white matter cysts mimicking human periventricular leukomalacia. Melatonin acts on specific receptors. It also exhibits intrinsic free radical scavenging properties. The goal of the present study is to determine whether melatonin can protect against excitotoxic lesions induced by ibotenate in newborn mice. Mice that received intraperitoneal melatonin had an 82% reduction in size of ibotenate-induced white matter cysts when compared with controls. Although melatonin did not prevent the initial appearance of white matter lesions, it did promote secondary lesion repair. Axonal markers supported the hypothesis that melatonin induced axonal regrowth or sprouting. The protective effects of melatonin were suppressed by coadministration of luzindole, a melatonin receptor antagonist. Forskolin, an adenylate cyclase activator, prevented the protective effects of melatonin; inhibitors of protein kinase C and mitogen-associated protein kinase had no detectable effect. Melatonin and derivatives that block cAMP production through activation of melatonin receptors could represent new avenues for treating human periventricular leukomalacia.

Hypothalamic involvement in chronic migraine

OBJECTIVES

Chronic migraine (CM), previously called transformed migraine, is a frequent headache disorder that affects 2%-3% of the general population. Analgesic overuse, insomnia, depression, and anxiety are disorders that are often comorbid with CM. Hypothalamic dysfunction has been implicated in its pathogenesis, but it has never been studied in patients with CM. The aim was to analyze hypothalamic involvement in CM by measurement of melatonin, prolactin, growth hormone, and cortisol nocturnal secretion.

METHODS

A total of 338 blood samples (13/patient) from 17 patients with CM and nine age and sex matched healthy volunteers were taken. Melatonin, prolactin, growth hormone, and cortisol concentrations were determined every hour for 12 hours. The presence of comorbid disorders was also evaluated.

RESULTS

An abnormal pattern of hypothalamic hormonal secretion was found in CM. This included: (1) a decreased nocturnal prolactin peak, (2) increased cortisol concentrations, (3) a delayed nocturnal melatonin peak in patients with CM, and (4) lower melatonin concentrations in patients with CM with insomnia. Growth hormone secretion did not differ from controls.

CONCLUSION

These results support hypothalamic involvement in CM, shown by a chronobiologic dysregulation, and a possible hyperdopaminergic state in patients with CM. Insomnia might be an important variable in the study findings.

2-N-acylaminoalkylindoles: design and quantitative structure-activity relationship studies leading to MT2-selective melatonin antagonists

Several indole analogues of melatonin (MLT) were obtained by moving the MLT side chain from C(3) to C(2) of the indole ring. Binding and in vitro functional assays were performed on cloned human MT1 and MT2 receptors, stably transfected in NIH3T3 cells. Quantitative structure-activity relationship studies showed that 4-methoxy-2-(N-acylaminomethyl)indoles, with a benzyl group in position 1, were selective MT2 antagonists and, in particular, N-[(1-p-chlorobenzyl-4-methoxy-1H-indol-2-yl)methyl]propanamide (12) behaved as a pure antagonist at MT1 and MT2 receptors, with a 148-fold selectivity for MT2. We present a topographical model that suggests a lipophilic group, located out of the plane of the indole ring of MLT, as the key feature of the MT2 selective antagonists.

Melatonin secretion occurs at a constant rate in both young and older men and women

The magnitude and duration of melatonin (MLT) secretion were measured over a period of 25 h with pharmacokinetic studies employing administration of D(7) MLT at midday and at midnight in two separate studies and two groups of subjects, 12 young and 11 older men and women. Plasma levels of endogenous MLT and D(7) MLT were quantified separately by use of a specific and sensitive method (gas chromatography-mass spectrometry) previously developed in our laboratory, enabling us to measure endogenous and exogenous MLT levels down to 0.5 pg/ml in plasma. In the two groups of subjects, MLT secretion occurred only at night: onset time of secretion was from 1915 to 2205 (Greenwich mean time), and offset was from 0305 to 0545. No MLT peak was observed in individual nocturnal MLT profiles that were similar to curves obtained for a rate-constant infusion. Modelization demonstrated the superimposition of observed data and simulated curves. MLT concentrations decreasing from the offset of secretion might correspond to the elimination of MLT present in the body at the end of nocturnal secretion. By use of the MLT clearance given by pharmacokinetics, the amount of secreted MLT was found to be 35.7 and 21.6 microg for men and women, respectively, and the rate of secretion was 4.6 and 2.8 microg/h, respectively. No significant gender difference was observed for these two parameters when normalized to body weight. No significant gender difference was observed for onset times of secretion or duration of secretion (7.6-8.6 h) within the two groups, or between young and older subjects.

Psychiatric aspects of jet lag: review and hypothesis

Jet lag is a travel-induced circadian rhythm phenomenon that afflicts healthy individuals following long- distance flights through several time zones. The typical jet-lag manifestations - insomnia during local sleep time, day fatigue, reduced concentration, irritability, and exhaustion with mild depression - are attributed to transient desynchronization in the circadian rhythm until the internal biological clock is rephased to the new environmental conditions. There is strong evidence relating affective disorders with circadian rhythm abnormalities. Less convincing suggestions relate jet lag to psychosis. It can be hypothesized that in predisposed individuals jet lag may play a role in triggering exacerbation or even de novo affective disorders. Furthermore, we propose the possibility that psychosis and even schizophrenia can be elicited by jet lag. This outlook gains its support from case studies and some common underlying phase-advanced biological denominators involved in both jet lag sufferers and psychotic patients.

Melatonin for the treatment of handicapped children with severe sleep disorders

Sleep disorders are common in children with mental retardation and neurologic disorders. Melatonin, a recently developed natural compound, has been used successfully in sleep disorders. I report my experience with melatonin in an open, prospective trial to treat circadian rhythm sleep disorder in handicapped children. The sleep disorder had been present for at least 6 months and had not responded to at least one hypnotic drug. The therapeutic response was recorded according to the average number of hours asleep per 24 hours, average number of awakening per night, average number of nights with delayed sleep onset, and average number of nights with early morning arousals. Ten consecutive children (four males, six females; age range = 1-11 years, mean 5.4) were included. Nine children had documented mental retardation that was severe in six (67%). Most had epilepsy and visual impairment (70%). All children were monitored for 4-12 months (mean 7.5 months) after the initiation of 3-mg bedtime melatonin. Most (80%) had a dramatic response to melatonin. No side effects were reported. Melatonin is a well-tolerated, safe, relatively inexpensive, and effective drug, with minimal side effects, for the treatment of severe circadian rhythm sleep disorder in handicapped children. Wider use of this drug is recommended.

The therapeutics of melatonin: a paediatric perspective

The production of melatonin by the pineal gland and its functions are considered, and then its possible uses in the treatment of children. Institutionalized children, and those with severe learning disorders, often have irregular sleep-wake patterns, and there is evidence that melatonin can result in improvement to the benefit of both the child and the carers. The affected children can become less irritable, calmer, happier, and content. Also they may socialize better and become more attentive, with an improvement in their cognitive abilities. Another group of children who are likely to suffer from disturbed sleep are those who are visually handicapped. Melatonin given in the evening can improve their sleep patterns, and often their performance. No important side-effects have been reported. It is generally accepted that if a child is liable to epileptic seizures sleep deprivation may well exacerbate them. There is some evidence from clinical trials that in that event melatonin can be helpful. There are many other problems in which it is claimed that treatment with melatonin is justifiable. These are mentioned, but further confirmatory studies are needed in most of them. There is no doubt that melatonin can effect the circadian system, and shift the sleep-wake cycle; and that there are situations in which this can be desirable.

Melatonin fails to protect against long-term MPTP-induced dopamine depletion in mouse striatum

Several laboratories recently have reported that melatonin may possess neuroprotective properties. The present paper presents the results of our studies on the long term in vivo neuroprotective effects of melatonin in a well-defined neurotoxicity model using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the C57BL/6 mouse. MPTP is bioactivated by brain monoamine oxidase B (MAO-B) to its neurotoxic pyridinium metabolite 1-methyl-4-phenylpyridinium (MPP(+)) which destroys dopaminergic nerve terminals leading to the depletion of neostriatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC). Our initial study compared striatal DA and DOPAC levels in MPTP-only-treated animals and animals treated with melatonin 30 min prior to and 3 times hourly post-MPTP. DA/DOPAC levels measured 7 days after MPTP were similar in both groups. A second study was designed to address the possibility that melatonin cleared from the brain prior to MPP(+). Animals, that had been administered the same regimen of melatonin as in the first study plus a fourth post-MPTP melatonin dose, were maintained on melatonin in drinking water until 5 days post-MPTP. Striatal DA/DOPAC levels of these melatonin-plus-MPTP treated animals also were the same as the MPTP-only-treated animals. In vitro studies confirmed that melatonin is not an inhibitor of MAO-B. These data demonstrate that melatonin does not have any significant protective effects against the long-term striatal DA and DOPAC depletion induced by MPTP in the C57BL/6 mouse.

Complementary and alternative medicines for Alzheimer's disease

The recent successes of large, multicenter clinical trials of acetylcholinesterase inhibitors for symptomatic treatment of Alzheimer's disease have spawned enthusiasm that this common and fatal neurologic disease is "treatable." A parallel explosion has occurred in the consumption of alternative medicines by the public seeking more effective, natural, or safer methods for treatment of dementia. Some of these medicines may, in fact, be biologically active in modulating the disease as well as producing side effects and interactions with accepted pharmaceuticals. This review brings to focus the scientific evidence presently available regarding such agents.

Melatonin biosynthesis: the structure of serotonin N-acetyltransferase at 2.5 A resolution suggests a catalytic mechanism

Conversion of serotonin to N-acetylserotonin, the precursor of the circadian neurohormone melatonin, is catalyzed by serotonin N-acetyltransferase (AANAT) in a reaction requiring acetyl coenzyme A (AcCoA). AANAT is a globular protein consisting of an eight-stranded beta sheet flanked by five alpha helices; a conserved motif in the center of the beta sheet forms the cofactor binding site. Three polypeptide loops converge above the AcCoA binding site, creating a hydrophobic funnel leading toward the cofactor and serotonin binding sites in the protein interior. Two conserved histidines not found in other NATs are located at the bottom of the funnel in the active site, suggesting a catalytic mechanism for acetylation involving imidazole groups acting as general acid/base catalysts.