Effect of melatonin on jet lag after long haul flights

Does melatonin administration reduce the incidence of postoperative delirium in adults? Systematic review and meta-analysis

Postoperative delirium (POD) is common. It is associated with increased morbidity and mortality. Many cases may be preventable and melatonin offers promise as a preventative agent.

OBJECTIVE

This systematic review provides an up-to-date synthesis of the evidence on the effect of melatonin in preventing POD.

DESIGN

A systematic search of randomised controlled trials of melatonin in POD was run across multiple databases (EMBASE, MEDLINE, CINAHL, PsycINFO) and a clinical trials registry (ClinicalTrials.org) (1 January 1990 to 5 April 2022). Studies examining the effects of melatonin on POD incidence in adults are included. Risk of bias was assessed using the Cochrane risk of bias 2 tool.

OUTCOME MEASURES

The primary outcome is POD incidence. Secondary outcomes are POD duration and length of hospital stay. Data synthesis was undertaken using a random-effects meta-analysis and presented using forest plots. A summary of methodology and outcome measures in included studies is also presented.

RESULTS

Eleven studies, with 1244 patients from a range of surgical specialties were included. Seven studies used melatonin, in variable doses, and four used ramelteon. Eight different diagnostic tools were used to diagnose POD. Time points for assessment also varied. Six studies were assessed as low risk of bias and five as some concern. The combined OR of developing POD in the melatonin groups versus control was 0.41 (95% CI 0.21 to 0.80, p=0.01).

CONCLUSION

This review found that melatonin may reduce the incidence of POD in adults undergoing surgery. However, included studies displayed inconsistency in their methodology and outcome reporting. Further work to determine the optimum regime for melatonin administration, along with consensus of how best to evaluate results, would be beneficial.

PROSPERO REGISTRATION NUMBER

CRD42021285019.

Travel across time zones and the implications for human performance post pandemic: Insights from elite sport

Notwithstanding technological innovation, the COVID-19 pandemic, and new communication tools, the need for travel is growing again and, in some travel segments, it is stronger than ever. Interestingly, the public health implications of traveling across time zones are still poorly understood and this is especially true for organizations that send their workers across the globe. Using data from 173 Olympic teams over 15 Olympic Games, we show that crossing multiple time zones has negative implications for human (sports) performance. More importantly, the results indicate that performance impairment is especially visible after flying east, with peak performance particularly impaired, leading to a "gold demotion effect" of gold medals to silver medals as a result. Given that Olympic sporting teams typically have dedicated medical staff and active mitigation strategies, these findings have important public health implications. For example, organizations are demanding their workers to be on "top of their game" while traveling, without providing them with the support and tools to do so. The implications for public health management and human resource management are discussed.

Melatonin for the prevention of postoperative delirium in older adults: a protocol for a systematic review and meta-analysis

INTRODUCTION

Postoperative delirium (POD) is a major cause of morbidity, particularly in elderly patients. Melatonin has been suggested as a low-risk pharmacological intervention to help prevent POD. A previous systematic review found limited high-quality evidence to support the use of melatonin in the prevention of POD. Several further randomised studies have since been published. This systematic review aims to synthesise the evidence from randomised controlled trials (RCTs) examining the effect of melatonin on the prevention of POD in older adults.

METHODS AND ANALYSIS

A systematic search of RCTs of melatonin (any dose and formulation) in POD will be run across Embase, Medline, CINAHL and PsychInfo. RCTs published from January 1990 until the end of February 2022 and reporting outcomes for melatonin use to prevent POD in patients will be included. Screening of search results and data extraction from included articles will be performed by two independent reviewers. The primary outcome will be incidence of POD in older adults undergoing surgery. Secondary outcomes are delirium duration and length of hospital stay. The review will also describe the dosage, timing and administration regimes of melatonin therapy and as well as the scales and definitions used to describe POD. A registry review of ongoing trials will be also be performed. For the meta-analysis, data will be pooled using a random effects model to generate a forest plot and obtain an odds ratio (OR) for the incidence of POD. Results will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

ETHICS AND DISSEMINATION

No ethical approval is required. This review will be disseminated via peer-reviewed manuscript and conferences. The results will be used as the basis of work to optimise this intervention for future trials in surgical populations.

PROSPERO REGISTRATION NUMBER

This review is registered with PROSPERO (CRD42021285019).

Is Melatonin the "Next Vitamin D"?: A Review of Emerging Science, Clinical Uses, Safety, and Dietary Supplements

Melatonin has become a popular dietary supplement, most known as a chronobiotic, and for establishing healthy sleep. Research over the last decade into cancer, Alzheimer's disease, multiple sclerosis, fertility, PCOS, and many other conditions, combined with the COVID-19 pandemic, has led to greater awareness of melatonin because of its ability to act as a potent antioxidant, immune-active agent, and mitochondrial regulator. There are distinct similarities between melatonin and vitamin D in the depth and breadth of their impact on health. Both act as hormones, affect multiple systems through their immune-modulating, anti-inflammatory functions, are found in the skin, and are responsive to sunlight and darkness. In fact, there may be similarities between the widespread concern about vitamin D deficiency as a "sunlight deficiency" and reduced melatonin secretion as a result of "darkness deficiency" from overexposure to artificial blue light. The trend toward greater use of melatonin supplements has resulted in concern about its safety, especially higher doses, long-term use, and application in certain populations (e.g., children). This review aims to evaluate the recent data on melatonin's mechanisms, its clinical uses beyond sleep, safety concerns, and a thorough summary of therapeutic considerations concerning dietary supplementation, including the different formats available (animal, synthetic, and phytomelatonin), dosing, timing, contraindications, and nutrient combinations.

Melatonin, an endogenous hormone, modulates Th17 cells via the reactive-oxygen species/TXNIP/HIF-1α axis to alleviate autoimmune uveitis

Background

Melatonin, an indoleamine produced by the pineal gland, plays a pivotal role in maintaining circadian rhythm homeostasis. Recently, the strong antioxidant and anti-inflammatory properties of melatonin have attracted attention of researchers. We evaluated the therapeutic efficacy of melatonin in experimental autoimmune uveitis (EAU), which is a representative animal model of human autoimmune uveitis.

Methods

EAU was induced in mice via immunization with the peptide interphotoreceptor retinoid binding protein 1–20 (IRBP_1–20). Melatonin was then administered via intraperitoneal injection to induce protection against EAU. With EAU induction for 14 days, clinical and histopathological scores were graded to evaluate the disease progression. T lymphocytes accumulation and the expression of inflammatory cytokines in the retinas were assessed via flow cytometry and RT-PCR, respectively. T helper 1 (Th1), T helper 17 (Th17), and regulatory T (Treg) cells were detected via flow cytometry for both in vivo and in vitro experiments. Reactive-oxygen species (ROS) from CD4 + T cells was tested via flow cytometry. The expression of thioredoxin-interacting protein (TXNIP) and hypoxia-inducible factor 1 alpha (HIF-1α) proteins were quantified via western blot.

Results

Melatonin treatment resulted in notable attenuation of ocular inflammation in EAU mice, evidenced by decreasing optic disc edema, few signs of retinal vasculitis, and minimal retinal and choroidal infiltrates. Mechanistic studies revealed that melatonin restricted the proliferation of peripheral Th1 and Th17 cells by suppressing their transcription factors and potentiated Treg cells. In vitro studies corroborated that melatonin restrained the polarization of retina-specific T cells towards Th17 and Th1 cells in addition to enhancing the proportion of Treg cells. Pretreatment of retina-specific T cells with melatonin failed to induce EAU in naïve recipients. Furthermore, the ROS/ TXNIP/ HIF-1α pathway was shown to mediate the therapeutic effect of melatonin in EAU.

Conclusions

Melatonin regulates autoimmune T cells by restraining effector T cells and facilitating Treg generation, indicating that melatonin could be a hopeful treatment alternative for autoimmune uveitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02477-z.

Travelers' perceptions of jetlag and travel fatigue: A scoping review

Effective management strategies for jetlag have largely been studied and evaluated through the lens of circadian science and biological rhythms. Jetlag is mostly self-managed by the individual. The most effective strategies require individuals to make behavioral changes to carefully alter sleep-wake schedules and time light exposure. However, travelers' perceptions, including their experiences, beliefs about jetlag/travel fatigue, and management expectations remain unclear. Therefore, the aim of this scoping review was to systematically synthesize the literature to understand what is currently known about travelers' perceptions of jetlag and travel fatigue. A literature search was conducted through EMBASE, PsycINFO, PubMed and Scopus generating 1164 results (2 articles known to authors), which were screened against our inclusion criteria. Twenty-two studies including data from 3952 participants were evaluated for its study design and traveler-centered outcome measures across the domains of: 1) Traveler Health Beliefs and Knowledge about Jetlag and Travel Fatigue; 2) Experience of Jetlag and Travel Fatigue 3) Traveler Priorities; 4) Self-reported Management Strategies for Jetlag and Travel Fatigue; and 5) User Experiences of Management Strategies. Synthesis of results suggests a potential mismatch between researchers' focus on circadian misalignment and travelers' focus on air travel comfort. A better understanding of the beliefs, attitudes, knowledge, satisfaction, experiences, and expectations about jetlag and travel fatigue will better enable the development of interventions that align with traveler priorities.

Evaluating chronotypically tailored light therapy for breast cancer survivors: Preliminary findings on fatigue and disrupted sleep

More than one-third of cancer survivors experience significant residual symptoms after treatment completion. Fatigue and sleep disruption often co-occur and exacerbate each other. The purpose of this preliminary analysis was to examine the effect of a chronotypically tailored light therapy on fatigue and sleep disruption in female survivors 1-3 years post-completion of chemotherapy and/or radiation for stage I to III breast cancer. The data for this analysis were collected as part of an ongoing two-group randomized controlled trial (NCT03304587). Participants were randomized to receive either bright blue-green light (experimental) or dim red light (control). Light therapy was self-administered using a light visor cap at home. Both groups received 30-min daily light therapy for 14 consecutive days either between 19:00 and 20:00 h (for morning chronotypes) or within 30 min of waking in the morning (for evening chronotypes). Fatigue and sleep quality were self-reported using the Patient-Reported Outcomes Measurement Information System (PROMIS)-Fatigue, PROMIS-Sleep Disturbance, Pittsburgh Sleep Quality Index, and a daily log before (pre-test) and following the light intervention (post-test). Linear mixed model analysis or generalized estimating equations examined group difference overtime adjusting for pre-test scores. No between-group differences were found. However, after adjusting for the baseline fatigue, the experimental group reported significant decreases in fatigue (p < .001) and sleep disturbance (p = .024) overtime. The experimental group also reported significantly better subjective sleep quality after 14 d of light therapy (p = .017). Positive trends in sleep latency, sleep duration, night-time awakenings, and early morning awakenings were also observed. Unexpectedly, sleep disturbance significantly decreased in the control group (p = .030). Those who received dim light control reported significantly shorter sleep latency (p = .002), longer total sleep time (p = .042), and greater habitual sleep efficiency (p = .042). These findings suggest that bright light therapy significantly improved post-treatment fatigue and subjective sleep quality in breast cancer survivors. Although it remains to be confirmed, the findings additionally show unexpected benefits of dim light on sleep. Properly timed light exposure may optimize the therapeutic effect and can be the key for successful light therapy. How the administration timing coupled with wavelengths (short vs. long) and intensity of light affecting fatigue and disrupted sleep requires further investigation.

Bright light shows promise in improving sleep, depression, and quality of life in women with breast cancer during chemotherapy: findings of a pilot study

Sleep and fatigue-associated symptoms are prominent during chemotherapy. The purpose of this pilot study was to examine bright light effects on sleep disruption, fatigue, daytime sleepiness, depression, and quality of life (QOL) in women with stage I-III breast cancer undergoing chemotherapy. In this 2-group randomized controlled trial (NCT02658708), participants were randomized to receive either blue-green light of 12,000 lux (experimental) or dim red light of 5 lux (control). Light therapy was self-administered using a light visor cap at home. Both groups received 30-minute daily light therapy for 21 consecutive days following the 2nd cycle of chemotherapy. Sleep quality, fatigue, daytime sleepiness, depression, and QOL were self-reported, and nocturnal sleep was monitored by ambulatory polysomnography before the initiation of chemotherapy (baseline) and following the light intervention (posttest). Relative change was assessed at posttest controlling for pretest scores. At posttest, the experimental group self-reported significantly shorter sleep latency than controls (10 vs. 20 min, p = .045) consistent with polysomnography findings (14 vs. 63 min). Polysomnography also revealed longer total sleep time (467 vs. 315 min) and higher sleep efficiency (74% vs. 58%) in experimental vs. controls. Participants receiving bright light experienced a 30% relative decrease in depression, while there was a 24% increase in the controls. The experimental group reported substantially fewer increases in symptom intensity than controls (33% vs. 166%). These findings suggest that bright light likely improved sleep quality and depression and mitigated worsening intensity of symptoms during the first three cycles of chemotherapy. However, features of bright light, e.g., treatment duration, frequency, and timing in relation to chemotherapy treatment require further investigation.

Efficacy of Functional Foods, Beverages, and Supplements Claiming to Alleviate Air Travel Symptoms: Systematic Review and Meta-Analysis

Airline passengers experience a range of symptoms when travelling on long flights. This review evaluated the efficacy of functional foods, beverages, and supplements claiming to address the effects of air travel for healthy adults. Products were identified in a scoping review of electronic databases, search engines, and grey literature (March to August 2019). A systematic review of the efficacy of product ingredients was conducted using five electronic databases from inception to February 2021. Articles were screened, data extracted, and assessed for risk of bias by two researchers independently. Meta-analysis was performed. Of the 3842 studies identified, 23 met selection criteria: melatonin (n = 10), Pycnogenol (n = 4), various macronutrients (n = 2), caffeine (n = 2), Centella asiatica (n = 1), elderberry (n = 1), Echinacea (n = 1), fluid (n = 1), and Pinokinase (n = 1). Meta-analysis (random effects model) indicated melatonin reduced self-reported jetlag following eastbound (n = 5) and westbound (n = 4) flights: standard mean difference −0.76 (95% CI = −1.06 to −0.45, I2 0%, p < 0.00001) and −0.66 (95% CI = −1.07 to −0.26, I2 45%, p = 0.001), respectively. Pycnogenol also reduced edema scores (n = 3), standard mean −4.09 (95% CI = −6.44 to −1.74), I2 98%, p = 0.0006). Overall, 12 of 183 ingredients contained in 199 products had evidence to support claims.

Circadian Rhythm Sleep-Wake Disorders: a Contemporary Review of Neurobiology, Treatment, and Dysregulation in Neurodegenerative Disease

Circadian rhythms oscillate throughout a 24-h period and impact many physiological processes and aspects of daily life, including feeding behaviors, regulation of the sleep-wake cycle, and metabolic homeostasis. Misalignment between the endogenous biological clock and exogenous light-dark cycle can cause significant distress and dysfunction, and treatment aims for resynchronization with the external clock and environment. This article begins with a brief historical context of progress in the understanding of circadian rhythms, and then provides an overview of circadian neurobiology and the endogenous molecular clock. Various tools used in the diagnosis of circadian rhythm sleep-wake disorders, including sleep diaries and actigraphy monitoring, are then discussed, as are the therapeutic applications of strategically timed light therapy, melatonin, and other behavioral and pharmacological therapies including the melatonin agonist tasimelteon. Management strategies towards each major human circadian sleep-wake rhythm disorder, as outlined in the current International Classification of Sleep Disorders - Third Edition, including jet lag and shift work disorders, delayed and advanced sleep-wake phase rhythm disorders, non-24-h sleep-wake rhythm disorder, and irregular sleep-wake rhythm disorder are summarized. Last, an overview of chronotherapies and the circadian dysregulation of neurodegenerative diseases is reviewed.

Chronotherapeutics: Recognizing the Importance of Timing Factors in the Treatment of Disease and Sleep Disorders

This review describes the characteristics of a number of pathologies, which are considered from the point of view of chronobiology, that is, the way in which biological processes are expressed throughout the 24-hour day. This perspective is a relatively new way of thinking about disease and additionally about how to treat diseases. It has called attention to the importance of not only the quantity of a drug that is administered but also when it is administered. In addition, the review presents an overview of the emerging clinical strategies known as chronotherapeutics, that is, the effects of the daily scheduling of drug administration and the consequences of the activity and efficacy of therapies that are applied in this manner. This article also reviews innovative ways in which physicians are applying time-specified drug treatment (chronopharmacology) for sleep disorders. Here, we present a systematic description of chronopharmacology as well as definitions of key terms that, we believe, will be helpful for newcomers to the field. It is hoped that greater awareness of this new perspective on pharmacology will promote its adoption by researchers and clinicians.

Melatonin for the prevention of postoperative delirium in older adults: a systematic review and meta-analysis

Background

Older surgical patients are at high risk of developing postoperative delirium. Non-pharmacological strategies are recommended for delirium prevention, but no pharmacological agents have compelling evidence to decrease the incidence of delirium. The purpose of this study was to assess whether perioperative melatonin decreases the incidence of delirium in older adults undergoing surgical procedures.

Methods

A systematic search using PubMed/Medline, Embase, PsycINFO, CINAHL, and references of identified articles published in English between January 1990 and October 2017 was performed. Two independent reviewers screened titles and abstracts, and then extracted data following a full-text review of included articles with consensus generation and bias assessment. Studies reporting outcomes for melatonin or ramelteon use to prevent delirium in postoperative hospitalized patients (mean age ≥ 50 years) were eligible for inclusion. Data were pooled using a fixed-effects model to generate a forest plot and obtain a summary odds ratio for the outcome of interest (delirium incidence). Cochran’s Q and I² values were used to investigate heterogeneity.

Results

Of 335 records screened, 6 studies were selected for the qualitative analysis and 6 were included in the meta-analysis (n = 1155). The mean age of patients in included studies ranged from 59 to 84 years. Patients in intervention groups typically received melatonin or ramelteon at daily doses of two to eight milligrams around cardiothoracic, orthopedic, or hepatic surgeries for one to nine days, starting on the evening before or the day of surgery. The incidence of delirium ranged from 0 to 30% in the intervention groups versus 4–33% in the comparator groups, and was significantly reduced in the melatonin group, with a summary effect of the meta-analysis yielding an odds ratio of 0.63 (95% CI 0.46 to 0.87; 0.006; I² = 72.1%). A one study removed analysis reduced overall odds ratio to 0.310 (95% CI 0.19 to 0.50), while reducing heterogeneity (Cochran’s Q = 0.798, I² = 0.000).

Conclusion

Perioperative melatonin reduced the incidence of delirium in older adults in the included studies. While optimal dosing remains an unanswered question, the potential benefit of melatonin and melatonin receptor agonists may make them a reasonable option to use for delirium prevention in older adults undergoing surgical procedures.

Daytime melatonin and light independently affect human alertness and body temperature

Light significantly improves alertness during the night (Cajochen, Sleep Med Rev, 11, 2007 and 453; Ruger et al., AJP Regul Integr Comp Physiol, 290, 2005 and R1413), but results are less conclusive at daytime (Lok et al., J Biol Rhythms, 33, 2018 and 589). Melatonin and core body temperature levels at those times of day may contribute to differences in alerting effects of light. In this experiment, the combined effect of daytime exogenous melatonin administration and light intensity on alertness, body temperature, and skin temperature was studied. The goal was to assess whether (a) alerting effects of light are melatonin dependent, (b) soporific effects of melatonin are mediated via the thermoregulatory system, and (c) light can improve alertness after melatonin-induced sleepiness during daytime. 10 subjects (5 females, 5 males) received melatonin (5 mg) in dim (10 lux) and, on a separate occasion, in bright polychromatic white light (2000 lux). In addition, they received placebo both under dim and bright light conditions. Subjects participated in all four conditions in a balanced order, yielding a balanced within-subject design, lasting from noon to 04:00 pm. Alertness and performance were assessed half hourly, while body temperature and skin temperature were measured continuously. Saliva samples to detect melatonin concentrations were collected half hourly. Melatonin administration increased melatonin concentrations in all subjects. Subjective sleepiness and distal skin temperature increased after melatonin ingestion. Bright light exposure after melatonin administration did not change subjective alertness scores, but body temperature and proximal skin temperature increased, while distal skin temperature decreased. Light exposure did not significantly affect these parameters in the placebo condition. These results indicate that (a) exogenous melatonin administration during daytime increases subjective sleepiness, confirming a role for melatonin in sleepiness regulation, (b) bright light exposure after melatonin ingestion significantly affected thermoregulatory parameters without altering subjective sleepiness, therefore temperature changes seem nonessential for melatonin-induced sleepiness, (c) subjective sleepiness was increased by melatonin ingestion, but bright light administration was not able to improve melatonin-induced sleepiness feelings nor performance. Other (physiological) factors may therefore contribute to differences in alerting effects of light during daytime and nighttime.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Alterations in uteroplacental hemodynamics during melatonin supplementation in sheep and cattle

Compromised placental function can result in fetal growth restriction which is associated with greater risk of neonatal morbidity and mortality. Large increases in transplacental nutrient and waste exchange, which support the exponential increase in fetal growth during the last half of gestation, are dependent primarily on the rapid growth and vascularization of the uteroplacenta. The amplitude of melatonin secretion has been associated with improved oxidative status and altered cardiovascular function in several mammalian species; however, melatonin mediated alterations of uteroplacental capacity in sheep and cattle are lacking. Therefore, our laboratories are examining uteroplacental blood flow and fetal development during maternal melatonin supplementation. Using a mid- to late-gestation ovine model of intrauterine growth restriction, we examined uteroplacental blood flow and fetal growth during supplementation with 5 mg/d of dietary melatonin. Maternal nutrient restriction decreased uterine arterial blood flow, while melatonin supplementation increased umbilical arterial blood flow compared with non-supplemented controls. Although melatonin treatment did not rescue fetal weight in nutrient restricted ewes; we observed disproportionate fetal size and fetal organ development. Elevated fetal concentrations of melatonin may result in altered blood flow distribution during important time points of development. These melatonin specific responses on umbilical arterial hemodynamics and fetal development may be partially mediated through vascular melatonin receptors. Recently, we examined the effects of supplementing Holstein heifers with 20 mg/d of dietary melatonin during the last third of gestation. Uterine arterial blood flow was increased by 25% and total serum antioxidant capacity was increased by 43% in melatonin supplemented heifers vs. non-supplemented controls. In addition, peripheral concentrations of progesterone were decreased in melatonin supplemented heifers vs. non-supplemented controls. Using an in vitro model, melatonin treatment increased the activity of cytochrome P450 2C, a progesterone inactivating enzyme, which was blocked by treatment with the melatonin receptor antagonist, luzindole. Elucidating the consequences of specific hormonal supplements on the continual plasticity of placental function will allow us to determine important endogenous mediators of offspring growth and development.

Critical health psychology in New Zealand: Developments, directions and reflections

We examine how critical health psychology developed in New Zealand, taking an historical perspective to document important influences. We discuss how academic appointments created a confluence of critical researchers at Massey University, how interest in health psychology arose and expanded, how the critical turn eventuated and how connections, both local and international, were important in building and sustaining these developments. We discuss the evolution of teaching a critical health psychology training programme, describe the research agendas and professional activities of academic staff involved and how this sustains the critical agenda. We close with some reflections on progress and attainment.

REVIEW ■ : The Suprachiasmatic Nucleus: A Circadian Oscillator

The suprachiasmatic nucleus (SCN) is considered to be a circadian oscillator that regulates a set of phys iological aspects of behavior, including sleep-wakefulness and hormone release in mammalian species. In this review, we describe recent research that has begun to reveal the functional organization of the SCN. The SCN, which consists of a bilateral pair of tiny nuclei located just above the optic chiasm, contains several kinds of peptidergic neurons, but vasoactive intestinal peptide (VIP), arginine vasopressin (AVP), and somatostatin (SOM) neurons are the main components. VIP neurons and AVP neurons show distinctly different locations in the SCN; the former are found in the ventrolateral portion, whereas the latter are localized in the dorsomedial portion. VIP neurons receive all neuronal inputs from other regions of the CNS, such as those evoked by photic stimulation via the retinal ganglion cells and those relayed by 5HT inner vation from the raphe nuclei. VIP neurons relay their information to other kinds of neurons in the SCN, such as AVP and SOM neurons. VIP neurons, thus, may play a significant role in entrainment of circadian rhythm. VIP, AVP, SOM, and their mRNAs show rhythmic fluctuations that are predicted by this model; VIP and its mRNA show diurnal variation under the influence of photic stimulation, whereas AVP, SOM, and their mRNAs show endogenous rhythms. Immediate early genes (lEGs), such as c-fos mRNA, are also expressed in VIP neurons in the SCN, and IEG expression in the cells appears to be modified by photic stimuli. Together with transplantation studies showing that exogenous SCN tissue tends to restore circadian rhythm in arrhythmic animals, these results are beginning to clarify the function of the SCN in setting, maintaining, and resetting the biological clock. NEUROSCIENTIST 3:215-225, 1997

Melatonin regulates somatotrope and lactotrope function through common and distinct signaling pathways in cultured primary pituitary cells from female primates

Melatonin (MT) is secreted by the pineal gland and exhibits a striking circadian rhythm in its release. Depending on the species studied, some pituitary hormones also display marked circadian/seasonal patterns and rhythms of secretion. However, the precise relationship between MT and pituitary function remains controversial, and studies focusing on the direct role of MT in normal pituitary cells are limited to nonprimate species. Here, adult normal primate (baboons) primary pituitary cell cultures were used to determine the direct impact of MT on the functioning of all pituitary cell types from the pars distalis. MT increased GH and prolactin (PRL) expression/release in a dose- and time-dependent fashion, a response that was blocked by somatostatin. However, MT did not significantly affect ACTH, FSH, LH, or TSH expression/release. MT did not alter GHRH- or ghrelin-induced GH and/or PRL secretions, suggesting that MT may activate similar signaling pathways as ghrelin/GHRH. The effects of MT on GH/PRL release, which are likely mediated through MT1 receptor, involve both common (adenylyl cyclase/protein kinase A/extracellular calcium-channels) and distinct (phospholipase C/intracellular calcium-channels) signaling pathways. Actions of MT on pituitary cells also included regulation of the expression of other key components for the control of somatotrope/lactotrope function (GHRH, ghrelin, and somatostatin receptors). These results show, for the first time in a primate model, that MT directly regulates somatotrope/lactotrope function, thereby lending support to the notion that the actions of MT on these cells might substantially contribute to the define daily patterns of GH and PRL observed in primates and perhaps in humans.

The effectiveness of melatonin for promoting healthy sleep: a rapid evidence assessment of the literature

A systematic review was conducted using Samueli Institute’s Rapid Evidence Assessment of the Literature (REAL^©) process to determine the evidence base for melatonin as an agent to optimize sleep or improve sleep quality, and generalize the results to a military, civilian, or other healthy, active, adult population. Multiple databases were searched yielding 35 randomized controlled trials (RCTs) meeting the review’s inclusion criteria, which were assessed for methodological quality as well as for melatonin effectiveness. The majority of included studies were high quality (83.0%). Overall, according to Grading Recommendations, Assessment Development and Evaluation (GRADE) methodology, weak recommendations were made for preventing phase shifts from jet lag, for improving insomnia in both healthy volunteers and individuals with a history of insomnia, and for initiating sleep and/or improving sleep efficacy. Based on the literature to date, no recommendations for use in shift workers or to improve hormonal phase shift changes in healthy people can be made at this time. Larger and longer-duration RCTs utilizing well characterized products are needed to warrant melatonin recommendations in young, healthy adults.

Pharmacological characterization of a highly selective and potent partial agonist of the MT₂ melatonin receptor

BACKGROUND/AIMS

The MT₂ melatonin receptor is a potential target for treating circadian rhythm sleep disorders. This study aims to characterize the recently identified MT₂ melatonin receptor agonist.

METHODS

The pharmacological properties of the MT₂ melatonin receptor-selective agonist as exemplified by compound 1 [N-(2-[7-benzyl-1,6-dihydro-2H-indeno(5,4-b)furan-8-yl]ethyl)acetamide] were evaluated by use of cell-free binding and cell-based functional assays.

RESULTS

Competition binding assays using 2-[(125)I]iodomelatonin revealed rapid, reversible, and high-affinity binding of compound 1 to human, mouse, and rat MT₂ melatonin receptors. cAMP, ERK1/2, and PathHunter β-arrestin recruitment assays revealed partial agonist activities. However, compound 1 induced a more intense internalization of human MT₂ melatonin receptor than melatonin. Based on studies using structurally related analogs of compound 1, we further demonstrated that the extent of internalization is independent of the intrinsic efficacy of agonists.

CONCLUSION

These findings provide novel insights into the relationship between intrinsic agonist efficacy and agonist-induced internalization and demonstrate that compound 1 could serve as a pharmacological tool for future studies to elucidate the detailed molecular mechanism of MT₂ receptor internalization.

The hormonal Zeitgeber melatonin: role as a circadian modulator in memory processing

The neuroendocrine substance melatonin is a hormone synthesized rhythmically by the pineal gland under the influence of the circadian system and alternating light/dark cycles. Melatonin has been shown to have broad applications, and consequently becoming a molecule of great controversy. Undoubtedly, however, melatonin plays an important role as a time cue for the endogenous circadian system. This review focuses on melatonin as a regulator in the circadian modulation of memory processing. Memory processes (acquisition, consolidation, and retrieval) are modulated by the circadian system. However, the mechanism by which the biological clock is rhythmically influencing cognitive processes remains unknown. We also discuss, how the circadian system by generating cycling melatonin levels can implant information about daytime into memory processing, depicted as day and nighttime differences in acquisition, memory consolidation and/or retrieval.

1,6-Dihydro-2H-indeno[5,4-b]furan derivatives: design, synthesis, and pharmacological characterization of a novel class of highly potent MT₂-selective agonists

A novel series of 1,6-dihydro-2H-indeno[5,4-b]furan derivatives were designed and synthesized as MT(2)-selective ligands. This scaffold was identified as a potent mimic of the 5-methoxy indole core of melatonin, and introduction of a cyclohexylmethyl group at the 7-position of this scaffold afforded an MT(2)-selective ligand 15 (K(i) = 0.012 nM) with high MT(1)/MT(2) selectivity (799). Compound 15 was identified as a potent full agonist for the MT(2) subtype and exhibited reentrainment effects to a new light/dark cycle in ICR mice at 3-30 mg/kg. This result demonstrated the involvement of the MT(2) receptors in chronobiotic activity.

Therapeutics for Circadian Rhythm Sleep Disorders

The sleep-wake cycle is regulated by the interaction of endogenous circadian and homeostatic processes. The circadian system provides timing information for most physiological rhythms, including the sleep and wake cycle. In addition, the central circadian clock located in the suprachiasmatic nucleus of the hypothalamus has been shown to promote alertness during the day. Circadian rhythm sleep disorders arise when there is a misalignment between the timing of the endogenous circadian rhythms and the external environment or when there is dysfunction of the circadian clock or its entrainment pathways. The primary synchronizing agents of the circadian system are light and melatonin. Light is the strongest entraining agent of circadian rhythms and timed exposure to bright light is often used in the treatment of circadian rhythm sleep disorders. In addition, timed administration of melatonin, either alone or in combination with light therapy has been shown to be useful in the treatment of the following circadian rhythm sleep disorders: delayed sleep phase, advanced sleep phase, free-running, irregular sleep wake, jet lag and shift work.

Jet lag, circadian rhythm sleep disturbances, and depression: the role of melatonin and its analogs

Traveling through several time zones results in a constellation of symptoms known as jet lag. These include reduced alertness, daytime fatigue, loss of appetite, reduced cognitive skills, and disruption of the sleep/wake cycle. In susceptible air travel passengers, jet lag may exacerbate affective illness and result in psychiatric morbidity. Dysregulation of circadian rhythms and melatonin secretion represent the common underlying factor in jet lag and other circadian disorders. Recent studies have established the effectiveness of strategically timed administration of melatonin and appropriate timed exposure to environmental schedules including light in counteracting the dysregulation (chronobiologic actions). With the introduction of melatonergic agonists such as ramelteon and tasimelteon, which have both a stronger affinity for MT₁ and MT₂ melatonin receptors and a longer half-life, new therapeutic options now exist for treating the sleep disturbances associated with jet lag. The melatonin analogs are unique inasmuch as they can also enhance daytime alertness. The recently introduced melatonergic antidepressant agomelatine, which has established its supremacy over other antidepressants in having a significant chronobiologic activity, represents a good choice for treating depressive symptoms that are associated with jet lag.

Biphasic flux profiles of melatonin: the Yin-Yang of transdermal permeation enhancement mediated by fatty alcohol enhancers

This study investigates physicochemical processes responsible for the biphasic transdermal flux profiles of melatonin in the presence of saturated fatty alcohols (SFAL) and unsaturated fatty alcohols (USFAL). The first phase melatonin flux (J(1st)) in the presence of USFAL enhancers increased with increase in the number of double bonds and reached a limiting value with two double bonds in the molecule. In case of SFAL enhancers, J(1st) increased with enhancer chain length and log formulation/skin partition coefficients (log Ps), which were calculated using the solubility parameters of various formulation components. But, melatonin flux in the second phase decreased with increase in the enhancer chain length and log P values. On the other hand, the transepidermal water loss (TEWL) from the SFAL treated skin increased drastically in the second phase and correlated with log P value of the enhancer. High TEWL value, indicative of a severely disrupted SC, may help the polar formulation components to accumulate in the SC. As a consequence, the SC polarity could change significantly and reduce the partitioning of lipophilic enhancer and/or melatonin in the second phase. This study demonstrated that an optimal level of barrier disruption enhances the transdermal permeation of drugs, whereas, a drastic barrier disruption impedes transdermal transport.

Ready for takeoff? A critical review of armodafinil and modafinil for the treatment of sleepiness associated with jet lag

Jet lag syndrome (JLS) is a clinical syndrome of disrupted nocturnal sleep and daytime neurocognitive impairment which occurs in the context of rapid transmeridian travel. Many strategies for treatment of JLS exist, and include hypnotics to enhance nocturnal sleep, chronotherapeutic approaches (eg, light therapy, melatonin, or gradual schedule shifting), and alerting agents to counter daytime sleepiness. Safety concerns have prompted renewed interest in managing JLS-associated excessive daytime sleepiness (JLSAEDS). Off-label use of the newer alerting agents modafinil and armodafinil is increasing for this indication, often at the specific request of patients. In order to better evaluate the potential risks and benefits of these medications for the management of JLSAEDS, clinicians must be aware of what is known - and still not known. In this article, the pharmacology and pharmacokinetics of modafinil and armodafinil are reviewed, along with evidence for their efficacy in treating sleepiness associated with narcolepsy, obstructive sleep apnea and shift work sleep disorder. Clinical trial data for use of alerting agents in the management of JLSAEDS are limited to one three-day trial involving armodafinil, dosed in the morning to treat JLSAEDS in the setting of eastbound transmeridian travel. This study showed improvement in objective measures of daytime sleepiness at doses of 50 and 150 mg per day. However, global impression of clinical severity of symptom scores only improved on day 1 for those patients receiving 150 mg, and were otherwise not superior to placebo. Consideration for the use of modafinil or armodafinil for the treatment of sleepiness associated with JLS involves careful integration of patient-reported goals, a review of medical contraindications, and an awareness of rare adverse events. More research is needed in order to identify those who are most likely to benefit from this intervention and better define the risk-benefit ratio for this indication.

The pathophysiology of jet lag

Jet Lag Disorder (JLD) is a recognized circadian rhythm sleep disorder characterized by insomnia or excessive daytime sleepiness (and sometimes general malaise and somatic symptoms) associated with transmeridian jet travel. It is a consequence of circadian misalignment that occurs after crossing time zones too rapidly for the circadian system to keep pace. The thesis of this review is that a rational treatment approach for jet lag can be grounded in an understanding of the biology of the human circadian timekeeping system. An overview of circadian rhythm physiology is presented with special emphasis on the role of light exposure and melatonin secretion in the regulation of circadian timing. Both timed light exposure (or avoidance) and exogenous melatonin administration have been recruited as treatment modalities to accelerate circadian realignment, based on an understanding of their role in circadian physiology. In addition to circadian misalignment, other contributing causes to jet lag are considered including travel-related sleep deprivation and fatigue. Clinical field trials that have tested the application of circadian rhythm based interventions are then reviewed.

Melatonin and its relevance to jet lag

Jet lag is a disorder in which body rhythms are out of phase with the environment because of rapid travel across time zones. Although it often produces minor symptoms it can cause serious problems in those who need to make rapid critical decisions including airline pilots and business travelers. In this article the authors review basic knowledge underlying the body clock, the suprachiasmatic nucleus (SCN) of the hypothalamus, and the manner in which it regulates the sleep/wake cycle. The regulation of melatonin by the SCN is described together with the role of the melatonin receptors which are integral to its function as the major hormonal output of the body clock. Several factors are known that help prevent and treat jet lag, including ensuring adequate sleep, appropriate timing of exposure to bright light and treatment with melatonin. Because travel can cross a variable number of time zones and in two different directions, recommendations for treatment are given that correspond with these different types of travel. In addition to use of bright light and melatonin, other factors including timed exercise, timed and selective diets and social stimuli deserve study as potential treatments. Moreover, new melatonin agonists are currently under investigation for treatment of jet lag.

Efficacy and hypnotic effects of melatonin in shift-work nurses: double-blind, placebo-controlled crossover trial

Background

Night work is associated with disturbed sleep and wakefulness, particularly in relation to the night shift. Circadian rhythm sleep disorders are characterized by complaints of insomnia and excessive daytime sleepiness that are primarily due to alterations in the internal circadian timing system or a misalignment between the timing of sleep and the 24-h social and physical environment.

Methods

We evaluated the effect of oral intake of 5 mg melatonin taken 30 minutes before night time sleep on insomnia parameters as well as subjective sleep onset latency, number of awakenings, and duration of sleep. A double-blind, randomized, placebo-controlled crossover study with periods of 1 night and washouts of 4 days comparing melatonin with placebo tablets was conducted. We tried to improve night-time sleep during recovery from night work. Participants were 86 shift-worker nurses aged 24 to 46 years. Each participant completed a questionnaire immediately after awakening.

Results

Sleep onset latency was significantly reduced while subjects were taking melatonin as compared with both placebo and baseline. There was no evidence that melatonin altered total sleep time (as compared with baseline total sleep time). No adverse effects of melatonin were noted during the treatment period.

Conclusion

Melatonin may be an effective treatment for shift workers with difficulty falling asleep.

Effect of cyclodextrins on the complexation and nasal permeation of melatonin

The inclusion complexation of melatonin (MT) with modified cyclodextrins (CDs) was studied with an objective of improving the solubility and nasal absorption of MT. The formation of inclusion complex of MT with Hydroxypropyl beta CD (HPbeta CD) and randomly methylated beta CD (RMbeta CD) was characterized in solution and solid states by phase solubility and differential scanning calorimetry analyses. The phase solubility data indicate a linear increase in the solubility of MT with CDs demonstrating Higuchi's A(L)-type phase solubility profiles. The effect of CDs on the permeation of MT across EpiAirway(TM)-100 cultures was studied using a modified nonstatic diffusion setup. CDs were employed at different concentrations with 1% w/v micronized MT suspension in hydroxypropyl methyl cellulose (HPMC) vehicle. At low CD concentrations (1% w/v), the permeation of MT from HPMC formulation was significantly increased (125%,p < .001). However, the permeation was significantly reduced when CDs were used at relatively high concentrations (5 to 10% w/v concentration for HPbetaCD and 10% w/v concentration for RMbetaCD,p < .001). All the tissues were viable with good tissue integrity at the end of permeation experiments, as measured by methylthiazoletetrazolium assay and transepithelial electrical resistance measurements. In conclusion, formation of inclusion complex of MT with HPbetaCD and RMbetaCD was demonstrated in solution and solid state. Both HPbetaCD and RM betaCD at 1% w/v concentration were found to improve the nasal permeability of MT from HPMC gel formulations.

Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders. An American Academy of Sleep Medicine review

OBJECTIVE

This the first of two articles reviewing the scientific literature on the evaluation and treatment of circadian rhythm sleep disorders (CRSDs), employing the methodology of evidence-based medicine. In this first part of this paper, the general principles of circadian biology that underlie clinical evaluation and treatment are reviewed. We then report on the accumulated evidence regarding the evaluation and treatment of shift work disorder (SWD) and jet lag disorder (JLD).

METHODS

A set of specific questions relevant to clinical practice were formulated, a systematic literature search was performed, and relevant articles were abstracted and graded.

RESULTS

A substantial body of literature has accumulated that provides a rational basis the evaluation and treatment of SWD and JLD. Physiological assessment has involved determination of circadian phase using core body temperature and the timing of melatonin secretion. Behavioral assessment has involved sleep logs, actigraphy and the Morningness-Eveningness Questionnaire (MEQ). Treatment interventions fall into three broad categories: 1) prescribed sleep scheduling, 2) circadian phase shifting ("resetting the clock"), and 3) symptomatic treatment using hypnotic and stimulant medications.

CONCLUSION

Circadian rhythm science has also pointed the way to rational interventions for the SWD and JLD, and these treatments have been introduced into the practice of sleep medicine with varying degrees of success. More translational research is needed using subjects who meet current diagnostic criteria.

Practice parameters for the clinical evaluation and treatment of circadian rhythm sleep disorders. An American Academy of Sleep Medicine report

The expanding science of circadian rhythm biology and a growing literature in human clinical research on circadian rhythm sleep disorders (CRSDs) prompted the American Academy of Sleep Medicine (AASM) to convene a task force of experts to write a review of this important topic. Due to the extensive nature of the disorders covered, the review was written in two sections. The first review paper, in addition to providing a general introduction to circadian biology, addresses "exogenous" circadian rhythm sleep disorders, including shift work disorder (SWD) and jet lag disorder (JLD). The second review paper addresses the "endogenous" circadian rhythm sleep disorders, including advanced sleep phase disorder (ASPD), delayed sleep phase disorder (DSPD), irregular sleep-wake rhythm (ISWR), and the non-24-hour sleep-wake syndrome (nonentrained type) or free-running disorder (FRD). These practice parameters were developed by the Standards of Practice Committee and reviewed and approved by the Board of Directors of the AASM to present recommendations for the assessment and treatment of CRSDs based on the two accompanying comprehensive reviews. The main diagnostic tools considered include sleep logs, actigraphy, the Morningness-Eveningness Questionnaire (MEQ), circadian phase markers, and polysomnography. Use of a sleep log or diary is indicated in the assessment of patients with a suspected circadian rhythm sleep disorder (Guideline). Actigraphy is indicated to assist in evaluation of patients suspected of circadian rhythm disorders (strength of recommendation varies from "Option" to "Guideline," depending on the suspected CRSD). Polysomnography is not routinely indicated for the diagnosis of CRSDs, but may be indicated to rule out another primary sleep disorder (Standard). There is insufficient evidence to justify the use of MEQ for the routine clinical evaluation of CRSDs (Option). Circadian phase markers are useful to determine circadian phase and confirm the diagnosis of FRD in sighted and unsighted patients but there is insufficient evidence to recommend their routine use in the diagnosis of SWD, JLD, ASPD, DSPD, or ISWR (Option). Additionally, actigraphy is useful as an outcome measure in evaluating the response to treatment for CRSDs (Guideline). A range of therapeutic interventions were considered including planned sleep schedules, timed light exposure, timed melatonin doses, hypnotics, stimulants, and alerting agents. Planned or prescribed sleep schedules are indicated in SWD (Standard) and in JLD, DSPD, ASPD, ISWR (excluding elderly-demented/nursing home residents), and FRD (Option). Specifically dosed and timed light exposure is indicated for each of the circadian disorders with variable success (Option). Timed melatonin administration is indicated for JLD (Standard); SWD, DSPD, and FRD in unsighted persons (Guideline); and for ASPD, FRD in sighted individuals, and for ISWR in children with moderate to severe psychomotor retardation (Option). Hypnotic medications may be indicated to promote or improve daytime sleep among night shift workers (Guideline) and to treat jet lag-induced insomnia (Option). Stimulants may be indicated to improve alertness in JLD and SWD (Option) but may have risks that must be weighed prior to use. Modafinil may be indicated to improve alertness during the night shift for patients with SWD (Guideline).

Jet lag: therapeutic use of melatonin and possible application of melatonin analogs

Each year millions of travelers undertake long distance flights over one or more continents. These multiple time zone flights produce a constellation of symptoms known as jet lag. Familiar to almost every intercontinental traveler is the experience of fatigue upon arrival in a new time zone, but almost as problematic are a number of other jet lag symptoms. These include reduced alertness, nighttime insomnia, loss of appetite, depressed mood, poor psychomotor coordination and reduced cognitive skills, all symptoms which are closely affected by both the length and direction of travel. The most important jet lag symptoms are due to disruptions to the body's sleep/wake cycle. Clinical and pathophysiological studies also indicate that jet lag can exacerbate existing affective disorders. It has been suggested that dysregulation of melatonin secretion and occurrence of circadian rhythm disturbances may be the common links which underlie jet lag and affective disorders. Largely because of its regulatory effects on the circadian system, melatonin has proven to be highly effective for treating the range of symptoms that accompany transmeridian air travel. Additionally, it has been found to be of value in treating mood disorders like seasonal affective disorder. Melatonin acts on MT(1) and MT(2) melatonin receptors located in the hypothalamic suprachiasmatic nuclei, the site of the body's master circadian clock. Melatonin resets disturbed circadian rhythms and promotes sleep in jet lag and other circadian rhythm sleep disorders, including delayed sleep phase syndrome and shift-work disorder. Although post-flight melatonin administration works efficiently in transmeridian flights across less than 7-8 times zones, in the case longer distances, melatonin should be given by 2-3 days in advance to the flight. To deal with the unwanted side effects which usually accompany this pre-departure treatment (acute soporific and sedative effects in times that may not be wanted), the suppression of circadian rhythmicity by covering symmetrically the phase delay and the phase advance portions of the phase response curve for light, together with the administration of melatonin at local bedtime to resynchronize the circadian oscillator, have been proposed. The current view that sleep loss is a major cause of jet lag has focused interest on two recently developed pharmacological agents. Ramelteon and agomelatine are melatonin receptor agonists which, compared to melatonin itself, have a longer half-life and greater affinity for melatonin receptors and consequently are thought to hold promise for treating a variety of circadian disruptions.

The clinical impact of preoperative melatonin on postoperative outcomes in patients undergoing abdominal hysterectomy

BACKGROUND

Melatonin has sedative, analgesic, antiinflammatory, antioxidative, and chronobiotic effects. We determined the impact of oral melatonin premedication on anxiolysis, analgesia, and the potency of the rest/activity circadian rhythm.

METHODS

This randomized, double-blind, placebo-controlled study included 33 patients, ASA physical status I-II, undergoing abdominal hysterectomy. Patients were randomly assigned to receive either oral melatonin 5 mg (n = 17) or placebo (n = 16) the night before and 1 h before surgery. The analysis instruments were the Visual Analog Scale, the State-Trait Anxiety Inventory, and the actigraphy.

RESULTS

The number of patients that needed to be treated to prevent one additional patient reporting high postoperative anxiety and moderate to intense pain in the first 24 postoperative hours was 2.53 (95% CI, 1.41-12.22) and 2.20 (95% CI, 1.26-8.58), respectively. The number-needed-to-treat was 3 (95% CI, 1.35-5.0) to prevent high postoperative anxiety in patients with moderate to intense pain, when compared with 7.5 (95% CI, 1.36-infinity) in the absence of pain or mild pain. Also, the treated patients required less morphine by patient-controlled analgesia, as assessed by repeated measures ANOVA (F[1,31] = 6.05, P = 0.02). The rest/activity cycle, assessed by actigraphy, showed that the rhythmicity percentual of 24 h was higher in the intervention group in the first week after discharge ([21.16 +/- 8.90] versus placebo [14.00 +/- 7.10]; [t = -2.41, P = 0.02]).

CONCLUSIONS

This finding suggested that preoperative melatonin produced clinically relevant anxiolytic and analgesic effects, especially in the first 24 postoperative hours. Also, it improved the recovery of the potency of the rest/activity circadian rhythm.

Influence of dietary melatonin on photoreceptor survival in the rat retina: an ocular toxicity study

Previous studies have shown that melatonin treatment increases the susceptibility of retinal photoreceptors to light-induced cell death. The purpose of this study was to evaluate under various conditions the potential toxicity of dietary melatonin on retinal photoreceptors. Male and female Fischer 344 (non-pigmented) and Long-Evans (pigmented) rats were treated with daily single doses of melatonin by gavage for a period of 14 days early in the light period or early in the dark period. In another group, rats were treated 3 times per week with melatonin early in the light period, and then exposed to high intensity illumination (1000-1500 lx; HII) for 2h, and then returned to the normal cyclic lighting regime. At the end of the treatment periods, morphometric measurements of outer nuclear layer thickness (ONL; the layer containing the photoreceptor cell nuclei) were made at specific loci throughout the retinas. In male and female non-pigmented Fischer rats, melatonin administration increased the degree of photoreceptor cell death when administered during the nighttime and during the day when followed by exposure to HII. There were some modest effects of melatonin on photoreceptor cell death when administered to Fischer rats during the day or night without exposure to HII. Melatonin treatment caused increases in the degree of photoreceptor cell death when administered in the night to male pigmented Long-Evans rats, but melatonin administration during the day, either with or without exposure to HII, had little if any effect on photoreceptor cell survival. In pigmented female Long-Evans rats, melatonin administration did not appear to have significant effects on photoreceptor cell death in any treatment group. The results of this study confirm and extend previous reports that melatonin increases the susceptibility of photoreceptors to light-induced cell death in non-pigmented rats. It further suggests that during the dark period, melatonin administration alone (i.e., no HII exposure) to pigmented male rats may have a toxic effect on retinal cells. These results suggest that dietary melatonin, in combination with a brief exposure to high intensity illumination, induces cellular disruption in a small number of photoreceptors. Chronic exposure to natural or artificial light and simultaneous intake of melatonin may potentially contribute to a significant loss of photoreceptor cells in the aging retina.

Design, synthesis and melatoninergic activity of new unsubstituted and β,β′-difunctionalised 2,3-dihydro-1H-pyrrolo[3,2,1-ij]quinolin-6-alkanamides

A series of new 2,3-dihydro-1H-pyrrolo[3,2,1-ij]quinolin-6-alkanamides, with and without alkyl and cycloalkyl moieties in the beta-position of the alkanamido side chain, have been prepared and tested for their ability to activate pigment granule aggregation in Xenopus laevis melanophores and bind to the recombinant human MT(1) and MT(2) melatonin receptor subtypes expressed in NIH 3T3 cells. An increase of the spacer's length in the side chain by a methylene unit (from 17d to 21d) leads to a six-fold decrease in antagonistic activity. On the other hand, the introduction of two methyl groups in the beta-position of the side chain of 17a induces agonist potency (compound 24), implying thus that the two beta-methyl groups are not only tolerated by the receptor, but constitute functional probes in its dynamic agonist-antagonist conformational equilibrium. The presence of more bulky beta-substituents, regardless of the size of the R group, compounds 24a,b, seems to lead to antagonism and to a noteworthy MT(2) subtype selectivity. Last, the new N1-C7 annulated derivatives presented herein are substantially more potent than their respective N1-C2 annulated counterparts, previously reported.

Strategies to improve sleep during extended search and rescue operations

OBJECTIVE

This study investigated strategies to improve sleeping conditions during search and rescue operations during disaster response.

METHODS

Forty members of the Montgomery County (Maryland) Urban Search and Rescue Team were surveyed for individual sleep habits and sleeping aids used during extended deployments. Team members were also asked to suggest methods to improve sleep on future deployments.

RESULTS

The average amount of sleep during field operations was 5.4 hours with a range of 4-8 hours. Eight percent surveyed would prefer another schedule besides the 12-hour work day, all of whom proposed three 8-hour shifts. Fifteen percent of participants were interested in a pharmacological sleeping aid. Fifty percent of search and rescue members interviewed would consider using nonpharmacological sleeping aids. Furthermore, 40% of participants stated they had successfully devised self-employed methods of sleep aids for previous deployments, such as ear plugs, massage, mental imagery, personal routines, music and headphones, reading, and blindfolds.

CONCLUSIONS

This study suggests that availability of both pharmacological and nonpharmacological sleeping aids to search and rescue workers via the team cache could impact the quantity of sleep. Further investigation into methods of optimizing sleep during field missions could theoretically show enhanced performance through various aspects of missions including mitigation of errors, improved productivity, and improved overall physiological and emotional well-being of search and rescue personnel.