Different Renal Chronotoxicity of Bromobenzene and Its Intermediate Metabolites in Mice.

Bromobenzene (BB) is known to pose a serious threat to human health. We previously demonstrated that BB showed chronotoxicity, that is, daily fluctuations in the severity of hepatotoxicity induced in mice. Although BB showed mild nephrotoxicity, a daily fluctuation was not observed in this toxicity. This might be attributed to the fact that BB-induced chronotoxicity is observed only in the liver and not in the kidneys and that the damage caused by BB is prominent in the liver, masking the daily fluctuation in nephrotoxicity. To confirm these two possibilities, we examined the daily fluctuations in nephrotoxicity due to BB intermediate metabolites that target the kidneys: 3-bromophenol, bromohydroquinone, and 4-bromocatechol. Mice were injected with 3-bromophenol, bromohydroquinone, or 4-bromocatechol intraperitoneally at six different time points in a day (zeitgeber time (ZT): ZT2, ZT6, ZT10, ZT14, ZT18, or ZT22). Mortality was monitored for 7 d post-injection. Mice were more sensitive to the acute toxicity of these metabolites around at ZT14 (dark-phase) exposure than around at ZT2 (light-phase) exposure. Furthermore, mice administered with a non-lethal dose of 4-bromocatechol showed significant increases in the levels of plasma blood urea nitrogen and renal malondialdehyde at ZT14 exposure. Moreover, glutathione peroxidase-4, a ferroptosis indicator, was attenuated at ZT14 exposure. These results indicate the toxicity of BB metabolites was higher during the dark-phase exposure, and demonstrate the reason why the diurnal variation of nephrotoxicity by BB was not observed in our previous report is that renal damage was masked due to severe hepatic damage.

Chronobiotic effect of melatonin in experimental optic neuritis.

Optic neuritis (ON) is an inflammatory condition of the optic nerve, which leads to retinal ganglion cell (RGC) loss. A subset of RGCs expressing the photopigment melanopsin regulates non-image-forming visual system (NIFVS) functions such as pupillary light reflex (PLR) and circadian rhythms. Melatonin is a chronobiotic agent able to regulate the circadian system. We analyzed the effect of ON on the NIFVS, and the effect of melatonin on the NIFVS alterations induced by ON. For this purpose, optic nerves from male Wistar rats received vehicle or bacterial lipopolysaccharide (LPS), and one group of animals received a subcutaneous pellet of melatonin or a sham procedure. The NIFVS was analyzed in terms of: i) blue light-evoked PLR, ii) the communication between the retina and the suprachiasmatic nuclei (by anterograde transport, and ex vivo magnetic resonance images), iii) locomotor activity rhythm, and iv) Brn3a(+) and melanopsin(+) RGC number (by immunohistochemistry). Experimental ON significantly decreased the blue light-evoked PLR, induced a misconnection between the retina and the suprachiasmatic nuclei, decreased Brn3a(+) RGCs, but not melanopsin(+) RGC number. A bilateral injection of LPS significantly increased the light (but not dark) phase locomotor activity, rhythm periodicity, and time of offset activity. Melatonin prevented the decrease in blue light-evoked PLR, and locomotor activity rhythm alterations induced by ON. These results support that ON provoked alterations of the circadian physiology, and that melatonin could restore the circadian system misalignment.

Lipolysis and Fat Oxidation Are Not Altered with Presleep Compared with Daytime Casein Protein Intake in Resistance-Trained Women.

BACKGROUND: To date, no studies have directly compared the differences between presleep and daytime protein (PRO) consumption on localized and systemic fat metabolism in active women. OBJECTIVE: The purpose of this study was to assess the effects of presleep compared with daytime PRO supplementation on subcutaneous abdominal adipose tissue (SCAAT) lipolysis and whole-body substrate utilization in women. METHODS: Thirteen young (mean ± SE age: 22 ± 1 y; BMI: 24.3 ± 0.8 kg/m2), resistance-trained [1 repetition maximum (1RM) squat percentage of body weight: 135% ± 6%; 1RM bench press percentage of body weight: 82% ± 4%] women volunteered. On overnight experimental visits, participants performed full-body resistance exercise (RE; 65% 1RM) and were randomly assigned to consume either daytime PRO (PRO, 30 g casein) 30 min post-RE and presleep (30 min before bed) noncaloric, sensory-matched placebo (PLA, 0 g casein) (PRO-PLA), or the opposite (PLA-PRO), switching the order of the supplements on the following visit. SCAAT lipolysis, resting metabolism (indirect calorimetry), and plasma biomarkers (glucose, insulin, nonesterified fatty acids, glycerol) were measured at baseline, overnight, and the next morning. RESULTS: There were no differences in overnight SCAAT lipolysis between conditions indicated by interstitial glycerol concentrations (PRO-PLA: baseline, 669 ± 137; next morning, 321 ± 77.1; PLA-PRO: baseline, 524 ± 109; next morning, 333 ± 68.0 µM), fat oxidation (PRO-PLA: baseline, 5.70 ± 0.35; next morning, 5.00 ± 0.28; PLA-PRO: baseline, 6.59 ± 0.32; next morning, 5.44 ± 0.27 g/min), or any other measure. CONCLUSIONS: There was no difference between the effects of daytime and presleep PRO supplementation on SCAAT lipolysis or whole-body substrate utilization in resistance-trained women. Presleep PRO is a viable option for increasing PRO consumption in resistance-trained women because it does not blunt overnight lipolysis, and will therefore likely not lead to increases in subcutaneous abdominal fat.This trial was registered at clinicaltrials.gov as NCT03573687.

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 intake and potential chronobiological effects on human health.

Melatonin is an indolamine with a recognized chronobiotic role. In turn, the supplementation of melatonin through capsules has been shown to be efficient in the modulation of inflammatory markers, oxidative stress, as well as in the control of hypertension and metabolic syndrome. However, the science of nutrition is interested in the study of the food sources of this hormone and its possible therapeutic effects. Thus, this review aimed to identify and present scientific papers that quantified melatonin in foods and evaluated its application in intervention studies. In total, 278 studies were found, of which 17 were included in this review. The results show that meats, fish, eggs, cereals, tubers, oilseeds, mushrooms, fruits, vegetables, alcoholic and non-alcoholic beverages and dairy products had some items analyzed for their melatonin concentrations. The concentrations reported presented considerable amplitude among different foods and even within the same species, possibly due to differences in cultivation and different hormonal dosing techniques. Also, different concentrations of melatonin can be presented for the same food when submitted to processes such as cooking, roasting or fermentation. The intervention studies presented positive results regarding the consumption of foods rich in melatonin and clinical-metabolic indicators. However, in order to guide nutritional behavior, it is necessary to consult a composition table that makes melatonin concentrations available and considers the processes involved in the preparation of the food. With this table, it will be possible to analyze the real effect of habitual consumption of melatonin from food on health.

Arterial pH and blood gas values in rats under three types of general anesthesia: a chronobiological study.

The aim of study was to review the status of arterial pH, pO(2) and pCO(2) under general anesthesias in dependence on the light-dark (LD) cycle in spontaneously breathing rats. The experiments were performed using three- to four-month-old pentobarbital(P)-, ketamine/xylazine(K/X)- and zoletil(Z)-anesthetized female Wistar rats after a four-week adaptation to an LD cycle (12 h light:12 h dark). The animals were divided into three experimental groups according to the anesthetic agent used: P (light n=11; dark n=8); K/X (light n=13; dark n=11); and Z (light n=18; dark n=26). pH and blood gases from arterial blood were analyzed. In P anesthesia, LD differences in pH, pO(2), and pCO(2) were eliminated. In K/X anesthesia, parameters showed significant LD differences. In Z anesthesia, LD differences were detected for pH and pO(2) only. Acidosis, hypoxia, and hypercapnia have been reported for all types of anesthesia during the light period. In the dark period, except for P anesthesia, the environment was more stable and values fluctuated within normal ranges. From a chronobiological perspective, P anesthesia was not the most appropriate type of anesthesia in these rat experiments. It eliminated LD differences, and also produced a more acidic environment and more pronounced hypercapnia than K/X and Z anesthesias.

[CHRONOBIOLOGICAL ACTIVITY OF AQUEOUS EXTRACTS OF THE ABOVE-GROUND PART OF AGRIMONIA PILOSA L. IN RATS.]

It is established that lithium is accumulated in the above-ground part of agrimony (Agrimoniapilosa L.), the aqueous extract of which exhibits lithium-specific chronobiological activity in rats. The chronobiological study was carried out during the winter solstice on 40 adult male rats divided into three groups: control (intact animals treated with purified water and the extract purified from lithium) and two test groups. Animals in the test groups were administered the aqueous extract of A. pilosa in the morning (8.00 am) and evening (19.00 pm) in amount corresponding to receiving lithium hydroxybutyrate in a dose of 10 mg/kg (p.o.). From the sixth to seventh day of experiment, without canceling this treatment, pilot testing (open field test, rectal temperature measurement) was started at 9 am and continued every 4 h over a period of 48 hours. The primary chronograms were statistically processing by analysis of variance, spectral analysis, and cosinor analysis. The quantitative determination of lithium in the above-ground part of A. pilosa L., its extract and brain of animals was carried out by flame photometry on a SOLAAR Series S spectrometer (Thermo Scientific Co., United States) equipped with a flaming atomizer operating in increased deuterium background correction emission mode. It was found that aqueous extract of the above-ground part of A. pilosa L. contained up to 8.5 ± 0.4 µg/g lithium; in the extract purified by ion-exchange chromatography, this amount was reduced to 1.4 ± 0.2 pg/g. All control animals exhibited external and internal desynchronism. Under the action of herbal extract, the daily dynamics of behavioral activity and rectal temperature in animals acquired a rhythmic character and became consistent with the external day-night cycle.

Chronobiological hypothalamic-pituitary-thyroid axis status and antidepressant outcome in major depression.

BACKGROUND: We previously demonstrated that the difference between 2300h and 0800h TSH response to protirelin (TRH) tests on the same day (ΔΔTSH test) is an improved measure in detecting hypothalamic-pituitary-thyroid (HPT) axis dysregulation in depression. This chronobiological index (1) is reduced in about three quarters of major depressed inpatients, and (2) is normalized after successful antidepressant treatment. In the present study, we examined whether early changes in HPT axis activity during the first 2 weeks of antidepressant treatment could be associated with subsequent outcome. METHODS: The ΔΔTSH test was performed in 50 drug-free DSM-IV euthyroid major depressed inpatients and 50 hospitalized controls. After 2 weeks of antidepressant treatment the ΔΔTSH test was repeated in all inpatients. Antidepressant response was evaluated after 6 weeks of treatment. RESULTS: At baseline, ΔΔTSH values were significantly lower in patients compared to controls and 38 patients (76%) showed reduced ΔΔTSH values (i.e., <2.5mU/L). After 2 weeks of antidepressant treatment, 20 patients showed ΔΔTSH normalization (among them 18 were subsequent remitters), while 18 patients did not normalize their ΔΔTSH (among them 15 were non-remitters) (p<0.00001). Among the 12 patients who had normal ΔΔTSH values at baseline, 8 out 9 who had still normal values after 2 weeks of treatment were remitters, while the 3 with worsening HPT axis function (i.e., reduced ΔΔTSH value after 2 weeks of treatment) were non-remitters (p<0.02). A logistic regression analysis revealed that ΔΔTSH levels after 2 weeks of treatment could predict the probability of remission (odds ratio [OR]=2.11, 95% confidence interval [CI]=1.31-3.41). CONCLUSIONS: Our results suggest that after 2 weeks of antidepressant treatment: (1) chronobiological restoration of the HPT axis activity precedes clinical remission, and (2) alteration of the HPT axis is associated with treatment resistance.

Chronobiology of ethanol: animal models.

Clinical and epidemiological observations have revealed that alcohol abuse and alcoholism are associated with widespread disruptions in sleep and other circadian biological rhythms. As with other psychiatric disorders, animal models have been very useful in efforts to better understand the cause and effect relationships underlying the largely correlative human data. This review summarizes the experimental findings indicating bidirectional interactions between alcohol (ethanol) consumption and the circadian timing system, emphasizing behavioral studies conducted in the author's laboratory. Together with convergent evidence from multiple laboratories, the work summarized here establishes that ethanol intake (or administration) alters fundamental properties of the underlying circadian pacemaker. In turn, circadian disruption induced by either environmental or genetic manipulations can alter voluntary ethanol intake. These reciprocal interactions may create a vicious cycle that contributes to the downward spiral of alcohol and drug addiction. In the future, such studies may lead to the development of chronobiologically based interventions to prevent relapse and effectively mitigate some of the societal burden associated with such disorders.

Melatonin has differential effects on age-induced stoichiometric changes in daily chronomics of serotonin metabolism in SCN of male Wistar rats.

Suprachiasmatic nucleus (SCN) controls various physiological, endocrine and behavioral functions by regulating conversion of serotonin (5-HT) to melatonin (MEL). Aging leads to alterations in the neural and temporal organization of the SCN leading to circadian dysfunction. Age-induced stoichiometric alterations in daily chronomics of various components of 5-HT metabolism were studied by constructing interactomes between parameters. The levels of tryptophan (TRP), 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT), N-acetylserotonin (NAS), N-acetyl 5-methoxytryptamine (MEL), 5-hydroxyindoleacetic acid (5-HIAA), 5-methoxyindole acetic acid (5-MIAA), 5-hydroxytryptophol (5-HTOH), 5-methoxytryptophol (5-MTOH) and N-acetyltryptamine (NAT) were measured at (Zeitgeber time 0, 6, 12 and 18) in male rat SCN of 3, 12 and 24 months age groups. Age-induced decrease was observed in mean levels of NAS, MEL, 5-HIAA, 5-MIAA, 5-MTOH, and NAT and increase was observed in TRP, 5-HTP, 5-HT and 5-HTOH in rat SCN. Daily pulses decreased with aging significantly for TRP, 5-HT, NAS, MEL, 5-HIAA, 5-MIAA and NAT. We report here, the age-induced change in interactions between various 5-HT metabolism components by middle age (12 m) changing further by 24 m. The daily rhythms persisted with aging for NAS, MEL and 5-HTOH. Though, rhythms were abolished for TRP, 5-HTP, 5-HIAA, 5-MIAA, 5-MTOH and NAT differentially at 12 and 24 m. The MEL administration showed restoration in 5-HT ratio with 5-HTP, MEL and 5-HTOH in 24 m and NAS and 5-HIAA in 12 m SCN. Thus, MEL administration effects alterations of age-induced stoichiometry in levels and chronomics of serotonin metabolic network interactomes.

Disrupted chronobiology of sleep and cytoprotection in obesity: possible therapeutic value of melatonin.

From a physiological perspective the sleep-wake cycle can be envisioned as a sequence of three physiological states (wakefulness, non-rapid eye movement, NREM, sleep and REM sleep) which are defined by a particular neuroendocrine-immune profile regulating the metabolic balance, body weight and inflammatory responses. Sleep deprivation and circadian disruption in contemporary "24/7 Society" lead to the predominance of pro-orexic and proinflammatory mechanisms that contribute to a pandemic metabolic syndrome (MS) including obesity, diabetes and atherosclerotic disease. Thus, a successful management of MS may require a drug that besides antagonizing the trigger factors of MS could also correct a disturbed sleep-wake rhythm. This review deals with the analysis of the therapeutic validity of melatonin in MS. Melatonin is an effective chronobiotic agent changing the phase and amplitude of the sleep/wake rhythm and having cytoprotective and immunomodulatory properties useful to prevent a number of MS sequels. Several studies support that melatonin can prevent hyperadiposity in animal models of obesity. Melatonin at a low dose (2-5 mg/day) has been used for improving sleep in patients with insomnia and circadian rhythm sleep disorders. More recently, attention has been focused on the development of potent melatonin analogs with prolonged effects (ramelteon, agomelatine, tasimelteon, TK 301). In clinical trials these analogs were employed in doses considerably higher than those usually employed for melatonin. In view that the relative potencies of the analogs are higher than that of the natural compound, clinical trials employing melatonin doses in the range of 50-100 mg/day are needed to assess its therapeutic value in MS.

[Neurophysiological, neurochemical, autonomous and chronobiological basics of sleep medicine].

The review discusses various mechanisms of the rapidly growing problem of Sleep Medicine. The "Sleep-wakefulness" cycle is a continuum of different functional states and the diseases that these states might prompt to manifest themselves in various ways. In these cases, we must say that change produces the conditions of disease manifestation rather than the disease itself. The paper describes the dynamics of the autonomous parameters during sleep, emphasizes the role and importance of chronobiological aspects of the "sleep-wakefulness" cycle. The holographic principle of the operation I sleep cycle is described which persists even in the cerebral stroke. From the standpoint of neurochemistry, modern hypnotics and drugs of the nearest future can be divided into 2 groups: proS (pro sleep)--for sleeping, and antiW (anti-wakefulness)--vs. wakefulness.

Pitfalls in chronobiology: a suggested analysis using intrathecal bupivacaine analgesia as an example.

BACKGROUND: The duration of analgesia from epidural administration of local anesthetics to parturients has been shown to follow a rhythmic pattern according to the time of drug administration. We studied whether there was a similar pattern after intrathecal administration of bupivacaine in parturients. In the course of the analysis, we came to believe that some data points coincident with provider shift changes were influenced by nonbiological, health care system factors, thus incorrectly suggesting a periodic signal in duration of labor analgesia. We developed graphical and analytical tools to help assess the influence of individual points on the chronobiological analysis. METHODS: Women with singleton term pregnancies in vertex presentation, cervical dilation 3 to 5 cm, pain score >50 mm (of 100 mm), and requesting labor analgesia were enrolled in this study. Patients received 2.5 mg of intrathecal bupivacaine in 2 mL using a combined spinal-epidural technique. Analgesia duration was the time from intrathecal injection until the first request for additional analgesia. The duration of analgesia was analyzed by visual inspection of the data, application of smoothing functions (Supersmoother; LOWESS and LOESS [locally weighted scatterplot smoothing functions]), analysis of variance, Cosinor (Chronos-Fit), Excel, and NONMEM (nonlinear mixed effect modeling). Confidence intervals (CIs) were determined by bootstrap analysis (1000 replications with replacement) using PLT Tools. RESULTS: Eighty-two women were included in the study. Examination of the raw data using 3 smoothing functions revealed a bimodal pattern, with a peak at approximately 0630 and a subsequent peak in the afternoon or evening, depending on the smoother. Analysis of variance did not identify any statistically significant difference between the duration of analgesia when intrathecal injection was given from midnight to 0600 compared with the duration of analgesia after intrathecal injection at other times. Chronos-Fit, Excel, and NONMEM produced identical results, with a mean duration of analgesia of 38.4 minutes (95% CI: 35.4-41.6 minutes), an 8-hour periodic waveform with an amplitude of 5.8 minutes (95% CI: 2.1-10.7 minutes), and a phase offset of 6.5 hours (95% CI: 5.4-8.0 hours) relative to midnight. The 8-hour periodic model did not reach statistical significance in 40% of bootstrap analyses, implying that statistical significance of the 8-hour periodic model was dependent on a subset of the data. Two data points before the change of shift at 0700 contributed most strongly to the statistical significance of the periodic waveform. Without these data points, there was no evidence of an 8-hour periodic waveform for intrathecal bupivacaine analgesia. CONCLUSION: Chronobiology includes the influence of external daily rhythms in the environment (e.g., nursing shifts) as well as human biological rhythms. We were able to distinguish the influence of an external rhythm by combining several novel analyses: (1) graphical presentation superimposing the raw data, external rhythms (e.g., nursing and anesthesia provider shifts), and smoothing functions; (2) graphical display of the contribution of each data point to the statistical significance; and (3) bootstrap analysis to identify whether the statistical significance was highly dependent on a data subset. These approaches suggested that 2 data points were likely artifacts of the change in nursing and anesthesia shifts. When these points were removed, there was no suggestion of biological rhythm in the duration of intrathecal bupivacaine analgesia.

The influence of time of day of administration on duration of opioid labor analgesia.

BACKGROUND: Medications administered into the epidural or intrathecal space for labor analgesia may demonstrate variable effects dependent on time of day, and this may affect clinical research trials investigating the pharmacology of specific drugs. In this retrospective study, we evaluated the effect of time of day of administration of intrathecal fentanyl and systemic hydromorphone labor analgesia from data collected as part of a randomized clinical trial examining the influence of analgesia method on labor outcome. METHODS: Six hundred ninety-two healthy parturients were randomized early in labor to receive combined spinal-epidural (intrathecal fentanyl 25 µg followed by a lidocaine and epinephrine containing epidural test dose) versus systemic (hydromorphone 1 mg IV and 1 mg IM) labor analgesia at first analgesia request. No further analgesics were administered until the patient requested additional analgesia (second analgesia request). Subjects were assigned to the daytime group (DAY) if initial analgesia (neuraxial or systemic) was administered between the hours of 07:01 and 23:00 and to the nighttime group (NIGHT) if it was administered between 23:01 and 07:00. Within each mode of analgesia study arm (neuraxial or systemic), the DAY and NIGHT groups were compared. The primary outcome variable was analgesia duration, defined as the time interval from administration of labor analgesia until the second analgesia request. Cervical dilation at first and second analgesia requests, pain score at first analgesia request, and average amount of pain between analgesia administration and second analgesia request were also compared between DAY and NIGHT groups. Rhythm analyses for duration of analgesia, cervical dilation, and pain scores were performed. RESULTS: There was no difference in the median duration of either neuraxial or systemic analgesia in DAY versus NIGHT subjects, and no harmonic variation was observed for analgesia duration. Rhythm analysis demonstrated a 24-h harmonic cycle for cervical dilation at first analgesia request with maximum values occurring near 17:00 and minimum values near 05:00, but the amplitude of the difference was very small. Rhythm analysis demonstrated a 24-h harmonic cycle with maximum values occurring near 22:00 and minimum values near 10:00 for the average amount of pain between analgesia administration and second analgesia request in neuraxial group patients, but amplitude was small. CONCLUSIONS: Time of day of administration did not seem to influence combined spinal-epidural or systemic labor analgesia duration under these study conditions.

Chronobiological characteristics of painful diabetic neuropathy and postherpetic neuralgia: diurnal pain variation and effects of analgesic therapy.

Clinical impressions suggest that neuropathic pain is often worse at night and significantly impairs sleep. However, the temporal pattern of neuropathic pain during waking hours has not been clearly characterized. Using clinical trial data, we have evaluated the diurnal variation of pain intensity before and during analgesic treatment in patients with diabetic neuropathy (DN) and postherpetic neuralgia (PHN). Pain intensity (0-10) measures throughout the day from a placebo-controlled trial of around-the-clock administration of gabapentin, morphine and a gabapentin-morphine combination in neuropathic pain patients were examined. Baseline data in untreated patients revealed no effect of day of week but a significant effect of time of day in both DN (P < 0.001) and PHN (P < 0.001) such that pain intensity progressively increases throughout the day. This temporal pattern is essentially preserved during treatment with gabapentin, morphine and their combination. Neuropathic pain intensity progressively increases throughout the day and this temporal profile appears to be unaffected by treatment with gabapentin and/or morphine. Advancing our understanding of the chronobiology of neuropathic pain may shed new light on various neurohormonal and neurophysiologic influences and lead to the identification of novel therapeutic targets. Furthermore, recognizing diurnal pain patterns may guide treatment strategies such as the targeted timing of analgesic therapies.

Interaction between ethanol and diazepam in mice: chronobiological aspects.

The mechanism of action of benzodiazepines and ethanol demonstrates that these agents can synergistically affect the central nervous system (CNS). The effects of both ethanol and diazepam are likely to depend on the time of the day when they were administered. Diazepam influence on ethanol-induced sleeping and hypothermic activity in mice as well as the influence of combined administration of these agents on spontaneous locomotor activity and coordination in mice (rota-rod) were investigated. Experiments were carried out in the light phase (10:00-12:00 h) and the dark phase (22:00-24:00 h). It was shown that ethanol-induced sleeping time was longer in the dark phase than the light phase, and that ethanol increased spontaneous locomotor activity both in the light and the dark. Ethanol-induced hypothermia was lower in the dark than in the light. Diazepam decreased locomotor activity more strongly in the dark phase than by day. It impaired the hypothermic action of ethanol in the light phase, but did not have such an effect in the dark phase. Diazepam prolonged ethanol-induced sleep in the light phase, enhanced its action on locomotor coordination and decreased the stimulating effect of ethanol on spontaneous locomotor activity in mice. The chronobiological effect of the interaction between diazepam and ethanol seems to be of practical importance (sleep and motor coordination).

Melatonin as a chronobiotic.

Melatonin, hormone of the pineal gland, is concerned with biological timing. It is secreted at night in all species and in ourselves is thereby associated with sleep, lowered core body temperature, and other night time events. The period of melatonin secretion has been described as 'biological night'. Its main function in mammals is to 'transduce' information about the length of the night, for the organisation of daylength dependent changes, such as reproductive competence. Exogenous melatonin has acute sleepiness-inducing and temperature-lowering effects during 'biological daytime', and when suitably timed (it is most effective around dusk and dawn) it will shift the phase of the human circadian clock (sleep, endogenous melatonin, core body temperature, cortisol) to earlier (advance phase shift) or later (delay phase shift) times. The shifts induced are sufficient to synchronise to 24 h most blind subjects suffering from non-24 h sleep-wake disorder, with consequent benefits for sleep. Successful use of melatonin's chronobiotic properties has been reported in other sleep disorders associated with abnormal timing of the circadian system: jetlag, shiftwork, delayed sleep phase syndrome, some sleep problems of the elderly. No long-term safety data exist, and the optimum dose and formulation for any application remains to be clarified.

Chronobiotic protocol and circadian sleep propensity index: new tools for clinical routine and research on melatonin and sleep.

Twenty years ago, chronobiology was a major topic in medical research, especially in psychiatry. Over time, however, clinicians lost interest in the subject because studies had failed to lead to any practical benefits for patient diagnosis or therapy. Today, the field of chronobiology appears to be on the verge of a renaissance. Over the past decade, our understanding of the basic mechanisms of the circadian timing system (CTS) has increased so rapidly that experts in the field sometimes speak of a "clockwork explosion." It has become apparent that, in order to treat circadian rhythm disturbances, new diagnostic tools are needed so that researchers and physicians can make reliable measurements of CTS functionality (e.g., phase position and circadian rhythm amplitude). Although clinicians do have a phase marker for the CTS at their disposal, there are still no reliable markers for CTS output strength as measured by rhythm amplitude. The amplitude is considered to be the most important factor in CTS output because it determines the degree of temporal organization in human and animal physiology. In this paper, we would like to suggest that circadian sleep propensity (CSP) - the endogenously generated 24-hour variation in the drive to wakefulness and sleep - is the product of all circadian rhythms, serving the human brain at night by assisting it in the production of good-quality sleep. If this is indeed the case, developing a CSP index (CSPI) for use in routine polysomnography would be of great value. In addition, we will review current data on melatonin and its relationship to sleep, basing our analysis on the assumption that melatonin is a circadian hormone and a drug with highly time-dependent effects. Because of this special mode of action, future melatonin studies should employ a special chronobiotic protocol that precludes the use of crossover designs and requires outcome measures different from those used in studies on classical hypnotics.