Melatonin administration: effects on rodent circadian rhythms

Previous research has demonstrated a lack of effect of pinealectomy upon the generation of rodent circadian activity rhythms and only a subtle effect upon their reentrainment after phase-shifts of the light-dark cycle. In contrast, our pharmacological studies on melatonin indicate that the pineal gland may be more important than hitherto believed. The main outcome of a preliminary pilot experiment on the effect of daily injections of melatonin, arginine vasotocin, melanocyte-stimulating hormone and a beta-blocker on rat free-running activity rhythms in constant darkness was that melatonin appeared to have entrainment properties. This was clearly demonstrated in a second experiment although entrainment did not occur until the onset of the activity rhythm coincided with the daily injection. In contrast, when melatonin was administered ad lib, in the drinking water to six rats housed in constant dim light, there was apparently a lengthening of the free-running period. The effects of 17 days of melatonin injections given at four different times of day to different groups of rats on re-entrainment of activity rhythms after a 5 h phase-advance of darkness were assessed. Results were confounded by the response of some control rats. However, after an 8 h advance of darkness and daily injection at the time of day of the previous dark onset, melatonin-injected rats phase-advanced, whereas vehicle-injected and uninjected control rats phase-delayed. Thus melatonin can alter the direction, but not necessarily the rate, of re-entrainment. The relevance of some of these findings with pharmacological doses of melatonin to the function of endogenous melatonin is discussed.

Revisiting reliability of quantified perineal ultrasound: Bland and Altman analysis of a new protocol for the rectangular coordinate method

AIMS

This study tested the reliability of a new protocol for the rectangular coordinate method of quantifying perineal ultrasound.

METHODS

Representative scans of healthy primiparous females were quantified by positioning a pubic bone template, drawn onto an acetate sheet containing x-y axes, over scans, by aligning the x-axis with the pubic bone central axis. Values for x (D(x)) and y (D(y)) located the urethrovesical junction (UVJ) at Rest, and at maximal Valsalva and Kegel. Range of motion (V-K) was calculated. Bland and Altman analysis, correlations, and t-tests determined intra- and inter-rater reliability, and variance due to designation of the pubic bone central axis (template control).

RESULTS

Correlations averaged 0.72, 0.70, and 0.92 for intra-rater, inter-rater, and template control experiments. D(x) Rest, D(x) Kegel, and V-K were reliable in all experiments. First and second measures for inter-rater D(y) Rest and D(y) Kegel, and template control D(y) Valsalva were significantly different. Bland and Altman analysis showed D(y) Rest, D(y) Kegel, and D(x) and D(y) Valsalva for both reliability experiments to have limits of agreement (LOA's) large enough to explain >or=50% of the actual value ranges. Template control LOA's explained <or=30% of the actual value ranges.

CONCLUSIONS

The reliability of this protocol varied according to the conditions analyzed; accurate reliability assessment of all conditions required Bland and Altman analysis; and the designation of the pubic bone central axis remained a source of variance between investigators. Our results suggest Bland and Altman analysis be used with each study that quantifies perineal ultrasound.

Gender differences in the cortical electrophysiological processing of visual emotional stimuli

The processing of visual emotional stimuli has been investigated previously; however, gender differences in the processing of emotional stimuli remain to be clarified. The aim of the current study was to use steady-state probe topography (SSPT) to examine steady-state visually evoked potentials (SSVEPs) during the processing of pleasant and unpleasant images relative to neutral images, and to determine whether this processing differs between males and females. Thirty participants (15 males and 15 females) viewed 75 images low on the arousal dimension (categorised as pleasant, neutral or unpleasant) selected from the International Affective Picture System (IAPS), whilst a 13-Hz sinusoidal white visual flicker was superimposed over the visual field and brain electrical activity was recorded from 64 electrode sites. Results suggest that pleasant and unpleasant images relative to neutral images are associated with reductions in frontal latency and occipital amplitude. In addition, electrophysiological gender differences were observed despite there being no differences found between males and females on subjective mood or behavioural ratings of presented images (valence and arousal dimensions). The main gender difference reported in the current study related to the processing of unpleasant images (relative to neutral images) which is associated with widespread frontal latency reductions (predominantly right sided) in females but not in males. Our results suggest that gender differences do exist in the processing of visual emotional stimuli, and illustrate the importance of taking these differences into account during investigations of emotional processing. Finally, these gender differences may have implications for the pathophysiology of mood disorders such as depression.

The effect of repeated pulses of light at the same time on period responses of the rat circadian pacemaker

A consequence of simple velocity-based models is that, in response to light pulses, the circadian period should adjust inversely to phase. In addition, because of the interaction of circadian period and phase response, earlier circadian period changes should modify later circadian period changes. The literature contains few mentions of response curves of circadian period responses following light pulses. Rats were exposed to four pulses of light (60 minutes, 1000 lux) at the same circadian time, a minimum of 26 days apart; we assessed period responses and possible bias in the period-response curve. Modulation of circadian period following light-induced phase responses was examined by assessing the period of running wheel activity onset. Phase and circadian period were not consistently found to share an inverse relationship. Moreover, biases in initial period tended to be increased by the experimental protocol regardless of circadian time of pulse. Rats with a short initial (high-velocity) period had a lengthened period, while rats with a long initial period (low velocity) tended to have a reduce period. However, rats with a long initial period were phase delay biased, not phase advance biased. These results do not support a simple velocity model of the pacemaker.

Melatonin profiles and sleep characteristics in boys with fragile X syndrome: a preliminary study

Sleep patterns and endogenous melatonin profiles in 13 fragile X boys between the age of 4.7 and 11.0 years were compared to those of 8 age-matched, normal control boys. Parents recorded sleep patterns on a Sleep Diary Chart for 14 consecutive days. Twelve saliva samples were obtained from 8 fragile X participants and all of the controls over 48 hours for the assessment of salivary melatonin profiles. The results showed greater variability in total sleep time and difficulty in sleep maintenance in fragile X boys compared with the control participants. Nocturnal melatonin production, expressed as both peak level and area under the concentration-time curve between 20:00 h and 08:00 h, were found to be significantly larger in fragile X boys than in controls. Additionally, the mean of the minimum daytime melatonin levels recorded was significantly higher for the fragile X group. Elevated levels in some fragile X boys relative to the range seen in controls, occurring either during the day or at night, or in both segments of the secretory profile for some individuals, may be due in part to overactivity of the sympathetic nervous system. Alternative molecular mechanisms leading to changes in melatonin profiles in fragile X are also discussed.

Acute increases in night-time plasma melatonin levels following a period of meditation

To determine whether a period of meditation could influence melatonin levels, two groups of meditators were tested in a repeated measures design for changes in plasma melatonin levels at midnight. Experienced meditators practising either TM-Sidhi or another internationally well known form of yoga showed significantly higher plasma melatonin levels in the period immediately following meditation compared with the same period at the same time on a control night. It is concluded that meditation, at least in the two forms studied here, can affect plasma melatonin levels. It remains to be determined whether this is achieved through decreased hepatic metabolism of the hormone or via a direct effect on pineal physiology. Either way, facilitation of higher physiological melatonin levels at appropriate times of day might be one avenue through which the claimed health promoting effects of meditation occur.

A therapeutic role for melatonin antagonism in experimental models of Parkinson's disease

To determine the effects of endogenous and exogenous melatonin on experimental models of Parkinson's disease (PD), Sprague-Dawley rats were exposed to intracerebroventricular implants of slow release melatonin, pinealectomy (PX), or constant light (LL) and then injected with central 6-hydroxydopamine (6-OHDA) or i.p. 1-methyl-4-phenyl,1-1,2,3,6-tetrahydropyridine (MPTP). The resulting impairment of motor function and related behavioural impairment were exacerbated by melatonin implantation, while PX and exposure to LL significantly reduced the severity of experimental PD. These results are consistent with previous work highlighting the importance of aberrant amine production in neurological disease and demonstrate that treatments that reduce endogenous melatonin bioavailability can ameliorate experimental PD. Furthermore, these findings illustrate that melatonin is not the universal remedy that it is currently claimed to be, and may pose considerable problems in neurological diseases characterised by dopamine degeneration.

The effect of multiple pulses of light on the circadian phase response of the rat

Multiple pulses of light administered to humans have been reported to result in type 0 phase responses. These results suggest the underlying pacemaker to be nonsimple. At present, results with this type of protocol have only been reported for humans. Therefore, multiple pulses of light were administered to rats. Rats were exposed to one, two, three, or four pulses of light for 5 h (1000 lux) at successive 24-h intervals. Results did not suggest a type 0 phase response. Nonetheless, results with a second, third, or fourth light exposure were not fully predictable from a phase response curve derived from a single light pulse.

Changes in human plasma melatonin profiles in response to 50 Hz magnetic field exposure

The effects of power-frequency magnetic fields on nighttime plasma melatonin were studied in a group of 30 adult male human subjects. Exposure consisted of 20 microT (200 mG) at 50 Hz (circularly polarized) at certain times in relation to the predicted time of onset of rise in melatonin concentration for a particular individual (the time of onset was predicted from a previous screening night). Response to this exposure was compared to sham-exposure (in random order). When exposure preceded onset of rise, a significant delay in onset time relative to sham-exposure of approximately half an hour was observed, with indications (marginally significant) of a reduction in maximum melatonin level. Analysis of distribution of time-delays is consistent with two populations: those individuals who respond (around 20%) and those that do not. Magnetic fields generated by square-wave currents produce more marked reductions in the maximum level when compared to sinusoidal waveforms, but there was no significant difference in onset time.

Orphan neurones and amine excess: the functional neuropathology of Parkinsonism and neuropsychiatric disease

The aetiology and treatment of Parkinsonism is currently conceptualised within a dopamine (DA) deficiency-repletion framework. Loss of striatal DA is thought to cause motor impairment of which tremor, bradykinaesia and rigidity are prominent features. Repletion of deficient DA should at least minimise parkinsonian signs and symptoms. In Section 2, based on extensive pre-clinical and clinical findings, the instability of this approach to Parkinsonism is scrutinised as the existing negative findings challenging the DA deficiency hypothesis are reviewed and reinterpreted. In Section 3 it is suggested that Parkinsonism is due to a DA excess far from the striatum in the area of the posterior lateral hypothalamus (PLH) and the substantia nigra (SN). This unique area, around the diencephalon/mesencephalon border (DCMCB), is packed with many ascending and descending fibres which undergo functional transformation during degeneration, collectively labelled 'orphan neurones'. These malformed cells remain functional resulting in pathological release of transmitter and perpetual neurotoxicity. Orphan neurone formation is commonly observed in the PLH of animals and in man exhibiting Parkinsonism. The mechanism by which orphan neurones impair motor function is analogous to that seen in the diseased human heart. From this perspective, to conceptualise orphan neurones at the DCMCB as 'Time bombs in the brain' is neither fanciful nor unrealistic [E.M. Stricker, M.J. Zigmond, Comments on effects of nigro-striatal dopamine lesions, Appetite 5 (1984) 266-267] as the DA excess phenomenon demands a different therapeutic approach for the management of Parkinsonism. In Section 4 the focus is on this novel concept of treatment strategies by concentrating on non-invasive, pharmacological and surgical modification of functional orphan neurones as they affect adjacent systems. The Orphan neurone/DA excess hypothesis permits a more comprehensive and defendable interpretation of the interrelationship between Parkinsonism and schizophrenia and other related disorders.

Antibiotic resistance in Streptomyces lividans: fluorescence assay for streptogramin B lyase

A fluorescence assay for streptogramin B lyase, an enzyme that confers resistance to streptogramin B antibiotics, has been developed. The antibiotic substrates are fluorescent and the linear peptide products formed in the lyase-catalyzed reaction are relatively nonfluorescent. The assay has potential for assessing bacterial resistance to streptogramin B antibiotics and will be utilized to direct the purification of streptogramin B lyase from bacterial extracts.

The application of positron emission tomography to the study of the normal menstrual cycle

Positron emission tomography (PET) was used to investigate regions of the brain that are selectively affected during different phases of the normal menstrual cycle. A total of 10 healthy 18-29 year old female volunteers had PET measurements of brain glucose metabolism between days 5 and 9 of the follicular phase when plasma concentrations of oestradiol and progesterone were relatively low and between days 5 and 8 of the luteal phase when plasma concentrations of oestradiol and progesterone were relatively high. Automated algorithms were used to align the PET images in each individual, transform them into the coordinates of a brain atlas, control for variations in whole brain measurements and compute t-score maps of phase-related differences in regional glucose metabolism. The mid-follicular phase was associated with significantly higher glucose metabolism in thalamic, prefrontal, temporoparietal and inferior temporal regions. The mid-luteal phase was associated with significantly higher glucose metabolism in superior temporal, anterior temporal, occipital, cerebellar, cingulate and anterior insular regions. While this study should be considered to be exploratory, it provides normative data for future studies and illustrates how PET can be used to help characterize relationships between phases of the female life cycle, temporally related disorders and local functions of the living human brain.

Daily restricted feeding effects on the circadian activity rhythms of the stripe-faced dunnart, Sminthopsis macroura

The effect of daily restricted feeding (RF) on the circadian wheel-running activity rhythms of the stripe-faced dunnart (Sminthopsis macroura) was examined. Dunnarts were presented with a 2-h meal in the middle of the light period of a 14:10 light:dark (LD) cycle and during constant dim light (LL). No meal-anticipatory activity (AA) was observed in any of the dunnarts during the experiment. This contrasts with previous work where AA has been reported in dunnarts subjected to RF. In LL, RF acted as a weak zeitgeber for the circadian activity rhythms of the dunnart. Evidence supporting this observation was the fact that 4/8 dunnarts' activity rhythms were entrained by RF, 2 showed relative coordination, and 1 exhibited bouncing phenomenon. In other species of marsupials and in rats, it has been proposed that RF entrains a food-entrainable pacemaker, which, in turn, entrains, via coupling, the suprachiasmatic-based, light-entrainable pacemaker. The findings of the present study differ from those reported previously in that no observable AA was entrained but the light-entrainable pacemaker was entrained by RF. In the dunnart, it remains to be determined whether RF directly entrains the light-entrainable pacemaker or whether RF entrains a food-entrainable pacemaker and in turn, via coupling, the light-entrainable pacemaker.

Inhibition of melatonin secretion onset by low levels of illumination

Melatonin is a hormone released during darkness under the control of the hypothalamic circadian pacemaker. It has been shown that melatonin is suppressed by light as a function of intensity, with low levels of illumination producing small effects and more intense light greater, but not complete inhibition. The studies which lead to these conclusions administered light subsequent to the secretion pattern being well established. Light as low as 250 lux administered during the normal onset of secretion can reduce melatonin to below detectable levels. The onset of melatonin secretion was delayed for at least an hour during 250 lux exposure and did not rise until termination of light exposure (two hours after control melatonin onset) with higher illumination (500, 1000 and 2500 lux). This tentatively indicates that duration of the inhibition is intensity dependent. It is suggested that the experimental paradigm used in the present study may be a more realistic representation of the effect of normal light exposure (both natural and artificial) on the circadian system, and that findings may be pertinent to the aetiology of certain sleep onset insomnias, which would include delayed sleep phase syndrome (DSPS) and adaptation to shift work.

Characterization of 16S rRNA genes from oil field microbial communities indicates the presence of a variety of sulfate-reducing, fermentative, and sulfide-oxidizing bacteria

Oil field bacteria were characterized by cloning and sequencing of PCR-amplified 16S rRNA genes. A variety of gram-negative, sulfate-reducing bacteria was detected (16 members of the family Desulfovibrionaceae and 8 members of the family Desulfobacteriaceae). In contrast, a much more limited number of anaerobic, fermentative, or acetogenic bacteria was found (one Clostridium sp., one Eubacterium sp., and one Synergistes sp.). Potential sulfide oxidizers and/or microaerophiles (Thiomicrospira, Arcobacter, Campylobacter, and Oceanospirillum spp.) were also detected. The first two were prominently amplified from uncultured production water DNA and represented 28 and 47% of all clones, respectively. Growth on media containing sulfide as the electron donor and nitrate as the electron acceptor and designed for the isolation of Thiomicrospira spp. gave only significant enrichment of the Campylobacter sp., which was shown to be present in different western Canadian oil fields. This newly discovered sulfide oxidizer may provide a vital link in the oil field sulfur cycle by reoxidizing sulfide formed by microbial sulfate or sulfur reduction.

Chronobiotics--drugs that shift rhythms

A chronobiotic is defined and levels of action within the mammalian circadian pacemaker system, such as the retina, retinohypothalamic tract, geniculohypothalamic tract, suprachiasmatic nuclei, output and feedback systems are identified. Classes of drug that include the indoleamines, cholinergic agents, peptides, and benzodiazepines, which might act as chronobiotics within these levels, are evaluated. Particular emphasis is placed on the indole, melatonin (MLT). The clinical circumstances for use of chronobiotics in sleep disturbances of the circadian kind, such as jet lag, shift work, delayed sleep-phase syndrome, advanced sleep-phase syndrome, irregular and non-24-hr sleep-wake cycles, are described under reorganized headings of disorders of entrainment, partial entrainment, and desynchronization. Specific attention is given to the blind and the aged. Both human and animal studies suggest that MLT has powerful chronobiotic properties. MLT shows considerable promise as a prophylactic and therapeutic alternative or supplement to the use of natural and artificial bright light for resetting the circadian pacemaker. Throughout this discussion, the hypnotic and hypothermic versus the chronobiotic actions of MLT are raised. Finally, problems in the design of delivery systems for MLT are discussed.

Overnight human plasma melatonin, cortisol, prolactin, TSH, under conditions of normal sleep, sleep deprivation, and sleep recovery

Early investigations of the effect of sleep deprivation on plasma melatonin reported no major changes. Recently, 36 hrs of sleep deprivation was reported to elevate melatonin levels on the post-sleep deprivation night. Given these contradictions melatonin, cortisol, prolactin, and thyroid stimulating hormone before, during, and, after sleep deprivation were examined in nine healthy young males following one night of sleep deprivation. Hormone levels at hourly intervals, for each night, were statistically analyzed by a repeated measures, two-way factorial ANOVA. ANOVA was also performed for measures of area under the curve (AUC). No significant differences were observed for melatonin levels. Cortisol was significantly higher on the sleep deprivation night presumably reflecting the aroused state accompanying being awake; however, there were several time points on the control night when it was elevated also. Prolactin was higher on the post-sleep deprivation and control nights but did not rise on the deprivation night, indicating a useful nonpolysomnographic index for discriminating overnight sleep and awake states. TSH levels showed a similar rise during the control and sleep deprivation nights, but remained flat on the post-sleep deprivation night. It appears that the pineal is insulated against feedback from changes to the level of arousal accompanying sleep and wakefulness. In comparison, cortisol, prolactin, and TSH levels vary with these states and are, therefore, useful indices of arousal and sleep-wake.

Dose dependent effects of S-20098, a melatonin agonist, on direction of re-entrainment of rat circadian activity rhythms

The chronobiotic properties of melatonin are well documented. For example, following an 8-h phase advance of the light-dark cycle daily injections of melatonin administered at the pre-shift dark onset alter the direction of re-entrainment of rat activity rhythms. Using this 8-h phase advance paradigm, the effects of the melatonin agonist S-20098 (1 mg/kg and 3 mg/kg) on the rat circadian system were compared with those of melatonin. S-20098 altered the direction of re-entrainment in the same manner as melatonin. A study using lower doses of S-20098 showed that the effect on direction of re-entrainment was dose-dependent, with 100% of rats responding at a dose of 100 micrograms/kg. S-20098 may, therefore, have therapeutic potential as a chronobiotic in the treatment of circadian disorders in humans.

Seasonality in panic disorder

Following a clinical observation of increased anxiety symptoms and mood changes during winter in panic disorder patients, the Seasonal Pattern Assessment Questionnaire (SPAQ) was completed by 133 patients. Global Seasonality Scores (GSS), and the prevalence of Seasonal Affective Disorder (SAD), were significantly higher than reported in general population studies. Seasonal changes were also found in anxiety and panic attacks. These findings suggest the possibility of a common aetiology for panic disorder and SAD, that seasonality may be a far more general phenomenon in psychopathology, and that light therapy may be a useful treatment for some panic disorder patients.

Sleeping patterns during pregnancy in Japanese women

Although sleep disturbance is commonly reported in pregnancy, there have been few studies on sleep characteristics in pregnancy. In this study, all women attending the antenatal clinic at Sapporo Medical College Hospital for 1 month during autumn and 3 months during winter were surveyed with a questionnaire and sleep log. Of the 192 patients, 169 (88.0%) stated that sleep was altered from their usual experience. A principal components analysis identified three sleep factors from the ten items in the measure of sleep used (Sleep Log). The three factors were: Sleep Duration and Quality, Insomnia and Daytime Alertness. Although no significant differences across trimesters were found on the three sleep factors, Sleep Duration and Quality, and Insomnia were worst during the first trimester. Sleep normalized in the second trimester, but the third trimester was characterized by increased Insomnia and decreased Daytime Alertness. The most frequent reasons cited by women for sleep alterations were urinary frequency, backache or ache in the hips and fetal movement. Contingency X2 analyses were used to investigate a relationship between the frequency of reporting the reasons and the trimester of pregnancy. Significant increases were found in reporting as the reasons for sleep difficulties, fetal movement in the third trimester, and heartburn, nausea and vomiting in the first trimester. The description of sleep patterns during pregnancy has clinical relevance as sleep alterations in pregnancy are common.

Circadian wheel running activity rhythms in two strains of domestic rabbit

Results from experiments on two strains of domestic rabbit show that despite their hopping gait, circadian locomotor rhythms can be successfully measured using running wheels specially designed for large laboratory mammals. Three female rabbits of an English outbred strain were monitored in a 13:11 light:dark (LD) cycle and in constant light (LL), while 12 Dutch-Himalayan rabbits were monitored in a 14:10 LD cycle and constant dark (DD). Much stronger rhythms were observed in the latter strain, which under LD conditions showed individuals with patterns that varied from nocturnal (n = 5), diurnal (n = 4), crepuscular (n = 1), and predominantly arrhythmic (n = 2). In DD, 10 rabbits showed strong free-running rhythms, five with tau (tau) less than 24 h and five longer. The predominantly arrhythmic activity pattern in the remaining two made estimation of tau difficult. Differences in circadian patterns both under LD and DD were unrelated to sex. Results show that locomotor rhythms of the rabbit can be measured using the running wheel, the traditional apparatus of chronobiology. However, the experiments suggest also that the large-bodied breed of rabbits that tend towards obesity, such as the English outbred strain, are relatively inactive and that smaller, more active breeds such as the Dutch-Himalayan may be more suitable for studying circadian rhythmicity if the running wheel is employed.

Microbial degradation of phloroglucinol and other polyphenolic compounds

Biodegradation of phloroglucinol (1,3,5-trihydroxybenzene) and other polyphenolic compounds by microbes may occur by aerobic and anaerobic metabolic pathways. Aerobic microbes may initiate the mineralization of phloroglucinol or other polyphenolics by either a reductive pathway, epoxide formation, or a specific hydroxylating mechanism. Cleavage of the various intermediates of phloroglucinol and polyphenolic degradation may occur by intradiol and extradiol mechanisms. The reductive pathway in contrast to other mechanisms utilized by aerobic microbes, seems both cumbersome and energy wasteful. The degradation of lignin and its associated phenolics follows an enzymatic combustion process which resembles a nonspecific enzyme-catalyzed burning. Anaerobic mineralization of phloroglucinol and its associated polyphenolics by several microbes seems to favour the reductive formation of a dihydrophloroglucinol (1,3-dioxo-5-hydroxycyclohexane), which is cleaved by a specific hydrolase. Mineralization of numerous other polyphenolic compounds by anaerobes seems to utilize phloroglucinol as a central metabolite.

Limited effect of three types of daily stress on rat free-running locomotor rhythms

The effects of three types of stress/arousal on rat free-running circadian locomotor rhythms in constant darkness were investigated over a 93-day treatment period. Rats were subjected to 30-min daily immobilisation stress or 30-min novelty or to brief handling (n = 10/group). Seven of the 30 rats exhibited some changes in circadian parameters. Three rats (two immobilised, one handling) showed entrainment, three rats (one from each group) showed a change in tau, and one rat (novelty) showed a phase advance. Thus, in total, 30% immobilisation, 20% percent novelty, and 20% handled rats showed circadian changes. These group changes paralleled changes in faecal boli and body weight, which were taken as indirect indices of the level of stress. Five of the seven changes took place when the end of the active phase (alpha), i.e., subjective dawn, coincided with the time of treatment and the other two when the onset of sigma, i.e., subjective dusk, coincided. Rat circadian locomotor rhythms appear much less susceptible to stress/arousal than those reported for hamsters.

Melatonin and hormonal changes in disturbed sleep during late pregnancy

Although sleep disturbance is commonly reported in pregnancy, there have been surprisingly few studies on the etiology of this condition. Since most hormones show circadian rhythmicity and maintain specific phase relationships with that of the sleep-wake cycle, it was of interest to establish whether sleep disturbances covaried with endocrine changes. This overnight study of pregnant women compared melatonin, cortisol, and prolactin secretion rhythms in six good sleepers and six poor sleepers. The groups were compared by ratios of the areas under the various hormonal curves. Significant differences in the cortisol/melatonin ratio were found between the poor sleeper group (lower values) and the good sleeper group (higher values). Nonsignificant trends, which might be expected to become significant with larger sample sizes, were found for decreased amplitude in the cortisol rhythm and increased amplitude in the melatonin rhythm in poor sleepers. The decreased amplitude of the cortisol rhythm in poor sleepers appeared to be due to a suppression of the early morning (0500-0800) rise. Prolactin levels were high and showed no rhythmicity in both groups. These differences may reflect changes in the circadian pacemaker system of poor sleepers, with increases in melatonin release being a response to counteract poor sleep.

Successful use of S20098 and melatonin in an animal model of delayed sleep-phase syndrome (DSPS)

In human delayed sleep-phase syndrome (DSPS), sleep onset and wake times occur far later than normal. In the population, DSPS may be an important contributor to complaints of sleep onset insomnia. We previously reported an animal model of DSPS in laboratory rats in which the onset of nocturnal activity is delayed by several hours [negative phase angle difference (PAD)]. The effect of melatonin 1 mg/kg SC and S20098 (Servier) 1 and 3 mg/kg on the negative PAD was investigated over 22 days of injections. In comparison to control injections of dimethylsulfoxide (DMSO), both melatonin and S20098 over approximately 9 days phase advanced the onset of activity toward the onset of darkness. At cessation of injections, activity onset delayed over approximately 11 days back toward, but as a group did not reach the original PAD. This effect of melatonin on the phase angle of entrained rats is consistent with its effects on delayed sleep in humans. It is likely, therefore, that S20098 may be of use to ameliorate DSPS in humans.

Abiotic conversion of dihydrophloroglucinol to resorcinol

Chemical conversion of a dihydrophloroglucinol preparation (a mixture of the tautomers 1,3,5-trihydroxy-1,3-cyclohexadiene, 1,3-dioxo-5-hydroxycyclohexane, and 3,5-dihydroxy-3-cyclohexene-1-one) to resorcinol occurred during a 24-h extraction of an acidic (pH 2.0) aqueous dihydrophloroglucinol preparation into ethyl acetate. This conversion did not occur at neutral pH, nor did phloroglucinol (1,3,5-trihydroxybenzene)-induced or succinate-induced Penicillium simplicissimum enzyme extracts convert the dihydrophloroglucinol preparation to resorcinol at pH values of 5.5–8.0. The chemical structure of the dihydrophloroglucinol preparation was determined by gas chromatography - mass spectrometry, high resolution 13C and 1H nuclear magnetic resonance, Fourier-transformed infrared spectrometry, and ultraviolet spectrophotometry. Resorcinol (1,2-dihydroxybenzene) was detected by gas chromatography - mass spectrometry or thin-layer chromatography and ultraviolet spectrophotometry. A chemical mechanism for the conversion of the dihydrophloroglucinol preparation to resorcinol is proposed.Key words: dihydrophloroglucinol, chemical conversion, resorcinol.

Alterations to plasma melatonin and cortisol after evening alprazolam administration in humans

Six healthy volunteers were given a 2-mg dose of alprazolam at 21:00 h and hourly blood samples were collected until 08:00 h the following morning. A control night of hourly blood sampling was undertaken 7 days before Plasma was analyzed for melatonin, cortisol, and alprazolam concentrations. Melatonin concentrations were significantly suppressed by alprazolam at 23:00, midnight, 01:00, 06:00, and 07:00 h. A trend toward suppression was evident from 02:00 to 05:00 h. Cortisol concentrations were also suppressed by alprazolam at several times throughout the night (01:00-04:00 h). Plasma alprazolam levels showed a peak at 3 h and remained relatively high 19-20 h after the dose. The significance of melatonin suppression by alprazolam is discussed in terms of benzodiazepine binding sites and GABA minergic transmission in the human pineal gland, suprachiasmatic nuclei, and retina. Plasma cortisol suppression has been reported for other benzodiazepine drugs, but conflicting data exist for alprazolam. The present results do not support the proposed inhibitory effect of melatonin on the hypothalamic-pituitary-adrenal (HPA)-axis. It is suggested that there is no simple direct relationship between melatonin and the HPA axis in humans.

Melatonin, cortisol and prolactin response to acute nocturnal light exposure in healthy volunteers

An investigation of the cortisol and prolactin responses accompanying acute melatonin suppression by light (600 lux) in humans is described. Light given from midnight to 0300h suppressed nocturnal plasma melatonin concentrations by 65%. Despite this significant suppression of melatonin, no significant effect on plasma cortisol or prolactin concentrations was observed. These data support recent studies which argue that, if there is a relationship between melatonin, the hypothalamo-pituitary, and the hypothalamo-pituitary-adrenal axis in humans, it is neither direct nor simple.

Restricted feeding entrains circadian wheel-running activity rhythms of the kowari

The effect of daily restricted feeding (RF) on the circadian wheel-running rhythms of the kowari, Dasyuroides byrnei, was examined in two experiments. Kowaris were presented with a preferred food (determined in a pilot study) during a daily 2-h meal in the light period of a 14:10 light-dark (LD) cycle (expts 1 and 2), during constant dark (DD) immediately after termination of the LD cycle (expt 1), and during DD when kowaris were free running (expt 1). Results showed that 1) RF elicited anticipatory activity similar in duration and phasing to that observed in the rat; 2) cycles of meal-associated activity free ran for up to 6 days after the termination of RF; 3) activity persists at a phase near that of the former mealtime during periods of food deprivation; and 4) activity indicative of beating between two pacemakers occurred when feeding was restricted to the L period of LD cycles. Together these observations suggest that the activity rhythms of the kowari may be controlled by separate, but possibly coupled, light-entrainable and food-entrainable pacemakers, as are those of the rat.

Melatonin: a chronobiotic with anti-aging properties?

Recently, it has been reported that melatonin administration extends the lifespan of mice, a finding which supports previous research on the effects of pinealectomy and pineal extract administration. The prolongation of lifespan by melatonin has been interpreted in favour of an upregulation of the immune system as well as due to anti-stress properties of melatonin acting via the brain opioid system. In this paper we offer an alternative explanation of melatonin's anti-aging effect: the circadian pacemaker system has a diminished amplitude with age as indexed by a decrease in circulating melatonin levels. Stability of the circadian system correlates with its amplitude and loss of circadian amplitude produces lability which, in turn, leads to internal temporal disorder. Internal temporal disorder may be a precursor of disease states. Exogenous melatonin increases the amplitude of the circadian pacemaker system by feedback onto that system. The hypothalamic suprachiasmatic nuclei are thought to be the mammalian biological clock in the brain and have high concentrations of melatonin receptors. Therefore, melatonin administration in pharmacological doses may prevent aging symptoms by acting at the level of the circadian pacemaker's amplitude.

A Comparative-Study of Circadian Activity Patterns of 2 New Guinean Dasyurid Marsupials, Phascolosorex-Dorsalis and Antechinus-Habbema

Five aspects of the circadian activity rhythm (wheel running, feeding, drinking, duration of time in, and visits to, the nest box) were studied for 129 days in two species of New Guinean dasyurid marsupials that co-exist in mid-montane semi-mossforest. When housed under controlled laboratory conditions, Phascolosorex dorsalis exhibited a diurnal activity pattern whereas Antechinus habbema was nocturnal. Manipulation of the feeding regimen and reversal of the 12: 12 light-dark cycle demonstrated that the diurnal activity of P. dorsalis was not due to synchronisation to food presentation but reflected the behavioural output from an endogenous circadian pacemaker. P. dorsalis appears to be unique among dasyurids in its diurnality. Results are interpreted in terms of the ecological niche being a division of time as well as space.

A portable light source for bright light treatment

A novel, portable, inexpensive bright light source is described. This unit, which has been demonstrated to exhibit physiological effects similar to those of the more conventional light boxes, offers a less restrictive home treatment for patients with seasonal affective disorder and sleep disorders.

Plasma concentrations of melatonin in panic disorder

Nocturnal plasma melatonin concentrations were measured in seven patients with panic disorder and eight healthy control subjects. The five patients who had never received psychotropic medication had significantly greater melatonin concentrations from 4:00 a.m. to 7:00 a.m. than the control subjects. In addition it is possible that a phase delay occurred in these unmedicated patients. The findings are discussed in terms of previous studies showing increased melatonin in manic patients and the effect of intense stress on melatonin synthesis. The two patients who had been medication free for only 1 week showed a decreased melatonin rhythm, which is consistent with previous findings in medicated patients.

Effect of ovariectomy and estradiol on unity of female rat circadian rhythms

Sixteen rats were ovariectomized and given either a 1-cm implant of crystalline estradiol-17 beta (eight rats) or an empty implant (eight rats). A further six rats were sham ovariectomized and given empty implants, and eight rats were left unoperated. The rats were exposed to 70 days of constant dim light (LL) with a maximum illumination level of 20 lx, and circadian running and drinking rhythms were monitored. In LL, both the running and drinking activity rhythms of the ovariectomized, blank-implanted rats became markedly disrupted, whereas unoperated and sham-operated rats maintained unified rhythms. Estradiol-implanted rats developed fewer rhythm desynchronies, and the majority displayed a single band of free-running activity. Rather than being arrhythmic, the activity of the LL-exposed ovariectomized rats appeared to contain several free-running components. Thus these data are consistent with the concept of a multioscillatory basis to the circadian system and support a role for the ovary and its hormone estradiol in the maintenance of coherence between component oscillators.

Melatonin and circadian control in mammals

Although pinealectomy has little influence on the circadian locomotor rhythms of laboratory rats, administration of the pineal hormone melatonin has profound effects. Evidence for this comes from studies in which pharmacological doses of melatonin are administered under conditions of external desynchronization, internal desynchronization, steady state light-dark conditions, and phase shifts of the zeitgeber. Taken together with recent findings on melatonin receptor concentration in the rat hypothalamus, particularly at the level of the suprachiasmatic nuclei, these results suggest that melatonin is a potent synchronizer of rat circadian rhythms and has a direct action on the circadian pacemaker. It is possible, therefore, that the natural role of endogenous melatonin is to act as an internal zeitgeber for the total circadian structure of mammals at the level of cell, tissue, organ, whole organism and interaction of that organism with environmental photoperiod changes.

Phase-response curve to 1-hour light pulses for the marsupial, Dasyuroides byrnei

Most Australian marsupials are nocturnal and consequently it might be expected that the circadian system of this group may be similar to the circadian system of nocturnal rodents. Ten male kowaris (Dasyuroides byrnei) were allowed to free-run in constant darkness and were subsequently administered 1-hour light pulses (1000 lux) at known circadian times in their cycles at intervals of greater than 2 weeks. Changes in the phase of the kowari's circadian rhythm of wheel-running were measured when their rhythms reached a new steady-state after each light pulse and these data were used to construct a phase-response curve to light for the species. The kowari PRC exhibited essentially the same characteristics as those reported for the nocturnal rodents and the marsupial species Sminthopsis macroura. It appears that the kowari entrains its circadian rhythms to light/dark cycles via the discrete phase shifting mechanism as described in nocturnal rodents.

Treatment of seasonal affective disorder with light: preliminary Australian experience

Six patients with a history of Seasonal Affective Disorder (SAD) were treated with bright artificial light. Patients presented with at least two consecutive years of loss of energy, difficulty in working, loss of interest in activities, difficulty in concentrating, increased somnolence, over-eating (carbohydrate craving) and depressed mood. All received seven consecutive days of full-spectrum bright light with an intensity greater than 2,500 lux at a distance of three feet. Evening exposure for two hours resulted in significant clinical improvement. The main improvements were a return to normal sleeping patterns, a reduction in eating habits, improved energy level, a desire to continue with interests and activities and an improvement in mood. Possible mechanisms for the clinical effects of bright light treatment are discussed.

Food-deprivation-induced phase shifts in Sminthopsis macroura froggatti

Past research has shown that there is a circadian oscillator in laboratory rats that is entrained by restricted feeding schedules. However, in laboratory rats at least, the light-dark (LD) cycle is the dominant zeitgeber in the entrainment of wheel-running activity rhythms. Given that dasyurid marsupials are predominantly carnivorous, the episodic intake of food in the wild and the high nutritive content of that food suggest that food may be an important zeitgeber in these species. Twelve Sminthopsis macroura froggatti were presented with a daily meal at 0900 hr under an LD 12:12 cycle with lights-on at 0600 hr for 37 days. Activity in anticipation of the meal was observed in most animals. Following this, all animals were exposed to periods of 12-18 days ad lib. food interspersed with 3-day periods of deprivation--a technique used previously to demonstrate persistent meal-associated rhythms. The meal-associated activity rhythms previously observed in rats during the 3-day deprivation period were not seen, but the 3-day deprivation period produced large phase-shifts in the activity rhythms of several S.m. froggatti. It is concluded that meal feeding does not dominate the LD cycle in entraining dasyurid marsupials, but that the frequent observation of phase shifts suggests a different and, perhaps, stronger role for food intake in biological rhythmicity than has been observed previously in laboratory rats.

Human melatonin response to light at different times of the night

Normal control subjects were examined on three separate occasions with light of sufficient intensity to suppress nocturnal plasma melatonin concentrations. One hour of light was given at each of the following times: (a) 2100-2200h; (b) midnight to 0100h; (c) 0400-0500h. Melatonin synthesis was just becoming apparent at 2100h. There was significant suppression of melatonin by light when given at midnight-0100h and 0400-0500h, but not when light was given at 2100-2200h. In each case following light, melatonin synthesis was shown to resume, even after light applied in the second half of the dark period (0400-0500h). A second experiment was undertaken to examine a possible "rebound" in melatonin levels following light given at 2100-2200h. Six further control subjects were exposed to light at this time, and plasma melatonin levels were measured until 0400h. No rebound in melatonin concentrations was observed. These results are compared with other studies of melatonin response to evening light exposure.

Human melatonin suppression by light is intensity dependent

Five intensities of artificial light were examined for the effect on nocturnal melatonin concentrations. Maximum suppression of melatonin following 1 hr of light at midnight was 71%, 67%, 44%, 38%, and 16% with intensities of 3,000, 1,000, 500, 350, and 200 lux (lx), respectively. In contrast to some previous reports, light of 1,000 lx intensity was sufficient to suppress melatonin to near daytime levels, and intensities down to 350 lx were shown to significantly suppress nocturnal melatonin levels below prelight values. On the basis of these data, it is suggested that when examining the melatonin sensitivity of patient groups (such as bipolar affective disorders) to artificial light, an appropriate light intensity should be established in each laboratory. Light of less intensity (e.g., 200-350 lx) may be more suitable to dichotomize patient groups from control subjects.

Quantal melatonin suppression by exposure to low intensity light in man

Plasma melatonin concentrations were examined following three relatively low intensities of artificial light. Six normal, healthy control subjects were all exposed to (a) 200 lux, (b) 400 lux and (c) 600 lux for a three hour duration from midnight to 0300 h. Blood was also collected on a control night where light intensity was less than 10 lux throughout. Significant suppression of melatonin was observed following light of 400 lux and 600 lux intensity when compared to the control night (p less than 0.05; Mann-Whitney U-test). 200 lux light did not produce a statistically significant melatonin suppression when compared with control samples. Each light intensity produced its own individual maximal melatonin suppression by one hour of exposure. Increased duration of exposure to the light had no further influence on melatonin plasma concentrations. These data confirm a dose response relationship between light and melatonin suppression, and indicate that there is no reciprocal relationship between the effects of light intensity and the duration of exposure on maximal melatonin suppression in man.

Melatonin administration entrains female rat activity rhythms in constant darkness but not in constant light

In female rats the luteinizing hormone (LH) is timed by the circadian system and is followed by a display of intense, estrogen-induced running behavior. This proestrous running on the night of ovulation can be used as a marker of the estrous cycle. Entrainment of the mammalian circadian system by exogenous melatonin (MT) has been demonstrated only in the activity rhythms of male rats. The present experiments were designed to study the effect of daily MT injections on activity rhythms and proestrous running of female rats in 1) continuous dim white light (LL) and 2) continuous darkness (DD). In LL, MT injections (50 micrograms/kg or 1 mg/kg) had no discernible effect on activity rhythms. In DD, four of the six MT-treated rats (100 micrograms/kg) entrained to the injection, and a fifth animal showed phase advances in its activity rhythm when onset of activity passed through injection time. The sixth animal was not injected with MT at activity onset time. None of the six control animals showed either effect. MT had no effect on the length of the estrous cycle. Thus MT injections can entrain circadian rhythms of activity and proestrous running in female rats in DD but not in LL.

Reentrainment of rat circadian activity rhythms: effects of melatonin

Experiments were conducted to determine whether daily melatonin injections could influence reentrainment of circadian locomotor activity rhythms in male Long-Evans rats after phase shifts of the light dark (LD) cycle. When exposed to a 5-h advance of the LD cycle, six out of 15 rats injected daily with melatonin at the new dark onset reentrained by a phase delay of the activity rhythm. The remaining nine melatonin-injected rats and 14 of the 15 control injected rats phase advanced. Daily melatonin injections administered at the old dark onset did not alter direction of reentraining transients but decreased latency to reach steady-state entrainment. In contrast, the effects of melatonin injections given at the end of both the old and new dark periods are difficult to interpret due to the effects of the injection procedure itself at these times. Following an 8-h advance of the LD cycle, all melatonin-injected rats phase advanced while all vehicle and uninjected control rats phase delayed when injections were given at the old dark onset. As has been found in other research areas, the time of day of melatonin administration appears to be a critical factor in its mode of action. It is yet to be established whether these results from the use of pharmacological doses of melatonin are indicative of endogenous melatonin's involvement in the circadian reentrainment mechanism.

Effects of daily melatonin injections on activity rhythms of rats in constant light

Although from pinealectomy studies the pineal body does not appear to participate in the generation of circadian rhythms of mammals, daily injections of the pineal hormone melatonin entrain free-running locomotor activity rhythms of rats in constant darkness. The aim of the present study was to determine whether rats whose circadian activity and drinking rhythms were disrupted in constant light (LL) could be synchronized by daily melatonin administration. Rats were subjected to a regime of gradually increasing photoperiod until they were maintained in LL. Rats whose rhythms became disrupted or showed intact free-running rhythms were injected daily with either melatonin (1 mg/kg) or vehicle (ethanol-saline) solution. Daily melatonin injections either synchronized or partly synchronized disrupted circadian patterns of activity. In contrast to previous findings from experiments conducted in constant darkness, melatonin did not entrain but only partly synchronized intact free-running rhythms. Results are interpreted in terms of melatonin acting on the coupling or phase relationships between oscillators generating circadian locomotor activity rhythms.

Melatonin rhythm in human plasma and saliva

Human plasma and saliva were collected at frequent intervals throughout the night and after a nocturnal challenge by exposure to 3,000 lx of light for 1 h in the middle of the night. Melatonin, as measured by radioimmunoassay, was found to correlate highly in plasma and saliva, described by a linear regression equation: y = 55x-2.6 (r = 0.90). The nocturnal melatonin rhythm in saliva was parallel to that observed in plasma. A good correlation was also observed between plasma and salivary melatonin on exposure to light. Melatonin in both fluids showed a significant fall during light exposure. Levels returned to normal nocturnal values within 2 h after returning to darkness. These results indicate that salivary melatonin, although lower than plasma melatonin, may be used as an index of pineal gland release of melatonin. It is suggested that saliva may be useful as a non-invasive technique for obtaining data on melatonin profiles, especially in pilot-test and screening situations.