Misaligned Feeding May Aggravate Pain by Disruption of Sleep-Awake Rhythm.

BACKGROUND: Increasing evidence suggests that patients with eating disorders are more likely to develop chronic pain. A misaligned diet has been reported to disrupt the sleep-awake rhythms. Combined with our previous investigation on circadian pain, we aimed to investigate the role of misaligned diet in the pain sensitivity and the underlying mechanisms. METHODS: Two-month-old C57BL/6J male mice were administered chronic constriction injury (CCI) surgery to establish neuropathic pain models. CCI mice were randomized to scheduled food access throughout the whole day (CCI-free), during the daytime (CCI-misaligned), and at night (CCI-aligned), respectively. The paw withdrawal mechanical threshold, indicating pain behavior, was measured by Von Frey. The gross motor activity pattern indicating the sleep-awake rhythm was monitored by Mini-Mitter. Melatonin (Mel) was administered to ameliorate the sleep-awake rhythm (CCI-free + Mel and CCI-misaligned + Mel). The expressions of circadian pain-related proteins were detected by quantitative polymerase chain reaction and western blot. The primary outcome is the pain threshold and the secondary outcome is the sleep-awake rhythm. RESULTS: Misaligned diet during the peri-CCI surgery period significantly decreased the paw withdrawal mechanical threshold compared with the CCI-free mice (day 14: 0.40 ± 0.09 vs 0.64 ± 0.15; P = .03;) and altered the sleep-awake rhythm. Mel pretreatment alleviated the increased pain (day 14, CCI-misaligned + Mel versus CCI-misaligned: day 14: 0.60 ± 0.13 vs 0.35 ± 0.12; P = .022) and the disrupted sleep-awake rhythm caused by misaligned feeding. The mRNA levels of N-methyl-D-aspartate receptor subtype 2B (NR2B), Ca/calmodulin-dependent protein kinase II (CaMKII), and cyclic adenosine monophosphate-response element binding protein (CREB) in the spinal dorsal horn increased in CCI-misaligned mice compared with the CCI-free mice. The phosphor-NR2B, phosphor-CaMKII, and phosphor-CREB also increased in CCI-misaligned mice compared with the CCI-free mice. However, the expressions of NR2B, CaMKII, and CREB were decreased in CCI-misaligned + Mel mice compared to CCI-misaligned mice at both transcriptional and translational levels. CONCLUSIONS: Misaligned diet might aggravate pain sensitivity through the disruption of the sleep-awake cycle, which could be recovered by Mel. NR2B-CaMKII-CREB may participate in the disruption of sleep-awake rhythm-mediated pain aggravation.

Disharmony between wake- and respiration-promoting activities: effects of modafinil on ventilatory control in rodents.

BACKGROUND: Modafinil is a wake-promoting drug and has been widely used for daytime sleepiness in patients with narcolepsy and other sleep disorders. A recent case series reported that daily oral modafinil alleviated hypercapnic respiratory failure in patients with COPD. However, the precise action of modafinil on respiration such as hypercapnic and/or hypoxic ventilatory responses remains unclear. The aim of this study is to clarify the effect of modafinil on the ventilatory control. METHODS: We investigated the hypothesis that modafinil enhances resting ventilation as well as the stimulatory ventilatory responses to hypercapnia and hypoxia. We addressed the issue by examining minute ventilation, respiratory rate and volume components using plethysmography, combined with a concurrent EEG monitoring of the level of wakefulness before and after administration of modafinil in two doses of 100 mg/kg and 200 mg/kg in unanesthetized mice. In addition, we monitored the effect of the lower dose of modafinil on mice locomotor activity in a freely moving condition by video-recording. RESULTS: Wakefulness, locomotor activity and variability of the breathing pattern in tidal volume were promoted by both doses of modafinil. Neither dose of modafinil increased the absolute values of resting ventilation or promoted the ventilatory responses to hypercapnia and hypoxia. Rather, higher dose of modafinil slightly suppressed respiratory rate in room air condition. CONCLUSIONS: Modafinil is conducive to the state of wakefulness but does not augment resting ventilation or the hyperventilatory responses to chemical stimuli in unanesthetized rodents.

General anesthesia alters time perception by phase shifting the circadian clock.

Following general anesthesia, people are often confused about the time of day and experience sleep disruption and fatigue. It has been hypothesized that these symptoms may be caused by general anesthesia affecting the circadian clock. The circadian clock is fundamental to our well-being because it regulates almost all aspects of our daily biochemistry, physiology, and behavior. Here, we investigated the effects of the most common general anesthetic, isoflurane, on time perception and the circadian clock using the honeybee (Apis mellifera) as a model. A 6-h daytime anesthetic systematically altered the time-compensated sun compass orientation of the bees, with a mean anticlockwise shift in vanishing bearing of 87° in the Southern Hemisphere and a clockwise shift in flight direction of 58° in the Northern Hemisphere. Using the same 6-h anesthetic treatment, time-trained bees showed a delay in the start of foraging of 3.3 h, and whole-hive locomotor-activity rhythms were delayed by an average of 4.3 h. We show that these effects are all attributable to a phase delay in the core molecular clockwork. mRNA oscillations of the central clock genes cryptochrome-m and period were delayed by 4.9 and 4.3 h, respectively. However, this effect is dependent on the time of day of administration, as is common for clock effects, and nighttime anesthesia did not shift the clock. Taken together, our results suggest that general anesthesia during the day causes a persistent and marked shift of the clock effectively inducing "jet lag" and causing impaired time perception. Managing this effect in humans is likely to help expedite postoperative recovery.

Notch-inducible hyperphosphorylated CREB and its ultradian oscillation in long-term memory formation.

Notch is a cell surface receptor that is known to regulate developmental processes by establishing physical contact between neighboring cells. Many recent studies show that it also plays an important role in the formation of long-term memory (LTM) in adults, implying that memory formation requires regulation at the level of cell-cell contacts among brain cells. Neither the target of Notch activity in LTM formation nor the underlying mechanism of regulation is known. We report here results of our studies in adult Drosophila melanogaster showing that Notch regulates dCrebB-17A, the CREB protein. CREB is a transcriptional factor that is pivotal for intrinsic and synaptic plasticity involved in LTM formation. Notch in conjunction with PKC activity upregulates the level of a hyperphosphorylated form of CREB (hyper-PO4 CREB) and triggers its ultradian oscillation, both of which are linked to LTM formation. One of the sites that is phosphorylated in hyper-PO4 CREB is serine 231, which is the functional equivalent of mammalian CREB serine 133, the phosphorylation of which is an important regulator of CREB functions. Our data suggest the model that Notch and PKC activities generate a cyclical accumulation of cytoplasmic hyper-PO4 CREB that is a precursor for generating the nuclear CREB isoforms. Cyclical accumulation of CREB might be important for repetitive aspects of LTM formation, such as memory consolidation. Because Notch, PKC, and CREB have been implicated in many neurodegenerative diseases (e.g., Alzheimer's disease), our data might also shed some light on memory loss and dementia.

The mammalian circadian clock in the suprachiasmatic nucleus exhibits rapid tolerance to ethanol in vivo and in vitro.

BACKGROUND: Ethanol (EtOH) triggers cellular adaptations that induce tolerance in many brain areas, including the suprachiasmatic nucleus (SCN), the site of the master circadian clock. EtOH inhibits light-induced phase shifts in the SCN in vivo and glutamate-induced phase shifts in vitro. The in vitro phase shifts develop acute tolerance to EtOH, occurring within minutes of initial exposure, while the in vivo phase shifts exhibit no evidence of chronic tolerance. An intermediate form, rapid tolerance, is not well studied but may predict subsequent chronic tolerance. Here, we investigated rapid tolerance in the SCN clock. METHODS: Adult C57BL/6 mice were provided 15% EtOH or water for one 12-hour lights-off period. For in vitro experiments, SCN-containing brain slices were prepared in the morning and treated for 10 minutes with glutamate +/- EtOH the following night. Single-cell neuronal firing rates were recorded extracellularly during the subsequent day to determine SCN clock phase. For in vivo experiments, mice receiving EtOH 24 hours previously were exposed to a 30-minute light pulse immediately preceded by intraperitoneal saline or 2 g/kg EtOH injection. Mice were then placed in constant darkness and their phase-shifting responses measured. RESULTS: In vitro, the SCN clock from EtOH-exposed mice exhibited rapid tolerance, with a 10-fold increase in EtOH needed to inhibit glutamate-induced phase shifts. Co-application of brain-derived neurotrophic factor prevented EtOH inhibition, consistent with experiments using EtOH-naïve mice. Rapid tolerance lasts 48 to 96 hours, depending on whether assessing in vitro phase advances or phase delays. Similarly, in vivo, prior EtOH consumption prevented EtOH's acute blockade of photic phase delays. Finally, immunoblot experiments showed no changes in SCN glutamate receptor subunit (NR2B) expression or phosphorylation in response to rapid tolerance induction. CONCLUSIONS: The SCN circadian clock develops rapid tolerance to EtOH as assessed both in vivo and in vitro, and the tolerance lasts for several days. These data demonstrate the utility of the circadian system as a model for investigating cellular mechanisms through which EtOH acts in the brain.

Serotonergic integration of circadian clock and ultradian sleep-wake cycles.

In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus generates a 24 h rhythm of sleep and arousal. While neuronal spiking activity in the SCN provides a functional circadian oscillator that propagates throughout the brain, the ultradian sleep-wake state is regulated by the basal forebrain/preoptic area (BF/POA). How this SCN circadian oscillation is integrated into the shorter sleep-wake cycles remains unclear. We examined the temporal patterns of neuronal activity in these key brain regions in freely behaving rats. Neuronal activity in various brain regions presented diurnal rhythmicity and/or sleep-wake state dependence. We identified a diurnal rhythm in the BF/POA that was selectively degraded when diurnal arousal patterns were disrupted by acute brain serotonin depletion despite robust circadian spiking activity in the SCN. Local blockade of serotonergic transmission in the BF/POA was sufficient to disrupt the diurnal sleep-wake rhythm of mice. These results suggest that the serotonergic system enables the BF/POA to couple the SCN circadian signal to ultradian sleep-wake cycles, thereby providing a potential link between circadian rhythms and psychiatric disorders.

Melatonin ameliorates the sleep disorder induced by surgery under sevoflurane anaesthesia in aged mice.

Post-operative sleep disorders induce adverse effects on patients, especially the elderly, which may be associated with surgery and inhalational anaesthetics. Melatonin is a neuroendocrine regulator of the sleep-wake cycle. In this study, we analysed the alterations of post-operative sleep in aged melatonin-deficient (C57BL/6J) mice, and investigated if exogenous melatonin could facilitate entrainment of circadian rhythm after laparotomy under sevoflurane anaesthesia. The results showed that laparotomy under sevoflurane anaesthesia had a greater influence on post-operative sleep than sevoflurane alone. Laparotomy under anaesthesia led to circadian rhythm shifting forward, altered EEG power density and delta power of NREM sleep, and lengthened REM and NREM sleep latencies. In the light phase, the number of waking episodes tended to decline, and wake episode duration elevated. However, these indicators presented the opposite tendency during the dark phase. Melatonin showed significant efficacy for ameliorating the sleep disorder and restoring physiological sleep, and most of the beneficial effect of melatonin was antagonized by luzindole, a melatonin receptor antagonist.

Dietary Sialyllactose Does Not Influence Measures of Recognition Memory or Diurnal Activity in the Young Pig.

Sialic acid (SA) is an integral component of gangliosides and signaling molecules in the brain and its dietary intake may support cognitive development. We previously reported that feeding sialyllactose, a milk oligosaccharide that contains SA, alters SA content and diffusivity in the pig brain. The present research sought to expand upon such results and describe the effects of feeding sialyllactose on recognition memory and sleep/wake activity using a translational pig model. Pigs were provided ad libitum access to a customized milk replacer containing 0 g/L or 380 g/L of sialyllactose from postnatal day (PND) 2-22. Beginning on PND 15, pigs were fitted with accelerometers to track home-cage activity and testing on the novel object recognition task began at PND 17. There were no significant effects of diet on average daily body weight gain, average daily milk intake, or the gain-to-feed ratio during the study (all p ≥ 0.11). Pigs on both diets were able to display recognition memory on the novel object recognition task (p < 0.01), but performance and exploratory behavior did not differ between groups (all p ≥ 0.11). Total activity and percent time spent sleeping were equivalent between groups during both day and night cycles (all p ≥ 0.56). Dietary sialyllactose did not alter growth performance of young pigs, and there was no evidence that providing SA via sialyllactose benefits the development of recognition memory or gross sleep-related behaviors.

Phase advance is an actimetric correlate of antidepressant response to sleep deprivation and light therapy in bipolar depression.

The combination of total sleep deprivation (TSD) and light therapy (LT) in bipolar depression causes rapid antidepressant effects, and its mechanism of action has been hypothesized to involve the enhancement of all of the monoaminergic systems targeted by antidepressant drugs (serotonin, dopamine, norepinephrine). It is still unknown if the clinical effects are paralleled by changes in biological rhythms. In a before/after design of a study of biological correlates of response, 39 inpatients affected by Type I Bipolar Disorder whose current depressive episode was without psychotic features were treated for one week with repeated TSD combined with morning LT. Wrist actigraphy was recorded throughout the study. Two-thirds of the patients responded to treatment (50% reduction in Hamilton Depression score). Responders showed an increase in daytime activity, phase-advance of the activity-rest rhythm of 57 min compared to the pre-treatment baseline, and reduced nighttime sleep. Non-responders did not show significant changes in the parameters of their activity-rest rhythm. Phase advance of the activity-rest rhythm is an actimetric correlate of the antidepressant response to TSD and LT in bipolar depression. Results are consistent with the known effects of sleep-wake manipulations and neurotransmitter function on the suprachiasmatic nucleus.

Orally administered melatonin improves nocturnal rest in young and old ringdoves (Streptopelia risoria).

Melatonin possesses chronobiotic properties, which affects sleep/wake rhythms. We investigated a 7-day administration of melatonin (0.25, 2.5 and 5 mg/kg body weight) on the activity/rest rhythms of a diurnal animal (the ringdove, Streptopelia risoria), aged 2-3 (young) and 10-12 (old) years, and its possible relationship with the serum levels of melatonin and serotonin. Total nocturnal and diurnal activity pulses were logged at basal, during, and up to 7 days after the treatments. The animals received 0.1 ml of melatonin orally 1 hr before lights off. The results showed that the administration of whichever melatonin dose decreased both diurnal and nocturnal old ringdove activity, the reduction being larger at night. The young animals also reduced their nocturnal activity with all three melatonin concentrations, whereas their diurnal activity only decreased with the 2.5 and 5 mg/kg body weight treatments. We chose those treatments that gave the best results in terms of nocturnal rest and the least affected diurnal activity (0.25 mg/kg body weight and 2.5 mg/kg in the young and old animals, respectively). Serum melatonin was measured by radioimmunoassay and serotonin by ELISA. In both age groups, the treatment increased both nocturnal and diurnal melatonin levels, with the effect continuing until 1 day after the last dose. Serum serotonin levels were unaffected by the treatments in either age group. The treatment restored the amplitude of the serum melatonin rhythm in the old animals to that of the young group. In summary, treatment with melatonin may be appropriate to improve nocturnal rest, and beneficial as a therapy for sleep disorders.

Chronic disruptions of circadian sleep regulation induce specific proinflammatory responses in the rat colon.

Exposure to environmental conditions that disturb the daily rhythms has been shown to enhance the proinflammatory responses of immunostimulant-challenged immune system. However, it is not known whether circadian disturbances may stimulate unchallenged immune responses and thus contribute per se to the development of inflammation-related diseases. Our aim was to ascertain an effect of various conditions threatening the behavioral activity/rest cycle regulation, namely aging with or without melatonin, 6 h advance/delay phase shifts in the light/dark cycle repeated with a 2-day frequency and constant light, on expression of immune markers in the rat colon. The impact of these conditions on parameters of behavioral activity and mRNA levels of selected immune markers in the colonic mucosa of Wistar rats, namely TNFα (Tnf), IL1a (Il1a), IL17RA (Il17ra), STAT3 (Stat3) and Rgs16 (Rsg16), were detected. Our results demonstrate that aging with or without melatonin as well as repeated 6 h advance/delay phase shifts in the light/dark cycle, which increased inactivity as a correlate of sleep during the dark phase of the light/dark cycle (i.e. during the active phase for nocturnal animals), had a minor effect on immune state in the colonic mucosa; all these conditions caused downregulation of gene Rgs16 which is involved in attenuation of the inflammatory response in the colon but did not affect expression of the other immune markers. Interestingly, a long-term absence of melatonin facilitated the aging-induced effect on immune state in the colon. In contrast, exposure to constant light, which perturbed the interval of inactivity (sleep) and led to the complete abolishment of activity/inactivity cycles, activated robustly proinflammatory state in the colon selectively via Stat3-dependent pathway. In spite all these experimental conditions (aging with or without melatonin, shifts in light/dark cycles, constant light) perturbed the activity/rest cycles, none of them induced sleep deprivation. These results provided the first evidence that disruptions in the behavioral activity/inactivity cycles may spontaneously (without immuno-stimulant) induce selective proinflammatory responses in the colonic mucosa. Such effects may take part in the mechanisms of modern lifestyle-induced inflammatory diseases of the gut. ABBREVIATIONS: B2M: ß2-microglobulin; DSS: dextran sodium sulfate; Gapdh: glyceraldehyde-3-phosphate dehydrogenase; Ifng: interferon g; Il1a: interleukin 1a; Il1b: interleukin 1b; Il2: interleukin 2; Il6: interleukin 6; Il17ra: interleukin 17 receptor a; LD: light/dark cycle; LL: constant light; LPS: lipopolysaccharide; Mntr1a: melatonin receptor 1a; PINX: pinealectomy; Rgs16: regulator of G protein signaling 16; RT qPCR: quantitative reverse transcription polymerase chain reaction; Stat3: signal transducer and activator of transcription 3; Th17: type 17 T helper cells; Tnfα: tumor necrosis factor α; Tnfrsf1b: tumor necrosis factor receptor superfamily member 1b.

Improvement of sleep architecture parameters in cirrhotic patients with recurrent hepatic encephalopathy with the use of rifaximin.

BACKGROUND AND AIM: Sleep disorders are frequently reported in patients with cirrhosis and hepatic encephalopathy (HE). This study assessed the effect of rifaximin on sleep architecture parameters in patients with recurrent HE. PATIENTS AND METHODS: This sequential, prospective, and exploratory study involved all patients with cirrhosis and recurrent HE admitted between June 2014 and September 2015. HE was assessed according to the West-Haven Classification. Patients underwent 24-h polysomnography (PSG) and 7-day actigraphy. Rapid eye movement (REM) sleep was considered to be an indicator of good sleep quality. Patients completed questionnaires assessing the quality of sleep and sleepiness. After a 28-day course of rifaximin, the same assessment was repeated. RESULTS: Fifteen patients were included (nine men, mean age: 57±11 years). Child-Pugh scores ranged from B7 to C15. Before rifaximin, the mean HE score was 2.7±0.7. Data from PSG analysis indicated long total sleep time (TST): 571±288 min, and limited REM sleep: 2.5% TST (0-19). Seven-day actigraphy showed an impaired number of steps: 1690/24 h (176-6945). Questionnaires indicated that patients experienced impaired sleep quality and excessive daytime sleepiness. After rifaximin, HE scores decreased to 1.7±0.6 (P<0.001). REM sleep increased to 8.5% TST (0-25) (P=0.003). No changes were observed for TST, number of steps, and on questionnaires. CONCLUSION: Patients with recurrent HE suffer from poor sleep quality and excessive daytime sleepiness. On 24-h PSG, rifaximin improves objective sleep architecture parameters with no changes in the subjective quality of sleep and sleepiness.

Age related changes in the activity-rest circadian rhythms and c-fos expression of ring doves with aging. Effects of tryptophan intake.

Age related changes in the circadian rhythms and sleep quality has been linked with impairment in the function of the suprachiasmatic nucleus (SCN) and melatonin secretion. The precursor of melatonin, serotonin (5-HT) is a neurotransmitter involved in the synchronisation of the circadian clock located in SCN, which shows decreased levels with age. The present work studied the effects of L-tryptophan, the precursor of 5-HT, on the circadian activity-rest rhythm and c-fos expression in the SCN of young and old ring doves, animals diurnal and monocyclic as humans. Two hours before the onset of dark phase, animals housed in cages equipped for activity recording and maintained under 12/12 L/D conditions, received orally L-tryptophan (100 and 240 mg/kg) and, for comparative purposes, melatonin (2.5 and 5 mg/kg). The administration of both L-tryptophan and melatonin reduced the nocturnal activity of all ring doves although only the highest doses were effective in old ones. A reduced amplitude in the activity-rest rhythm was observed in old animals in comparison to youngest, but it was increased after the treatments. Sleep parameters, calculated from the activity data, indicated a worsened sleep quality in old animals but it was improved with the treatments. In addition, the expression of c-fos in the SCN was reduced after both mentioned treatments. The results point to the SCN as a target for the observed nocturnal effects of L-tryptophan and melatonin, and support the supplemental administration of the essential amino acid L-tryptophan to reverse the disturbances of the circadian activity-rest cycle related with ageing.

Adjunctive topiramate in ultradian cycling bipolar disorder: case report with 3-year follow-up.

A patient with a treatment-refractory bipolar disorder with ultradian cycling responded to adjunctive topiramate. Response was maintained during 3-year follow-up.

Contrasting effects of ibotenate lesions of the paraventricular nucleus and subparaventricular zone on sleep-wake cycle and temperature regulation.

The suprachiasmatic nucleus (SCN), the circadian pacemaker for the brain, provides a massive projection to the subparaventricular zone (SPZ), but the role of the SPZ in circadian processes has received little attention. We examined the effects on circadian rhythms of sleep, body temperature, and activity in rats of restricted ibotenic acid lesions of the ventral or dorsal SPZ that spared the immediately adjacent paraventricular hypothalamic nucleus (PVH) and the SCN. Ventral SPZ lesions caused profound reduction of measures of circadian index of sleep (by 90%) and locomotor activity (75% reduction) but had less effect on body temperature (50% reduction); dorsal SPZ lesions caused greater reduction of circadian index of body temperature (by 70%) but had less effect on circadian index of locomotor activity (45% reduction) or sleep (<5% reduction). The loss of circadian regulation of body temperature or sleep was replaced by a strong ultradian rhythm (period approximately 3 hr). Lesions of the PVH, immediately dorsal to the SPZ, had no significant effect on any circadian rhythms that we measured, nor did the lesions affect the baseline body temperature. However, the fever response after intravenous injection of lipopolysaccharide (5 microg/kg) was markedly decreased in the rats with PVH lesions (66.6%) but not dorsal SPZ lesions. These results indicate that circadian rhythms of sleep and body temperatures are regulated by separate neuronal populations in the SPZ, and different aspects of thermoregulation (circadian rhythm and fever response) are controlled by distinct anatomical substrates.

Treatment enhances ultradian rhythms of CSF monoamine metabolites in patients with major depressive episodes.

Unipolar and bipolar depressions show abnormal behavioral manifestations of ultradian (less than 24 h) rhythms, but abnormal rhythms of the central neurotransmitters thought to be important for depression pathophysiology (eg dopamine (DA) and serotonin (5-HT)) have not been shown in this time frame. Since antidepressant treatments normalize disrupted rhythms in depression (eg rapid-eye-movement sleep and hormonal rhythms), we hypothesized that depression-related changes in ultradian oscillations of DA and 5-HT might be revealed during antidepressant treatment. Cerebrospinal fluid (CSF) samples collected q10 min for 24 h in 13 patients experiencing major depressive episodes (MDE) before and after treatment for 5 weeks with sertraline or bupropion were assayed for levels of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA), and their ratio was calculated. Data were analyzed in the frequency domain using Fourier transforms and multivariate permutation testing. Antidepressant treatments were associated with decreased variance for 5-HIAA, increased variance for HVA, and markedly increased variance for the HVA : 5-HIAA ratio (p<0.05, p<0.02, and p<0.003, respectively). With treatment, the correlations between 5-HIAA and HVA weakened (p=0.06). Power spectral density (PSD-the Fourier magnitude squared) of the 5-HIAA signals at periods of 1.75 and 3.7 h (both p<0.05) decreased, while circadian cycling of HVA levels (p<0.05) and of the ratio (p<0.005) increased after treatment. The PSD of the full-length HVA : 5-HIAA ratio series after treatment increased in rapid variability (20-103 min periods, p<0.05). Spectrographic windowing demonstrated a focal span of enhanced HVA : 5-HIAA ratio variability following antidepressant treatment, in an approximately 84-min period through the evening (p<0.05). Periodic neurotransmitter relationships in depressed patients were altered by treatment in this analysis of a small data set. This may represent a baseline abnormality in the regulation of periodic functions involved in the depression pathophysiology, but it could also be due to an unrelated antidepressant effect. Further studies including comparisons with healthy subject data are in progress.

The selective tachykinin neurokinin 1 (NK1) receptor antagonist, GR 205,171, stereospecifically inhibits light-induced phase advances of hamster circadian activity rhythms.

Circadian rhythms in mammals are generated by master pacemaker cells located within the suprachiasmatic nucleus of the hypothalamus. In hamsters, the suprachiasmatic nucleus contains a small collection of cells immunoreactive for substance P, the endogenous ligand of tachykinin neurokinin 1 (NK1) receptors. In addition, two other nuclei which form part of the circadian system, the intergeniculate leaflet of the thalamus and the raphe nuclei, also contain fibers and/or cell bodies immunoreactive for substance P. In light of these observations, we evaluated the influence of the selective tachykinin NK1 receptor antagonist, GR 205,171, upon circadian activity rhythms in the hamster. Systemic injection of GR 205,171 dose-dependently (2.5-40.0 mg/kg, i.p.) inhibited light-induced phase advances in hamster circadian wheel running activity rhythms by approximately 50%. In contrast, GR 226,206, the less active enantiomer of GR 205,171, failed to affect light-induced phase advances. In addition, we examined the potential ability of GR 205,171 to induce non-photic phase shifts in hamster wheel running rhythms when injected at mid-day to late night circadian times. However, GR 205,171 (40 mg/kg) did not elicit non-photic phase shifts at these times indicating that tachykinin NK1 receptor antagonists are only effective when a light stimulus is applied to the pacemaker. Although GR 205,171 may, in theory, activate several sites within the circadian system, we suggest that GR 205,171 acts in the raphe nuclei to increase inhibitory serotonergic input to pacemaker cells in the suprachiasmatic nuclei, thereby suppressing photic modulation of the pacemaker. These findings have important implications for the use of tachykinin NK1 receptor antagonists in the treatment of depression and other central nervous system disorders.

Chronic ethanol intake alters circadian period-responses to brief light pulses in rats.

Although chronic alcohol intake is associated with widespread disruptions of sleep-wake cycles and other daily biological rhythms in both human alcoholics and experimental animals, the extent to which the chronobiological effects of alcohol are mediated by effects on the underlying circadian pacemaker remains unknown. Nevertheless, recent studies indicate that both adult and perinatal ethanol treatments may alter the free-running period and photic responsiveness of the circadian pacemaker. The present experiment was designed to further characterize the effects of chronic ethanol intake on the response of the rat circadian pacemaker to brief light pulses. Ethanol-treated and control animals were exposed to 15-min light pulses during either early or late subjective night on the first day of constant darkness following entrainment to a 12:12 light-dark cycle. Relative to pulses delivered during early subjective night and to "no-pulse" conditions, light pulses delivered during late subjective night resulted in period-shortening after-effects under constant darkness, but only in control animals, not in ethanol-treated animals. These results indicate that chronic ethanol intake reduces the responsiveness of the circadian pacemaker to acute photic stimulation, and suggest that the chronobiological disruptions seen in human alcoholics are due in part to alterations in circadian pacemaker function.

Melatonin and light induce phase shifts of circadian activity rhythms in the C3H/HeN mouse.

This study examines the effect of light pulses and administration of the pineal hormone melatonin on the circadian activity rhythm of C3H/HeN mice. Mice were housed in constant dark in cages equipped with running wheels. Phase shifts in the circadian rhythm of wheel-running activity were measured following treatment with a 15-min pulse of light (300 lux) or administration of vehicle (ethanol/saline) or melatonin (90 micrograms, sc). Light treatment induced phase changes in circadian activity rhythms; specifically, delays during early subjective night (circadian time [CT] 12.5 to CT 18.5) and advances during late subjective night (CT 0.5). A single dose of melatonin administered at various CTs had no consistent effect on free-running circadian activity rhythms. By contrast, melatonin administration for 3 consecutive days at the same clock time induced advances in circadian activity rhythms by more than 1 h when the first dose was administered at CT 10 and induced delays in circadian activity rhythms by up to 1 h when the first dose was administered between CT 24 and CT 2. With the caveat that multi- ple melatonin treatments are required to induce phase shifts, the results suggest that the circadian timing system controlling the rhythm of wheel-running activity in the C3H/HeN mouse is responsive to both light and melatonin.

Circadian rhythms in Neurospora crassa: farnesol or geraniol allow expression of rhythmicity in the otherwise arrhythmic strains frq10, wc-1, and wc-2.

In Neurospora crassa, the circadian rhythm can be seen in the bd (band) strain as a series of "bands" or conidiation (spore-forming) regions on the surface of an agar medium. Certain mutations at 3 different genes (frq, wc-1, or wc-2) lead to the loss of the circadian rhythm. In this study, it was found that the addition of 10(-4) to 10(-5) M of geraniol or farnesol restored rhythmic banding to strains that lack a circadian rhythm due to mutations in any 1 of these 3 genes. These 3 conditionally arrhythmic strains now exhibited robust, free-running conidiation rhythms. Their rhythms were neither temperature-compensated nor obviously sensitive to light, so the full properties of a circadian rhythm were not restored. At 20 degrees C, in growth tubes, farnesol treatment gave periods of 28, 26, and 22 h for the frq10, wc-1, and wc-2 strains, respectively. Geraniol treatment at 20 degrees C gave periods of 23, 25.5, and 24.5 h for the frq10, wc-1, and wc-2 strains, respectively. A PRC for temperature pulses (1 h, 20 to 40 degrees C) for the frq10 strain grown in the presence of geraniol showed strong resetting (type 0), suggesting that a temperature-sensitive oscillator was present. Farnesol and geraniol are related to known intermediates in the steroid (or mevalonate) pathway. These data are interpreted in terms of a 2-oscillator model, in which farnesol/geraniol activate or amplify a remaining oscillator (a postulated frq-less oscillator).