A variant in orexin receptor-2 is associated with self-reported daytime sleepiness in the Japanese population.

Excessive daytime sleepiness is characterized by a persistent feeling of having trouble staying awake, typically with inappropriate sleep episodes. Orexin (hypocretin) is a neuropeptide that regulates sleep-wake cycles and rapid eye movement sleep. Several large-scale genome-wide association studies (GWASs) in European populations have found genetic variants in orexin receptor-1 (OX1R) and -2 (OX2R) that are associated with sleep traits including daytime sleepiness. To identify genetic variants associated with daytime sleepiness, we performed an association study of genetic variants in prepro-orexin, OX1R, and OX2R in 14,329 Japanese individuals from the Tohoku Medical Megabank Project cohort. A genetic variant in OX2R was significantly associated with self-reported daytime sleepiness after Bonferroni correction (rs188018846: P = 8.4E-05). In addition, a missense variant in OX2R identified by the European GWASs showed a nominally significant association with daytime sleepiness in a Japanese population (p.Ile308Val, rs2653349: P = 0.044). Multiple genetic variants in OX2R can affect daytime sleepiness in general populations.

Oral Administration of Methylphenidate (Ritalin) Affects Dopamine Release Differentially Between the Prefrontal Cortex and Striatum: A Microdialysis Study in the Monkey.

Methylphenidate (MPH; trade name Ritalin) is a widely used drug for the treatment of attention deficit hyperactivity disorder (ADHD) and is often used as a cognitive enhancer. Because MPH increases dopamine (DA) release by blocking the DA transporter in the human striatum, MPH is supposed to work on attention and cognition through a DA increase in the striatum. However, ADHD patients show impaired prefrontal cortex (PFC) function and MPH administration is associated with increased neural activity in the PFC. Although MPH is indicated to increase DA release in the rat PFC, there has been no study to examine MPH-induced DA changes in the human PFC because of technical difficulties associated with the low level of PFC DA receptors. Using the microdialysis technique, we examined the effects of oral administration of MPH on DA release in both the PFC and striatum in the monkey. We also tested the effect of MPH on cognitive task performance. As in human studies, in the striatum, both high and low doses of MPH induced consistent increases in DA release ∼30 min after their administrations. In the PFC, a consistent increase in DA release was observed 1 h after a high dose, but not low doses, of MPH. Low doses of MPH improved cognitive task performance, but a high dose of MPH made the monkey drowsy. Therefore, low-dose MPH-induced cognitive enhancement is supported by striatum DA increase.SIGNIFICANCE STATEMENT Methylphenidate (MPH) is a widely used drug for the treatment of attention deficit hyperactivity disorder and is often used as a cognitive enhancer. Although human positron emission tomography studies suggest that MPH works on attention and cognition through dopamine (DA) changes in the striatum, there has been no study to examine MPH-induced DA changes in the human prefrontal cortex (PFC). Using the microdialysis technique in monkeys, we found, for the first time, that low doses of MPH consistently increased DA release in the striatum but did not in the PFC. Cognitive enhancement effects of low doses of MPH are supposed to be supported by the striatum DA increase.

Hypocretin/orexin loss changes the hypothalamic immune response.

Hypocretin, also known as orexin, maintains the vigilance state and regulates various physiological processes, such as arousal, sleep, food intake, energy expenditure, and reward. Previously, we found that when wild-type mice and hypocretin/ataxin-3 littermates (which are depleted of hypothalamic hypocretin-expressing neurons postnatally) were administered lipopolysaccharide (LPS), the two genotypes exhibited significant differences in their sleep/wake cycle, including differences in the degree of increase in sleep periods and in recovery from sickness behaviour. In the present study, we examined changes in the hypothalamic vigilance system and in the hypothalamic expression of inflammatory factors in response to LPS in hypocretin/ataxin-3 mice. Peripheral immune challenge with LPS affected the hypothalamic immune response and vigilance states. This response was altered by the loss of hypocretin. Hypocretin expression was inhibited after LPS injection in both hypocretin/ataxin-3 mice and their wild-type littermates, but expression was completely abolished only in hypocretin/ataxin-3 mice. Increases in the number of histidine decarboxylase (HDC)-positive cells and in Hdc mRNA expression were found in hypocretin/ataxin-3 mice, and this increase was suppressed by LPS. Hypocretin loss did not impact the change in expression of hypothalamic inflammatory factors in response to LPS, except for interferon gamma and colony stimulating factor 3. The number of c-Fos-positive/HDC-positive cells in hypocretin/ataxin-3 mice administered LPS injections was elevated, even during the rest period, in all areas, suggesting that there is an increase in the activity of histaminergic neurons in hypocretin/ataxin-3 mice following LPS injection. Taken together, our results suggest a novel role for hypocretin in the hypothalamic response to peripheral immune challenge. Our findings contribute to the understanding of the pathophysiology of narcolepsy.

Chronic restraint stress triggers dopaminergic and noradrenergic neurodegeneration: Possible role of chronic stress in the onset of Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and, to a lesser extent, in the noradrenergic neurons of the locus coeruleus (LC). Most cases of PD are idiopathic and sporadic and are believed to be the result of both environmental and genetic factors. Here, to the best of our knowledge, we report the first evidence that chronic restraint stress (8h/day, 5days/week) substantially reduces nigral DA and LC noradrenergic neuronal cell numbers in rats. Loss of DA neurons in the SNpc was evident after 2weeks of stress and progressed in a time-dependent manner, reaching up to 61% at 16weeks. This reduction was accompanied by robust microglial activation and oxidative stress and was marked by nitrotyrosine in the SNpc and LC of the midbrain. These results indicate that chronic stress triggers DA and noradrenergic neurodegeneration by increasing oxidative stress, and that activated microglia in the substantia nigra and LC may play an important role in modulating the neurotoxic effects of oxidative stress. Taken together, these data suggest that exposure to chronic stress triggers DA and noradrenergic neurodegeneration, which is a cause of PD.

Symmetrical serotonin release during asymmetrical slow-wave sleep: implications for the neurochemistry of sleep-waking states.

On land, fur seals predominately display bilaterally synchronized electroencephalogram (EEG) activity during slow-wave sleep (SWS), similar to that observed in all terrestrial mammals. In water, however, fur seals exhibit asymmetric slow-wave sleep (ASWS), resembling the unihemispheric slow-wave sleep of odontocetes (toothed whales). The unique sleeping pattern of fur seals allows us to distinguish neuronal mechanisms mediating EEG changes from those mediating behavioral quiescence. In a prior study we found that cortical acetylcholine release is lateralized during ASWS in the northern fur seal, with greater release in the hemisphere displaying low-voltage (waking) EEG activity, linking acetylcholine release to hemispheric EEG activation (Lapierre et al. 2007). In contrast to acetylcholine, we now report that cortical serotonin release is not lateralized during ASWS. Our data demonstrate that bilaterally symmetric levels of serotonin are compatible with interhemispheric EEG asymmetry in the fur seal. We also find greatly elevated levels during eating and hosing the animals with water, suggesting that serotonin is more closely linked to bilateral variables, such as axial motor and autonomic control, than to the lateralized cortical activation manifested in asymmetrical sleep.

Caffeine promotes glutamate and histamine release in the posterior hypothalamus.

Histamine neurons are active during waking and largely inactive during sleep, with minimal activity during rapid-eye movement (REM) sleep. Caffeine, the most widely used stimulant, causes a significant increase of sleep onset latency in rats and humans. We hypothesized that caffeine increases glutamate release in the posterior hypothalamus (PH) and produces increased activity of wake-active histamine neurons. Using in vivo microdialysis, we collected samples from the PH after caffeine administration in freely behaving rats. HPLC analysis and biosensor measurements showed a significant increase in glutamate levels beginning 30 min after caffeine administration. Glutamate levels remained elevated for at least 140 min. GABA levels did not significantly change over the same time period. Histamine level significantly increased beginning 30 min after caffeine administration and remained elevated for at least 140 min. Immunostaining showed a significantly elevated number of c-Fos-labeled histamine neurons in caffeine-treated rats compared with saline-treated animals. We conclude that increased glutamate levels in the PH activate histamine neurons and contribute to caffeine-induced waking and alertness.

Contribution of default mode network to game and delayed-response task performance: Power and connectivity analyses of theta oscillation in the monkey.

Neuroimaging studies have demonstrated the presence of a default mode network (DMN) which shows greater activity during rest, and an executive network (EN) which is activated during cognitive tasks. DMN and EN are thought to have competing functions. However, recent studies reported that the two networks show coactivation during some cognitive tasks. To clarify how DMN works and how DMN interacts with EN for cognitive control, we recorded EEG activities in the medial prefrontal (anterior DMN: aDMN), posterior cingulate/precuneus (posterior DMN: pDMN), and lateral prefrontal (EN) areas in the monkey. As cognitive tasks, we employed a monkey-monkey competitive video game (GAME) and a delayed-response (DR) task. We focused on theta oscillation because of its importance in cognitive control. We also examined theta band connectivity among the three network areas using the Granger causality analysis. DMN and EN were found to work cooperatively in both tasks. In all the three network areas, we found GAME-task-related, but no DR-task-related, increase in theta power from the resting level, maybe because of the higher cognitive demand associated with the GAME task performance. The information flow conveyed by the theta oscillation was directed more to aDMN than from aDMN for both tasks. The GAME-task-related increase in theta power in aDMN is supposed to be supported by more information flow conveyed by the theta oscillation from EN and pDMN.

Time-course of cerebrospinal fluid histamine in the wake-consolidated squirrel monkey.

Central nervous system (CNS) histamine is low in individuals with narcolepsy, a disease characterized by severe fragmentation of both sleep and wake. We have developed a primate model, the squirrel monkey, with which we can examine the role of the CNS in the wake-consolidation process, as these primates are day-active, have consolidated wake and sleep and have cerebrospinal fluid (CSF) that is readily accessible. Using this model and three distinct protocols, we report herein on the role of CNS histamine in the wake consolidation process. CSF histamine has a robust daily rhythm, with a mean of 24.9 ± 3.29 pg mL(-1) , amplitude of 31.7 ± 6.46 pg mL(-1) and a peak at 17:49 ± 70.3 min (lights on 07:00-19:00 hours). These levels are not significantly affected by increases (up to 161 ± 40.4% of baseline) or decreases (up to 17.2 ± 2.50% of baseline) in locomotion. In direct contrast to the effects of sleep deprivation in non-wake-consolidating mammals, in whom CSF histamine increases, pharmacologically induced sleep (γ-hydroxybutyrate) and wake (modafinil) have no direct effects on CSF histamine concentrations. These data indicate that the time-course of histamine in CSF in the wake-consolidated squirrel monkey is robust against variation in activity and sleep and wake-promoting pharmacological compounds, and may indicate that histamine physiology plays a role in wake-consolidation such as is present in the squirrel monkey and humans.

A rare genetic variant in the cleavage site of prepro-orexin is associated with idiopathic hypersomnia.

Idiopathic hypersomnia (IH) is a rare, heterogeneous sleep disorder characterized by excessive daytime sleepiness. In contrast to narcolepsy type 1, which is a well-defined type of central disorders of hypersomnolence, the etiology of IH is poorly understood. No susceptibility loci associated with IH have been clearly identified, despite the tendency for familial aggregation of IH. We performed a variation screening of the prepro-orexin/hypocretin and orexin receptors genes and an association study for IH in a Japanese population, with replication (598 patients and 9826 controls). We identified a rare missense variant (g.42184347T>C; p.Lys68Arg; rs537376938) in the cleavage site of prepro-orexin that was associated with IH (minor allele frequency of 1.67% in cases versus 0.32% in controls, P = 2.7 × 10-8, odds ratio = 5.36). Two forms of orexin (orexin-A and -B) are generated from cleavage of one precursor peptide, prepro-orexin. The difference in cleavage efficiency between wild-type (Gly-Lys-Arg; GKR) and mutant (Gly-Arg-Arg; GRR) peptides was examined by assays using proprotein convertase subtilisin/kexin (PCSK) type 1 and PCSK type 2. In both PCSK1 and PCSK2 assays, the cleavage efficiency of the mutant peptide was lower than that of the wild-type peptide. We also confirmed that the prepro-orexin peptides themselves transmitted less signaling through orexin receptors than mature orexin-A and orexin-B peptides. These results indicate that a subgroup of IH is associated with decreased orexin signaling, which is believed to be a hallmark of narcolepsy type 1.

Genome-wide association study of idiopathic hypersomnia in a Japanese population.

Idiopathic hypersomnia (IH) is a rare sleep disorder characterized by excessive daytime sleepiness, great difficulty upon awakening, and prolonged sleep time. In contrast to narcolepsy type 1, which is a well-recognized hypersomnia, the etiology of IH remains poorly understood. No susceptibility loci for IH have been identified, although familial aggregations have been observed among patients with IH. Narcolepsy type 1 is strongly associated with human leukocyte antigen (HLA)-DQB1*06:02; however, no significant associations between IH and HLA alleles have been reported. To identify genetic variants that affect susceptibility to IH, we performed a genome-wide association study (GWAS) and two replication studies involving a total of 414 Japanese patients with IH and 6587 healthy Japanese individuals. A meta-analysis of the three studies found no single-nucleotide polymorphisms (SNPs) that reached the genome-wide significance level. However, we identified several candidate SNPs for IH. For instance, a common genetic variant (rs2250870) within an intron of PDE9A was suggestively associated with IH. rs2250870 was significantly associated with expression levels of PDE9A in not only whole blood but also brain tissues. The leading SNP in the PDE9A region was the same in associations with both IH and PDE9A expression. PDE9A is a potential target in the treatment of several brain diseases, such as depression, schizophrenia, and Alzheimer's disease. It will be necessary to examine whether PDE9A inhibitors that have demonstrated effects on neurophysiologic and cognitive function can contribute to the development of new treatments for IH, as higher expression levels of PDE9A were observed with regard to the risk allele of rs2250870. The present study constitutes the first GWAS of genetic variants associated with IH. A larger replication study will be required to confirm these associations. Supplementary Information: The online version contains supplementary material available at 10.1007/s41105-021-00349-2.

Substantia nigra pars reticulata-mediated sleep and motor activity regulation.

STUDY OBJECTIVES: The substantia nigra pars reticulata (SNR) is a major output nucleus of the basal ganglia. Animal studies have shown that lesions of the SNR cause hyposomnia and motor hyperactivity, indicating that the SNR may play a role in the control of sleep and motor activity. METHODS: Eight 8- to 10-week-old adult male Sprague-Dawley rats were used. After 3 days of baseline polysomnographic recording, dialysates were collected from the lateral SNR across natural sleep-wake states. Muscimol and bicuculline were microinfused into the lateral SNR. RESULTS: We found that GABA release in the lateral SNR is negatively correlated with slow wave sleep (SWS; R = -0.266, p < 0.01, n = 240) and positively correlated with waking (R = 0.265, p < 0.01, n = 240) in rats. Microinfusion of muscimol into the lateral SNR decreased sleep time and sleep quality, as well as eliciting motor hyperactivity in wake and increased periodic leg movement in SWS, while bicuculline infused into the lateral SNR increased sleep and decreased motor activity in SWS in rats. Muscimol infusion skewed the distribution of inter-movement intervals, with most between 10 and 20 s, while a flat distribution of intervals between 10 and 90 s was seen in baseline conditions. CONCLUSIONS: Activation of the lateral SNR is important for inducing sleep and inhibiting motor activity prior to and during sleep, and thus to the maintenance of sleep. Abnormal function of the lateral SNR may cause hyposomnia and motor hyperactivity in quiet wake and in sleep.

Behavioral response and transmitter release during atonia elicited by medial medullary stimulation.

Activation of the medial medulla is responsible for rapid eye movement (REM) sleep atonia and cataplexy. Dysfunction can cause REM sleep behavior disorder and other motor pathologies. Here we report the behavioral effects of stimulation of the nucleus gigantocellularis (NGC) and nucleus magnocellularis (NMC) in unrestrained cats. In waking, 62% of the medial medullary stimulation sites suppressed muscle tone. In contrast, stimulation at all sites, including sites where stimulation produced no change or increased muscle tone in waking, produced decreased muscle tone during slow-wave sleep. In the decerebrate cat electrical stimulation of the NGC increased glycine and decreased norepinephrine (NE) release in the lumbar ventral horn, with no change in γ-aminobutyric acid (GABA) or serotonin (5-HT) release. Stimulation of the NMC increased both glycine and GABA release and also decreased both NE and 5-HT release in the ventral horn. Glutamate levels in the ventral horn were not changed by either NGC or NMC stimulation. We conclude that NGC and NMC play neurochemically distinct but synergistic roles in the modulation of motor activity across the sleep-wake cycle via a combination of increased release of glycine and GABA and decreased release of 5-HT and NE. Stimulation of the medial medulla that elicited muscle tone suppression also triggered rapid eye movements, but never produced the phasic twitches that characterize REM sleep, indicating that the twitching and rapid eye movement generators of REM sleep have separate brain stem substrates.

Transcriptional regulation of the hypocretin/orexin gene by NR6A1.

The hypocretin (also known as orexin) neuropeptide system coordinates the regulation of various physiological processes. A reduction in Nr6a1 expression was observed in hypocretin neuron-ablated transgenic mice. To show that prepro-hypocretin transcription is functionally modulated by NR6A1, we performed chromatin immunoprecipitation (ChIP) analysis, double-immunostaining, a luciferase reporter assay, and an in utero electroporation study. ChIP analysis showed that endogenous NR6A1 binds to a putative NR6A1-binding site. Double-immunostaining indicated almost all hypocretin neurons were positive for NR6A1 immunoreactivity. NR6A1 overexpression in SH-SY5Y cells modulated hypocretin promoter activity, an effect that was countered by lacking a putative NR6A1-binding site. Electroporation with Nr6a1 in the foetal hypothalamus promoted hypocretin transcription as compared to GFP-electroporation. These experiments confirmed that NR6A1 works as a regulator for hypocretin transcription.

Metabolome analysis using cerebrospinal fluid from narcolepsy type 1 patients.

Narcolepsy type 1 (NT1) is a hypersomnia characterized by excessive daytime sleepiness and cataplexy. Inappropriate regulation of fatty acid metabolism has been suggested to be involved in the pathophysiology of NT1, but the detailed mechanisms remain uncertain. Here we performed a metabolomic analysis of cerebrospinal fluid samples from 14 NT1 and 17 control subjects using a novel capillary electrophoresis coupled with Fourier transform mass spectrometry. A total of 268 metabolites were identified and the amount of histidine was the most significantly increased in NT1 patients (p = 4.0 × 10-4). Validation analysis using high-performance liquid chromatography (HPLC) including independent replication samples also identified the association of histidine (p = 2.02 × 10-3). Further, levels of histamine, which is synthesized from histidine, were also examined using HPLC and were found to be significantly decreased in NT1 patients (p = 6.12 × 10-4). Pathway analysis with nominally significant metabolites identified several pathways related to the metabolism of glycogenic amino acids, suggesting that glycogenesis is enhanced in NT1 as a compensatory mechanism for fatty acid metabolism. We performed further exploratory analysis, searching for metabolites associated with sleep variables from polysomnography and the multiple sleep latency test. As a result, 5'-deoxy-5'-methylthioadenosine showed a significant association with apnea-hypopnea index (p = 2.66 ×10-6). Moreover, gamma aminobutyric acid displayed a negative correlation with rapid eye movement sleep latency (REML), and thus might represent an intriguing target for future studies to elucidate how the controlling circuit of REM sleep is associated with abnormally short REML in NT1.

A Susceptible Period of Photic Day-Night Rhythm Loss in Common Marmoset Social Behavior Development.

The prevalence of neurodevelopmental psychiatric disorders such as pervasive developmental disorders is rapidly increasing worldwide. Although these developmental disorders are known to be influenced by an individual's genetic background, the potential biological responses to early life's environmental exposure to both physical and psychological factors must also be considered. Many studies have acknowledged the influence of shorter time for rest at night and the simultaneous occurrence of various kinds of complications involving developmental disorders. In a prior study, we examined how a common marmoset's (Callithrix jacchus) psychosocial development was affected when it was reared under constant daylight from birth and then reared individually by humans nursing them under constant light (LL) during their juvenile development stages. The behaviors of these marmosets were compared with those of normal day-night cycle (LD) marmosets using a multivariate analysis based on principal component analysis (PCA). That study found that LL marmosets relatively elicited egg-like calls (Ecall) and side-to-side shakes of the upper body with rapid head rotation through adulthood frequently. Based on the PCA, these behaviors were interpreted as "alert" or "hyperactive" states. However, we did not clarify susceptible periods of the photic rhythm loss experience and the psychological development output. In this study we summarize the following studies in our model animal colonies involving 30 animals (11 female, 19 males) to further explore critical age states of inquiry about each social behavior profiling. We compared social behaviors of three age stages, juvenile, adolescent and young adult equivalent to one another in four LL experience conditions, LL (postnatal day (P) 0 to around 150), Middle (P60-149, 90 days), Late (P150-239, 90 days), and LD (no experience). In the most representative 1st and 2nd principal component scores, the shifting to higher frequency of alert behaviors developed at the adult stage in LL, Middle, then Late in turn. The no LL experience group, LD, generally featured higher frequency of local preference of high position compared to LL experience present groups, in adulthood. This limited model primate study might inspire different developmental age sensitive mechanisms of neuronal network to control socio-emotional functions by utilizing the multivariate visualization method, BOUQUET. This study could potentially contribute to nurturing educational designs for social developmental disorders.

Intracellular ATP levels in mouse cortical excitatory neurons varies with sleep-wake states.

Whilst the brain is assumed to exert homeostatic functions to keep the cellular energy status constant under physiological conditions, this has not been experimentally proven. Here, we conducted in vivo optical recordings of intracellular concentration of adenosine 5'-triphosphate (ATP), the major cellular energy metabolite, using a genetically encoded sensor in the mouse brain. We demonstrate that intracellular ATP levels in cortical excitatory neurons fluctuate in a cortex-wide manner depending on the sleep-wake states, correlating with arousal. Interestingly, ATP levels profoundly decreased during rapid eye movement sleep, suggesting a negative energy balance in neurons despite a simultaneous increase in cerebral hemodynamics for energy supply. The reduction in intracellular ATP was also observed in response to local electrical stimulation for neuronal activation, whereas the hemodynamics were simultaneously enhanced. These observations indicate that cerebral energy metabolism may not always meet neuronal energy demands, consequently resulting in physiological fluctuations of intracellular ATP levels in neurons.

CSF histamine contents in narcolepsy, idiopathic hypersomnia and obstructive sleep apnea syndrome.

STUDY OBJECTIVE: To (1) replicate our prior result of low cerebrospinal fluid (CSF) histamine levels in human narcolepsy in a different sample population and to (2) evaluate if histamine contents are altered in other types of hypersomnia with and without hypocretin deficiency. DESIGN: Cross sectional studies. SETTING AND PATIENTS: Sixty-seven narcolepsy subjects, 26 idiopathic hypersomnia (IHS) subjects, 16 obstructive sleep apnea syndrome (OSAS) subjects, and 73 neurological controls were included. All patients were Japanese. Diagnoses were made according to ICSD-2. RESULTS: We found significant reductions in CSF histamine levels in hypocretin deficient narcolepsy with cataplexy (mean +/- SEM; 176.0 +/- 25.8 pg/mL), hypocretin non-deficient narcolepsy with cataplexy (97.8 +/- 38.4 pg/mL), hypocretin non-deficient narcolepsy without cataplexy (113.6 +/- 16.4 pg/mL), and idiopathic hypersomnia (161.0 +/- 29.3 pg/ mL); the levels in OSAS (259.3 +/- 46.6 pg/mL) did not statistically differ from those in the controls (333.8 +/- 22.0 pg/mL). Low CSF histamine levels were mostly observed in non-medicated patients; significant reductions in histamine levels were evident in non-medicated patients with hypocretin deficient narcolepsy with cataplexy (112.1 +/- 16.3 pg/ mL) and idiopathic hypersomnia (143.3 +/- 28.8 pg/mL), while the levels in the medicated patients were in the normal range. CONCLUSION: The study confirmed reduced CSF histamine levels in hypocretin-deficient narcolepsy with cataplexy. Similar degrees of reduction were also observed in hypocretin non-deficient narcolepsy and in idiopathic hypersomnia, while those in OSAS (non central nervous system hypersomnia) were not altered. The decrease in histamine in these subjects were more specifically observed in non-medicated subjects, suggesting CSF histamine is a biomarker reflecting the degree of hypersomnia of central origin.

The Effects of Frankincense Essential Oil on Stress in Rats.

Frankincense essential oil, obtained from Boswellia carteri, is a popular essential oil, which is widely used in many parts of the world. While some of its properties are known, its effects on stress and sleep have not been studied. The effects of frankincense essential oil and its major components, limonene and α-pinene, on plasma corticosterone and glutathione (GSH) levels, as well as on sleep and wakefulness behaviour, were studied in sleep-deprived rats. The substances were applied topically after dilution in jojoba oil (vehicle). As compared to vehicle, frankincense essential oil at a dilution of 1/1000 (1:103) significantly reduced corticosterone levels (p < 0.05). In contrast, its major constituents (α-pinene and limonene), elevated levels of this stress hormone. Frankincense, limonene and α-pinene, all led to significant reductions in plasma GSH levels. Although frankincense dose-dependently reduced plasma concentrations of antioxidant ions albeit to levels insufficient to neutralize oxidative stress; levels of products of oxidative metabolism metabolites were decreased by the frankincense. In sleep-deprived rats, frankincense 1:103 respectively increased and decreased the amount of wakefulness and non-rapid eye movement sleep. Frankincense essential oil can counter the effects of stress by effectively relieving sleep debt and maintaining antioxidant capacity without increasing oxidative stress, and, therefore, may be beneficial in the management of stress.

In situ estimation of optical properties of rat and monkey brains using femtosecond time-resolved measurements.

An accurate knowledge of tissue optical properties (absorption coefficients, µa, and reduced scattering coefficients, µs') is critical for precise modeling of light propagation in biological tissue, essential for developing diagnostic and therapeutic optical techniques that utilize diffusive photons. A great number of studies have explored the optical properties of various tissue, and these values are not known in detail due to difficulties in the experimental determination and significant variations in tissue constitution. Especially, in situ estimates of the optical properties of brain tissue, a common measurement target in optical imaging, is a challenge because of its layer structure (where the thin gray matter covers the white matter). Here, we report an approach to in situ estimates of the µa and µs' of the gray and white matter in living rat and monkey brains by using femtosecond time-resolved measurements and Monte Carlo simulation. The results demonstrate that the µa of the gray matter is larger than that of the white matter, while there was no significant difference in the µs' between the gray and white matter. The optical properties of the rat brain were very similar to those of the monkey brain except for the µa of the gray matter here.