Six-hour selective REM sleep deprivation increases the expression of the galanin gene in the hypothalamus of rats

Chaperone Hsp70 (HSPA1) Is Involved in the Molecular Mechanisms of Sleep Cycle Integration

The molecular mechanisms of sleep cycle integration at the beginning and the end of the inactive period are not clear. Sleep cycles with a predominance of deep slow-wave sleep (SWS) seem to be associated with accelerated protein synthesis in the brain. The inducible Hsp70 chaperone corrects protein conformational changes and has protective properties. This research explores (1) whether the Hspa1 gene encoding Hsp70 protein activates during the daily rapid-eye-movement sleep (REMS) maximum, and (2) whether a lower daily deep SWS maximum affects the Hspa1 expression level during the subsequent REMS. Combining polysomnography in male Wistar rats, RT-qPCR, and Western blotting, we reveal a three-fold Hspa1 upregulation in the nucleus reticularis pontis oralis, which regulates REMS. Hspa1 expression increases during the daily REMS maximum, 5–7 h after the natural peak of deep SWS. Using short-term selective REMS deprivation, we demonstrate that REMS rebound after deprivation exceeds the natural daily maximum, but it is not accompanied by Hspa1 upregulation. The results suggest that a high proportion of deep SWS, usually observed after sleep onset, is a necessary condition for Hspa1 upregulation during subsequent REMS. The data obtained can inform the understanding of the molecular mechanisms integrating SWS and REMS and key biological function(s) of sleep.

The Pituitary-Adrenal Response to Paradoxical Sleep Deprivation Is Similar to a Psychological Stressor, Whereas the Hypothalamic Response Is Unique

Stressors of different natures induce activation of the hypothalamic-pituitary-adrenal (HPA) axis at different magnitudes. Moreover, the HPA axis response to repeated exposure is usually distinct from that elicited by a single session. Paradoxical sleep deprivation (PSD) augments ACTH and corticosterone (CORT) levels, but the nature of this stimulus is not yet defined. The purpose of the present study was to qualitatively compare the stress response of animals submitted to PSD to that of rats exposed once or four times to cold, as a physiological stress, movement restraint (RST) as a mixed stressor and predator odour (PRED) as the psychological stressor, whilst animals were submitted for 1 or 4 days to PSD and respective control groups. None of the stressors altered corticotropin releasing factor immunoreactivity in the paraventricular nucleus of the hypothalamus (PVN), median eminence (ME) or central amygdala, compared to control groups, whereas vasopressin immunoreactivity in PSD animals was decreased in the PVN and increased in the ME, indicating augmented activity of this system. ACTH levels were higher after repeated stress or prolonged PSD than after single- or 1 day-exposure and control groups, whereas the CORT response was habituated by repeated stress, but not by 4-days PSD. This dissociation resulted in changes in the CORT : ACTH ratio, with repeated cold and RST decreasing the ratio compared to single exposure, but no change was seen in PRED and PSD groups. Comparing the magnitude and pattern of pituitary-adrenal response to the different stressors, PSD-induced responses were closer to that shown by PRED-exposed rats. In contrast, the hypothalamic response of PSD-exposed rats was unique, inasmuch as this was the only stressor which increased the activity of the vasopressin system. In conclusion, we propose that the pituitary-adrenal response to PSD is similar to that induced by a psychological stressor.

Major dietary patterns in relation to obesity and quality of sleep among female university students

BACKGROUND

Few studies reported the association of dietary patterns with obesity, central adiposity, and quality of sleep. We aimed to investigate the association between major dietary patterns and anthropometric indices in relation to obesity and quality of sleep among female students of Ahvaz Jundishapur University of Medical Sciences (AJUMS).

METHODS

This cross-sectional study was conducted on 245 female university students aged 18-38 years. To assess sleep quality, we used a self-reported Pittsburgh sleep quality index (PSQI). Usual dietary intakes were assessed with the use of a 168 items food frequency questionnaire (FFQ). We used factor analysis to identify dietary patterns.

RESULTS

Four major dietary patterns were identified: mixed, high protein, Western, and healthy dietary patterns. After adjustment for energy intake, subjects in the upper tertile of the mixed dietary pattern were more likely to have a high quality of sleep than those in the first tertile (odds ratio [OR]: 0.27; 95% CI: 0.13, 0.55). Individuals with greater adherence to Western dietary pattern had greater odds of having low quality of sleep compared to those in the first tertile (OR: 1.99; 95% CI: 1.04, 3.82). A healthy dietary pattern was associated with a higher quality of sleep; however, the association was no longer significant after adjustment for dietary energy intake. No significant association was found for high protein dietary patterns. Compared to the first tertile of the healthy dietary pattern, individuals in the upper tertile were less likely to be centrally obese (OR = 0.15; 95% CI = 0.50-0.52). Participants in the last tertile of the high protein dietary pattern were less likely to be generally obese (OR = 0.34; 95% CI = 0.12-0.99), whereas those in the upper tertile of the Western dietary pattern were more likely to be generally obese (OR = 1.84; 95% CI = 1.08-4.93).

CONCLUSIONS

Adherence to a mixed dietary pattern was associated with a high quality of sleep; however, the result was not significant for a high protein dietary pattern. While the high protein dietary pattern was negatively associated with general and central obesity, students in the upper tertile of the Western dietary pattern were more likely to be generally obese.

Sleep Deprivation Related Changes of Plasma Oxytocin in Males and Female Contraceptive Users Depend on Sex and Correlate Differentially With Anxiety and Pain Hypersensitivity

Disturbed sleep is known to substantially aggravate both the pain condition and the affective state of pain patients. The neurobiological mechanisms underlying these adverse effects are unknown. Oxytocin (OT), being largely involved in social and emotional behavior, is considered to also play a modulatory role in nociception. We hypothesized a pathophysiological role of OT for the hyperalgesic and anxiogenic effects of sleep loss. An established human model of one night of total sleep deprivation (TSD) was used to test this hypothesis. Twenty young healthy students (n = 10 male and n = 10 female) were investigated in a balanced cross-over design, contrasting TSD with a night of habitual sleep (HS). All females took monophasic oral contraceptives (OC) and were investigated during their ‘pill-free’ phase. Plasma OT concentrations were correlated with (1) pain thresholds, (2) descending pain inhibition, and (3) state-anxiety scores. Compared to the HS condition, the plasma OT concentration was significantly increased in sleep deprived females (p = 0.02) but not males (p = 0.69). TSD resulted in pain hypersensitivity to noxious cold (p = 0.05), noxious heat (p = 0.023), and pricking stimuli (p = 0.013) and significantly increased state-anxiety (p = 0.021). While, independent of sex, lower heat pain thresholds correlated with higher plasma OT (p = 0.036), no such associations were found for cold/mechanical pain. In sleep-deprived females, higher plasma OT showed a mild (but insignificant) association with lower pain inhibition (p = 0.093). We found a positive correlation between anxiety-scores and OT (p = 0.021), which was enhanced when respecting “sex” (p = 0.008) and “sleep” (p = 0.001) in a hierarchical regression analysis. Altogether, our study revealed a complex and partially sex-dependent correlation between plasma OT and TSD-induced changes of experimental pain and anxiety. The minor role of OT for TSD-induced changes of evoked pain, and its major involvement in anxiety, argues against a specific role of OT for linking the adverse effects of TSD on pain sensitivity and anxiety with each other. Future investigations are needed in order to dissect out the effect of OC on the sex-dependent effects of TSD observed in our study.

Effects of changes in energy homeostasis and exposure of noxious insults on the expression of orexin (hypocretin) and its receptors in the brain

This review summarizes data regarding the brain expression of the orexin (hypocretin) system including: prepro-orexin (PPO), orexin A (OxA), orexin B (OxB) and the two orexin receptors 1 and 2 (OxR1, OxR2). Clinical data is limited to OxA and OxB in cerebral spinal fluid and serum/plasma, thus necessitating the development of animal models to undertake mechanistic studies. We focus on changes in animal models that were either exposed to a regime of altered sleep, metabolic energy homeostasis, exposed to drugs and noxious insults. Many more expressional studies are available for PPO, OxA and OxB levels, compared to studies of the receptors. Interestingly, the direction and pattern of change for PPO, OxA and OxB is inconsistent amongst studies, whereas for the receptors, there tends to be increased expression for both OxR1 and OxR2 after alterations in energy homeostasis, and an increased expression after noxious insults or exposure to some drugs. The clinical implications of these results from animal models are discussed in light of the findings from human studies, and future research directions are suggested to fill knowledge gaps with regard to the orexin system, particularly during early brain development.

Tuberal hypothalamic neurons secreting the satiety molecule Nesfatin-1 are critically involved in paradoxical (REM) sleep homeostasis

The recently discovered Nesfatin-1 plays a role in appetite regulation as a satiety factor through hypothalamic leptin-independent mechanisms. Nesfatin-1 is co-expressed with Melanin-Concentrating Hormone (MCH) in neurons from the tuberal hypothalamic area (THA) which are recruited during sleep states, especially paradoxical sleep (PS). To help decipher the contribution of this contingent of THA neurons to sleep regulatory mechanisms, we thus investigated in rats whether the co-factor Nesfatin-1 is also endowed with sleep-modulating properties. Here, we found that the disruption of the brain Nesfatin-1 signaling achieved by icv administration of Nesfatin-1 antiserum or antisense against the nucleobindin2 (NUCB2) prohormone suppressed PS with little, if any alteration of slow wave sleep (SWS). Further, the infusion of Nesfatin-1 antiserum after a selective PS deprivation, designed for elevating PS needs, severely prevented the ensuing expected PS recovery. Strengthening these pharmacological data, we finally demonstrated by using c-Fos as an index of neuronal activation that the recruitment of Nesfatin-1-immunoreactive neurons within THA is positively correlated to PS but not to SWS amounts experienced by rats prior to sacrifice. In conclusion, this work supports a functional contribution of the Nesfatin-1 signaling, operated by THA neurons, to PS regulatory mechanisms. We propose that these neurons, likely releasing MCH as a synergistic factor, constitute an appropriate lever by which the hypothalamus may integrate endogenous signals to adapt the ultradian rhythm and maintenance of PS in a manner dictated by homeostatic needs. This could be done through the inhibition of downstream targets comprised primarily of the local hypothalamic wake-active orexin- and histamine-containing neurons.

Ten putative contributors to the obesity epidemic

The obesity epidemic is a global issue and shows no signs of abating, while the cause of this epidemic remains unclear. Marketing practices of energy-dense foods and institutionally-driven declines in physical activity are the alleged perpetrators for the epidemic, despite a lack of solid evidence to demonstrate their causal role. While both may contribute to obesity, we call attention to their unquestioned dominance in program funding and public efforts to reduce obesity, and propose several alternative putative contributors that would benefit from equal consideration and attention. Evidence for microorganisms, epigenetics, increasing maternal age, greater fecundity among people with higher adiposity, assortative mating, sleep debt, endocrine disruptors, pharmaceutical iatrogenesis, reduction in variability of ambient temperatures, and intrauterine and intergenerational effects as contributing factors to the obesity epidemic are reviewed herein. While the evidence is strong for some contributors such as pharmaceutical-induced weight gain, it is still emerging for other reviewed factors. Considering the role of such putative etiological factors of obesity may lead to comprehensive, cause specific, and effective strategies for prevention and treatment of this global epidemic.

Neuropeptides as possible targets in sleep disorders

Insomnia and hypersomnia are frequent sleep disorders, and they are most often treated pharmacologically with hypnotics and wake-promoting compounds. These compounds act on classical neurotransmitter systems, such as benzodiazepines on GABA-A receptors, and amfetamine-like stimulants on monoaminergic terminals to modulate neurotransmission. In addition, acetylcholine, amino acids, lipids and proteins (cytokines) and peptides, are known to significantly modulate sleep and are, therefore, possibly involved in the pathophysiology of some sleep disorders. Due to the recent developments of molecular biological techniques, many neuropeptides have been newly identified, and some are found to significantly modulate sleep. It was also discovered that the impairment of the hypocretin/orexin neurotransmission (a recently isolated hypothalamic neuropeptide system) is the major pathophysiology of narcolepsy, and hypocretin replacement therapy is anticipated to treat the disease in humans. In this article, the authors briefly review the history of neuropeptide research, followed by the sleep modulatory effects of various neuropeptides. Finally, general strategies for the pharmacological therapeutics targeting the peptidergic systems for sleep disorders are discussed.

Selective rapid eye movement sleep deprivation impairs the maintenance of long-term potentiation in the rat hippocampus

Rapid eye movement (REM) sleep deprivation (RSD) is known to impair learning and memory. Previous studies have demonstrated that RSD induces an impairment of hippocampal long-term potentiation (LTP). In most of these studies, RSD was set up prior to LTP induction. In this work, we focused on RSD after LTP induction. We investigated the effect of RSD for 24-48 h after induction of LTP in the dentate gyrus on LTP maintenance and whether a REM rebound after 48 h RSD affected LTP. RSD rats were deprived of REM sleep by stroking their backs using a brush, whereas control rats were allowed to sleep freely. Another control group of rats was awoken during non-REM sleep (NRS) under the same conditions (NRS group). REM-deprived rats displayed a faster decay of population spike amplitudes compared with the control and NRS groups over a 24-h recording time. After 48 h RSD, there was no difference in the population spike amplitudes before or after 4 h of release from RSD. These results suggest that REM sleep after LTP induction in the dentate gyrus plays an essential role in LTP maintenance, whereas a REM rebound does not restore the RSD-induced impairment of LTP.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Opposite effects of sleep rebound on orexin OX1 and OX2 receptor expression in rat brain

Orexins (hypocretins) have been implicated in the regulation of the normal sleep-wake cycle, in sensorimotor programming, and in other homeostatic and neuroregulatory processes. The present study examined the effects of sleep deprivation (SD) and sleep recovery on the expression of orexin 1 receptors (OX1R) and orexin 2 receptors (OX2R) throughout the brain. Rats were sacrificed either immediately after 96 h of sleep deprivation (SD group) or after SD followed by 24 h of sleep recovery (Rebound group). Prepro-orexin mRNA showed a non-significant increase in the SD group relative to controls, but a pronounced and significant increase in the Rebound group (+88%, P < 0.007). Similarly, sleep deprivation produced no effect on OX1R or OX2R mRNA levels. However, in the Rebound group, OX1R mRNA levels increased significantly, compared to either control or SD groups, in 37 of 92 brain regions analyzed, with particularly strong effects in the amygdala and hypothalamus. Changes in OX2R mRNA levels were also seen only in the sleep Rebound group, but they were fewer in number (10 out of 86 regions), were in the direction of decreased rather than increased expression, and were predominantly confined to cerebral cortical areas. These observations indicate that some factor associated with sleep recovery, possibly the compensatory increase in REM sleep, has strong effects on the orexin system at the mRNA level. They further indicate that,pOX1 and OX2 receptors are affected in opposite way and that the former are more vulnerable to these effects than the latter.

A role for galanin in antidepressant actions with a focus on the dorsal raphe nucleus

Selective serotonin reuptake inhibitors, such as fluoxetine (FLX), are the most commonly used drugs in the treatment of major depression. However, there is a limited understanding of their molecular mechanism of action. Although the acute effect of selective serotonin reuptake inhibitors in elevating synaptic serotonin concentrations is well known, the clinical amelioration of depressive symptoms requires 14-21 days of treatment, suggesting that numerous other rearrangements of function in the CNS must take place. In the present study, we demonstrated that 14 days of FLX treatment up-regulated galanin mRNA levels by 100% and GalR2-binding sites by 50%, in the rat dorsal raphe nucleus, where galanin coexists with serotonin. Furthermore, a galanin receptor antagonist, M40, attenuated the antidepressant-like effect of FLX in the forced swim test, a rodent preclinical screen commonly used to evaluate antidepressant-like efficacy. Direct activation of galanin receptors by a galanin receptor agonist, galnon, was found to produce an antidepressant-like effect in the same task. Two other antidepressant treatments also affected the galaninergic system in the monoaminergic nuclei: Electroconvulsive shock elevated galanin mRNA levels in dorsal raphe nucleus, whereas sleep deprivation increased galanin mRNA levels in the locus coeruleus, further underlining the connection between activation of the galaninergic system and antidepressant action of various clinically proven treatments.