Fabio García-García

Manipulations during forced wakefulness have differential impact on sleep architecture, EEG power spectrum, and Fos induction.

We propose a hypothesis suggesting that the most prominent experiences occurring during wakefulness activate specific clusters of neurons related to such experiences. These neurons could possibly then evoke the release of various types of sleep-inducing molecules, thereby causing different patterns of sleep architecture. In this study, we therefore sought to determine whether manipulations of behavior during wakefulness, such as forced wakefulness induced by gentle handling, forced wakefulness associated with a stressful condition such as immobilization, or forced wakefulness associated with excess intake of palatable food, could result in a variation of Fos immunoreactivity in selective brain structures and could also result in different sleep and EEG power density patterns. The results showed that the sleep-wake cycle of rats after all the experimental manipulations was different not only with respect to the control group but also among themselves. Additionally, power spectrum analysis showed an increase of 0.25-4.0 Hz in all experimental manipulations, whereas the 4.25-8.0 Hz increase occurred only in the situation of forced wakefulness plus stress. The Fos induction showed activation of cell clusters in cortical areas and telencephalic centers, in several hypothalamic nuclei, in monoaminergic cell groups, and in brain stem nuclei. The density of Fos-immunoreactive neurons varied in relation to the different paradigms of forced wakefulness. These results suggest that activation of cell clusters in the brain are related to the type of manipulation imposed on the rat during wakefulness and that such variation in cell activation prior to sleep may be associated with sleep architecture and EEG power.

Sleep deprivation induces differential morphological changes in the hippocampus and prefrontal cortex in young and old rats

Sleep is a fundamental state necessary for maintenance of physical and neurological homeostasis throughout life. Several studies regarding the functions of sleep have been focused on effects of sleep deprivation on synaptic plasticity at a molecular and electrophysiological level, and only a few studies have studied sleep function from a structural perspective. Moreover, during normal aging, sleep architecture displays some changes that could affect normal development in the elderly. In this study, using a Golgi‐Cox staining followed by Sholl analysis, we evaluate the effects of 24 h of total sleep deprivation on neuronal morphology of pyramidal neurons from Layer III of the prefrontal cortex (PFC) and the dorsal hippocampal CA1 region from male Wistar rats at two different ages (3 and 22 months). We found no differences in total dendritic length and branching length in both analyzed regions after sleep deprivation. Spine density was reduced in the CA1 of young‐adults, and interestingly, sleep deprivation increased spine density in PFC of aged animals. Taken together, our results show that 24 h of total sleep deprivation have different effects on synaptic plasticity and could play a beneficial role in cognition during aging. Synapse 69:15–25, 2015.

Growth hormone improves hippocampal adult cell survival and counteracts the inhibitory effect of prolonged sleep deprivation on cell proliferation

Sleep deprivation (SD) produces numerous deleterious changes in brain cells, including apoptosis. It has been demonstrated that growth hormone (GH) stimulates cell growth and counteracts apoptosis, although this anti-apoptotic effect has not been tested against SD. To determine the protective effect of GH administration on cell proliferation and survival in the dentate gyrus (DG) of the hippocampus after sleep deprivation; we injected Wistar adult rats with a low dose of recombinant human GH (rhGH 5 ng/kg) per seven days and then we gently sleep deprived the animals for 48 consecutive hours. 5-Bromodeoxiuridine (BrdU) was administered to assess cell proliferation after the GH treatment and NeuN was used as marker of cell fate. Our results indicate that GH produced a three fold increase in the number of BrdU positive cells within the DG [Control = 1044 ± 106.38 cells, rhGH = 2952 ± 99.84 cells, P<0.01]. In contrast, 48 h of SD significantly reduced cell proliferation but this effect was antagonized by the GH administration [SD = 540 ± 18.3 cells, rhGH + SD = 1116 ± 84.48 cells, P<0.004]. Paradoxically, SD and GH administration increased cell survival separately but no significantly compared with control animals. However, cell survival was increased in animals treated with rhGH+SD compared to rats injected with saline solution [P<0.04]. Within the survival cells, the percentage of neurons was higher in SD animals [95%] compared with saline group, while this percentage (NeuN positive cells) was increased in animals treated with rhGH+SD [120%] compared with rhGH [25%] alone. Our findings indicate that GH strongly promotes cell proliferation in the adult brain and also protects the hippocampal neuronal precursors against the deleterious effect of prolonged sleep loss.

Ghrelin and its interactions with growth hormone, leptin and orexins: implications for the sleep-wake cycle and metabolism

Several studies have shown that ghrelin administration promotes wakefulness in rodents, while in human males it induces sleep but has no effect in women. Ghrelin also plays an important role in metabolism and appetite regulation, and as described in this review may participate in the energy balance during sleep. In this review, we summarize some of the effects induced by ghrelin administration on the sleep-wake cycle in relation to the effects of other hormones, such as growth hormone, leptin, and orexin. Finally we discuss the relationship between sleep deprivation, obesity and ghrelin secretion pattern.

Narcolepsy as an Immune-Mediated Disease

Narcolepsy is a neurological disorder characterized by excessive daytime sleepiness, cataplexy, hypnagonic hallucinations, sleep paralysis, and disturbed nocturnal sleep patterns. This disease is secondary to the specific loss of hypothalamic hypocretin (orexin)-producing neurons in the lateral hypothalamus. An autoimmune basis for the disease has long been suspected based on its strong association with the genetic marker DQB1∗06:02, and current studies greatly support this hypothesis. Narcolepsy with hypocretin deficiency is associated with human leukocyte antigen (HLA) and T cell receptor (TCR) polymorphisms, suggesting that an autoimmune process targets a peptide unique to hypocretin-producing neurons via specific HLA-peptide-TCR interactions. This concept has gained a lot of notoriety after the increase of childhood narcolepsy in 2010 following the 2009 H1N1 pandemic (pH1N1) in China and vaccination with Pandemrix, an adjuvanted H1N1 vaccine that was used in Scandinavia. The surge of narcolepsy cases subsequent to influenza A H1N1 infection and H1N1 vaccination suggests that processes such as molecular mimicry or bystander activation might be crucial for disease development.

Endogenous and exogenous factors on sleep-wake cycle regulation.

A number of theories have proposed the involvement of different brain structures and neurotransmitters in order to explain the regulation of the sleep wake cycle. However, there is no clear consensus as to the mechanisms through which the brain structures and their various neurotransmitters interact to produce theses phases. Perhaps the problem is related to the fact sleep is a very fragile state, easily modified or influenced by a variety of substances or experimental manipulations. In this paper, we describe the evidence of two different groups of factors that induce important changes on the sleep wake cycle. The endogenous factors: neurotransmitters; hormone; peptides; and some substances of lipidic nature and exogenous factors: stress, food intake, learning, sleep deprivation, sensorial stimulation, exercise and temperature on the regulation the sleep-wake cycle. Likewise, we propose a hypothesis which attempts to reconcile the fact that endogenous and exogenous factors have similar effects.

Current and Emerging Options for the Drug Treatment of Narcolepsy

Narcolepsy/hypocretin deficiency (now called type 1 narcolepsy) is a lifelong neurologic disorder with well-established diagnostic criteria and etiology. Narcolepsy is a chronic sleep disorder characterized by excessive daytime sleepiness (EDS) and symptoms of dissociated rapid eye movement sleep such as cataplexy (sudden loss of muscle tone), hypnagogic hallucinations (sensory events that occur at the transition from wakefulness to sleep), sleep paralysis (inability to perform movements upon wakening or sleep onset), and nocturnal sleep disruption. As these symptoms are often disabling, most patients need life-long treatment. The treatment of narcolepsy is well defined, and, traditionally, amphetamine-like stimulants (i.e., dopaminergic release enhancers) have been used for clinical management to improve EDS and sleep attacks, whereas tricyclic antidepressants have been used as anticataplectics. However, treatments have evolved to better-tolerated compounds such as modafinil or armodafinil (for EDS) and adrenergic/serotonergic selective reuptake inhibitors (as anticataplectics). In addition, night-time administration of a short-acting sedative, γ-hydroxybutyrate (sodium oxybate), has been used for the treatment for EDS and cataplexy. These therapies are almost always needed in combination with non-pharmacologic treatments (i.e., behavioral modification). A series of new drugs is currently being tested in animal models and in humans. These include a wide variety of hypocretin agonists, melanin-concentrating hormone receptor antagonists, antigen-specific immunopharmacology, and histamine H3 receptor antagonists/inverse agonists (e.g., pitolisant), which have been proposed for specific therapeutic applications, including the treatment of Alzheimer’s disease, attention-deficit hyperactivity disorder, epilepsy, and more recently, narcolepsy. Even though current treatment is strictly symptomatic, based on the present state of knowledge of the pathophysiology of narcolepsy, we expect that more pathophysiology-based treatments will be available in the near future.

Sleep-Inducing Factors

Kuniomi Ishimori and Henri Piéron were the first researchers to introduce the concept and experimental evidence for a chemical factor that would presumably accumulate in the brain during waking and eventually induce sleep. This substance was named hypnotoxin. Currently, the variety of substances which have been shown to alter sleep includes peptides, cytokines, neurotransmitters and some substances of lipidic nature, many of which are well known for their involvement in other biological activities. In this chapter, we describe the sleep-inducing properties of the vasoactive intestinal peptide, prolactin, adenosine and anandamide.

Brain distribution of vasoactive intestinal peptide receptors following REM sleep deprivation.

Vasoactive intestinal peptide (VIP) has been shown to increase rapid eye movement (REM) sleep in normal and insomniac animals, while the administration of anti-VIP antibodies or an antagonist of VIP receptors decreases REM sleep. In addition, recently, it has been suggested that a VIP-like substance accumulates in the CSF during waking and that it may be involved in the production of the REM rebound normally seen following REM sleep deprivation. This evidence suggests that VIP may be important in modulating REM sleep in normal conditions and during REM sleep rebound. To determine whether VIP is involved in REM sleep homeostasis, VIP receptors of discrete brain areas was determined by autoradiography after 24 and 72 h of REM sleep deprivation (REM SD) by the water tank technique. Since this procedure has been suggested to produce some stress, an additional group adapted for 7 days to the sleep deprivation situation was tested. The results showed that REM SD produces an increase in the density of VIP receptors in several brainstem and forebrain structures at 24 h of REM SD and more so at 72 h of REM SD. Interestingly, results showed that habituation to the REM SD procedure decreases the density of VIP receptors in some areas of the brain of the REM sleep-deprived rats. The results are discussed in terms of the possibility that waking induces an increase of VIP receptors in several structures, which in turn are responsible for modulating REM sleep, but that stress contributes in part to VIP receptor changes.

Detrimental role of prolonged sleep deprivation on adult neurogenesis

Adult mammalian brains continuously generate new neurons, a phenomenon called adult neurogenesis. Both environmental stimuli and endogenous factors are important regulators of adult neurogenesis. Sleep has an important role in normal brain physiology and its disturbance causes very stressful conditions, which disrupt normal brain physiology. Recently, an influence of sleep in adult neurogenesis has been established, mainly based on sleep deprivation studies. This review provides an overview on how rhythms and sleep cycles regulate hippocampal and subventricular zone neurogenesis, discussing some potential underlying mechanisms. In addition, our review highlights some interacting points between sleep and adult neurogenesis in brain function, such as learning, memory, and mood states, and provides some insights on the effects of antidepressants and hypnotic drugs on adult neurogenesis.