Pleasure: The missing link in the regulation of sleep

Mammalian NREM and REM sleep: Why, when and how

This report proposes that fish use the spinal-rhombencephalic regions of their brain to support their activities while awake. Instead, the brainstem-diencephalic regions support the wakefulness in amphibians and reptiles. Lastly, mammals developed the telencephalic cortex to attain the highest degree of wakefulness, the cortical wakefulness. However, a paralyzed form of spinal-rhombencephalic wakefulness remains in mammals in the form of REMS, whose phasic signs are highly efficient in promoting maternal care to mammalian litter. Therefore, the phasic REMS is highly adaptive. However, their importance is low for singletons, in which it is a neutral trait, devoid of adaptive value for adults, and is mal-adaptive for marine mammals. Therefore, they lost it. The spinal-rhombencephalic and cortical wakeful states disregard the homeostasis: animals only attend their most immediate needs: foraging defense and reproduction. However, these activities generate allostatic loads that must be recovered during NREMS, that is a paralyzed form of the amphibian-reptilian subcortical wakefulness. Regarding the regulation of tonic REMS, it depends on a hypothalamic switch. Instead, the phasic REMS depends on an independent proportional pontine control.

The Circadian Molecular Machinery in CNS Cells: A Fine Tuner of Neuronal and Glial Activity With Space/Time Resolution

The circadian molecular machinery is a fine timekeeper with the capacity to harmonize physiological and behavioral processes with the external environment. This tight-knit regulation is coordinated by multiple cellular clocks across the body. In this review, we focus our attention on the molecular mechanisms regulated by the clock in different brain areas and within different cells of the central nervous system. Further, we discuss evidence regarding the role of circadian rhythms in the regulation of neuronal activity and neurotransmitter systems. Not only neurons, but also astrocytes and microglia actively participate in the maintenance of timekeeping within the brain, and the diffusion of circadian information among these cells is fine-tuned by neurotransmitters (e.g., dopamine, serotonin, and γ-aminobutyric acid), thus impacting on the core clock machinery. The bidirectional interplay between neurotransmitters and the circadian clockwork is fundamental in maintaining accuracy and precision in daily timekeeping throughout different brain areas. Deepening the knowledge of these correlations allows us to define the basis of drug interventions to restore circadian rhythms, as well as to predict the onset of drug treatment/side effects that might promote daily desynchronization. Furthermore, it may lead to a deeper understanding of the potential impacts of modulations in rhythmic activities on the pace of aging and provide an insight in to the pathogenesis of psychiatric diseases and neurodegenerative disorders.

The Birth of the Mammalian Sleep

Simple Summary

Mammals evolved from reptiles as a consequence of an evolutionary bottleneck. Some diurnal reptiles extended their activity, first to twilight and then to the entire dark time. This forced the change of the visual system. Pursuing maximal sensitivity, they abandoned the filters protecting the eyes against the dangerous diurnal light, which, in turn, forced immobility in lightproof burrows during light time. This was the birth of the mammalian sleep. Then, the Cretacic-Paleogene extinction of dinosaurs leaved free the diurnal niche and allowed the expansion of a few early mammals to diurnal life and the high variability of sleep traits. On the other hand, we propose that the idling rest is a state showing homeostatic regulation. Therefore, the difference between behavioral rest and wakeful idling is rather low: both show quiescence, raised sensory thresholds, reversibility, specific sleeping-resting sites and body positions, it is a pleasing state, and both are dependent of circadian and homeostatic regulation. Indeed, the most important difference is the unconsciousness of sleep and the consciousness of wakeful idling. Thus, we propose that sleep is a mere upgrade of the wakeful rest, and both may have the same function: guaranteeing rest during a part of the daily cycle.

Abstract

Mammals evolved from small-sized reptiles that developed endothermic metabolism. This allowed filling the nocturnal niche. They traded-off visual acuity for sensitivity but became defenseless against the dangerous daylight. To avoid such danger, they rested with closed eyes in lightproof burrows during light-time. This was the birth of the mammalian sleep, the main finding of this report. Improved audition and olfaction counterweighed the visual impairments and facilitated the cortical development. This process is called “The Nocturnal Evolutionary Bottleneck”. Pre-mammals were nocturnal until the Cretacic-Paleogene extinction of dinosaurs. Some early mammals returned to diurnal activity, and this allowed the high variability in sleeping patterns observed today. The traits of Waking Idleness are almost identical to those of behavioral sleep, including homeostatic regulation. This is another important finding of this report. In summary, behavioral sleep seems to be an upgrade of Waking Idleness Indeed, the trait that never fails to show is quiescence. We conclude that the main function of sleep consists in guaranteeing it during a part of the daily cycle.

Recent advances in the utilization of tea active ingredients to regulate sleep through neuroendocrine pathway, immune system and intestinal microbiota

Sleep disorders have received widespread attention nowadays, which have been promoted by the accelerated pace of life, unhealthy diets and lack of exercise in modern society. The chemical medications to improve sleep has shown serious side effects and risks with high costs. Therefore, it is urgent to develop efficient nutraceuticals from natural sources to ensure sleep quality as a sustainable strategy. As the second most consumed beverage worldwide, the health-promoting effects of tea have long been widely recognized. However, the modulatory effect of teas on sleep disorders has received much less attention. Tea contains various natural sleep-modulating active ingredients such as L-theanine (LTA), caffeine, tea polyphenols (TPP), tea pigments, tea polysaccharides (TPS) and γ-aminobutyric acid (GABA). This review focuses on the potential influence and main regulating mechanisms of different tea active ingredients on sleep, including being absorbed by the small intestine and then cross the blood-brain barrier to act on neurons in the brain as neurotransmitters, manipulating the immune system and further affect sleep-wake cycle by regulating the levels of cytokines, and controlling the gut microbes to maintain the homeostasis of circadian rhythm. Current research progress and limitations are summarized and several future development directions are also proposed. This review hopes to provide new insights into the future elucidation of the sleep-regulating mechanisms of different teas and their natural active ingredients and the development of tea-based functional foods for alleviating sleep disorders. HighlightsNatural sleep-modulating active ingredients in tea have been summarized.Influences of drinking tea or tea active ingredients on sleep are reviewed.Three main regulating mechanisms of tea active ingredients on sleep are explained.The associations among nervous system, immune system and intestinal microbiota are investigated.The potential of developing delivery carriers for tea active ingredients is proposed.

The Property-Based Practical Applications and Solutions of Genetically Encoded Acetylcholine and Monoamine Sensors

Neuromodulatory communication among various neurons and non-neuronal cells mediates myriad physiological and pathologic processes, yet defining regulatory and functional features of neuromodulatory transmission remains challenging because of limitations of available monitoring tools. Recently developed genetically encoded neuromodulatory transmitter sensors, when combined with superresolution and/or deconvolution microscopy, allow the first visualization of neuromodulatory transmission with nanoscale or microscale spatiotemporal resolution. In vitro and in vivo experiments have validated several high-performing sensors to have the qualities necessary for demarcating fundamental synaptic properties of neuromodulatory transmission, and initial analysis has unveiled unexpected fine control and precision of neuromodulation. These new findings underscore the importance of synaptic dynamics in synapse-, subcellular-, and circuit-specific neuromodulation, as well as the prospect of genetically encoded transmitter sensors in expanding our knowledge of various behaviors and diseases, including Alzheimer's disease, sleeping disorders, tumorigenesis, and many others.

Genetically encoded sensors enable micro- and nano-scopic decoding of transmission in healthy and diseased brains

Neural communication orchestrates a variety of behaviors, yet despite impressive effort, delineating transmission properties of neuromodulatory communication remains a daunting task due to limitations of available monitoring tools. Recently developed genetically encoded neurotransmitter sensors, when combined with superresolution and deconvolution microscopic techniques, enable the first micro- and nano-scopic visualization of neuromodulatory transmission. Here we introduce this image analysis method by presenting its biophysical foundation, practical solutions, biological validation, and broad applicability. The presentation illustrates how the method resolves fundamental synaptic properties of neuromodulatory transmission, and the new data unveil unexpected fine control and precision of rodent and human neuromodulation. The findings raise the prospect of rapid advances in the understanding of neuromodulatory transmission essential for resolving the physiology or pathogenesis of various behaviors and diseases.