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suprachiasmatic nucleus

Minou Nirvani, Cuong Khuu, Tor Paaske Utheim, Lars Peter Sand, Amer Sehic
The circadian clock is comprised of a master component situated in the hypothalamic suprachiasmatic nucleus and subordinate clock genes in almost every cell of the body. The circadian clock genes and their encoded proteins govern the organism to follow the natural signals of time, and adapt to external changes in the environment. The majority of physiological processes in mammals exhibit variable circadian rhythms, which are generated and coordinated by an oscillation in the expression of the clock genes. A number of studies have reported that alteration in the expression level of clock genes is correlated with several pathological conditions, including cancer...
February 2018: Molecular and Clinical Oncology
Juan Cheng, Xu Huang, Yue Liang, Tian Xue, Liecheng Wang, Jin Bao
Neurons in the suprachiasmatic nucleus (SCN) exhibit circadian variation in their neuronal activities. Here, we show that their input synapses undergo daily regulation. We discovered daily variation in the frequencies, but not the peak amplitudes, of miniature postsynaptic currents (mPSCs) for both glutamatergic and GABAergic synapses. In addition, the changes in the frequencies of mPSCs from glutamatergic and GABAergic synapses were antiphasic: An increase in the glutamatergic mPSC frequency and a decrease in the GABAergic mPSC frequency co-occurred during the dark phase of the light-dark cycle...
February 2018: Journal of Biological Rhythms
Claire Gizowski, Cristian Zaelzer, Charles W Bourque
Previous studies have shown that mice housed under 12:12 h light-dark conditions display a pronounced increase in water intake during a 2-hour anticipatory period (AP) near the end of their active period (Zeitgeber Time ZT; ZT21.5-ZT23.5) compared to the preceding basal period (BP, ZT19.5-ZT21.5). This increased water intake during the AP is not associated with physiological stimuli for thirst, such as food intake, hyperosmolality, hyperthermia, or hypovolemia. Denying mice the water intake supplement during the AP causes them to be dehydrated at wake time...
February 5, 2018: Journal of Neuroendocrinology
Mia Y Bothwell, Martha U Gillette
Oxidation-reduction reactions are essential to life as the core mechanisms of energy transfer. A large body of evidence in recent years presents an extensive and complex network of interactions between the circadian and cellular redox systems. Recent advances show that cellular redox state undergoes a ~24-h (circadian) oscillation in most tissues and is conserved across the domains of life. In nucleated cells, the metabolic oscillation is dependent upon the circadian transcription-translation machinery and, vice versa, redox-active proteins and cofactors feed back into the molecular oscillator...
February 2, 2018: Free Radical Biology & Medicine
Yuko Ikeda, Mayo Kamagata, Mizuho Hirao, Shinnosuke Yasuda, Shiho Iwami, Hiroyuki Sasaki, Miku Tsubosaka, Yuta Hattori, Ai Todoh, Konomi Tamura, Kazuto Shiga, Teiji Ohtsu, Shigenobu Shibata
The circadian system controls the behavior and multiple physiological functions. In mammals, the suprachiasmatic nucleus (SCN) acts as the master pacemaker and regulates the circadian clocks of peripheral tissues. The SCN receives information regarding the light-dark cycle and is thus synchronized to the external 24-hour environment. In contrast, peripheral clocks, such as the liver clock, receive information from the SCN and other factors; in particular, food intake which leads to insulin secretion induces strong entrainment of the liver clock...
January 26, 2018: EBioMedicine
Asadur Rahman, Arif Ul Hasan, Akira Nishiyama, Hiroyuki Kobori
The morning surge in blood pressure (BP) coincides with increased cardiovascular (CV) events. This strongly suggests that an altered circadian rhythm of BP plays a crucial role in the development of CV disease (CVD). A disrupted circadian rhythm of BP, such as the non-dipping type of hypertension (i.e., absence of nocturnal BP decline), is frequently observed in metabolic disorders and chronic kidney disease (CKD). The circadian timing system, controlled by the central clock in the suprachiasmatic nucleus of the hypothalamus and/or by peripheral clocks in the heart, vasculature, and kidneys, modulates the 24 h oscillation of BP...
January 30, 2018: International Journal of Molecular Sciences
Kelin Wheaton, Sydney Aten, Lucas Sales Queiroz, Kyle Sullivan, John Oberdick, Kari R Hoyt, Karl Obrietan
The circadian timing system influences the functional properties of most, if not all, physiological processes. Central to the mammalian timing system is the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN functions as a 'master clock' that sets the phasing of ancillary circadian oscillator populations found throughout the body. Further, via an entraining input from the retina, the SCN ensures that the clock oscillators are synchronized to the daily light/dark cycle. A critical component of the SCN timing and entrainment systems is the p44/42 mitogen-activated protein kinase (ERK/MAPK) pathway...
January 31, 2018: European Journal of Neuroscience
Jessica A Krizo, Linley E Moreland, Ashutosh Rastogi, Xiang Mou, Rebecca A Prosser, Eric M Mintz
BACKGROUND: Circadian rhythms of physiology and behavior are driven by a circadian clock located in the suprachiasmatic nucleus of the hypothalamus. This clock is synchronized to environmental day/night cycles by photic input, which is dependent on the presence of mature brain-derived neurotrophic factor (BDNF) in the SCN. Mature BDNF is produced by the enzyme plasmin, which is converted from plasminogen by the enzyme tissue-type plasminogen activator (tPA). In this study, we evaluate circadian function in mice lacking functional tPA...
January 25, 2018: BMC Physiology
Ariadna Amador, Theodore M Kamenecka, Laura A Solt, Thomas P Burris
Circadian signaling regulates and synchronizes physiological and behavioral processes, such as feeding, metabolism, and sleep cycles. The endogenous molecular machinery that regulates circadian activities is located in the suprachiasmatic nucleus of the hypothalamus. The REV-ERBs are transcription factors that play key roles in the regulation of the circadian clock and metabolism. Using pharmacological methods, we recently demonstrated the involvement of the REV-ERBs in sleep architecture. Another group reported a delayed response to sleep deprivation and altered sleep cycles in REV-ERBα null mice, indicating a role of REV-ERBα in sleep...
January 17, 2018: Biochemical Pharmacology
I Herichová, K Hasáková, D Lukáčová, B Mravec, Ľ Horváthová, D Kavická
The effects of food reward on circadian system function were investigated in the hypothalamic nuclei, prefrontal cortex and liver. Food rewards of small hedonic and caloric value were provided for 16 days 3 h after light phase onset to male Wistar rats. The daily pattern of locomotor activity was monitored. Gene expression profiling performed in the dorsomedial hypothalamus (DMH) and liver at the time of reward delivery indicated transcriptional factors egr1 and npas2 as possible mediators of food reward effects...
December 30, 2017: Physiological Research
J Myslivecek, V Farar, P Valuskova
M(4) muscarinic receptors (M(4) MR) represent a subfamily of G-protein coupled receptors serving a substantial role in spontaneous locomotor activity regulation, cognition and modulation of cholinergic system. With increasing body of literature discussing the role of M(4) MR some controversies arose. Thus, we try here to summarize the current evidence regarding the M(4) MR, with the special focus on their role in Locomotor activity control. We review the molecular function of M(4) MR in specific brain areas implicated in locomotor regulation, and shortly in other CNS processes that could be connected to locomotor activity...
December 30, 2017: Physiological Research
Changgui Gu, Huijie Yang, Man Wang
Living beings on the Earth are subjected to and entrained (synchronized) to the natural 24-h light-dark cycle. Interestingly, they can also be entrained to an external artificial cycle of non-24-h periods. The range of these periods is called the entrainment range and it differs among species. In mammals, the entrainment range is regulated by a main clock located in the suprachiasmatic nucleus (SCN) which is composed of 10 000 neurons in the brain. Previous works have found that the entrainment range depends on the cellular coupling strength in the SCN...
November 2017: Physical Review. E
Roberto Paganelli, Claudia Petrarca, Mario Di Gioacchino
The 2017 Nobel Prize for Physiology or Medicine, awarded for the discoveries made in the past 15 years on the genetic and molecular mechanisms regulating many physiological functions, has renewed the attention to the importance of circadian rhythms. These originate from a central pacemaker in the suprachiasmatic nucleus in the brain, photoentrained via direct connection with melanopsin containing, intrinsically light-sensitive retinal ganglion cells, and it projects to periphery, thus creating an inner circadian rhythm...
2018: Clinical and Molecular Allergy: CMA
Mitsugu Sujino, Takeshi Asakawa, Mamoru Nagano, Satoshi Koinuma, Koh-Hei Masumoto, Yasufumi Shigeyoshi
In mammals, the principal circadian oscillator exists in the hypothalamic suprachiasmatic nucleus (SCN). In the SCN, CLOCK works as an essential component of molecular circadian oscillation, and ClockΔ19 mutant mice show unique characteristics of circadian rhythms such as extended free running periods, amplitude attenuation, and high-magnitude phase-resetting responses. Here we investigated what modifications occur in the spatiotemporal organization of clock gene expression in the SCN of ClockΔ19 mutants...
January 16, 2018: Scientific Reports
Shigenobu Shibata, Akiko Furutani
Circadian clock system has been widely maintained in many spices from prokaryote to mammals. "Circadian" means "approximately day" in Latin, thus circadian rhythm means about 24 hour rhythms. The earth revolves once every 24 hours, and our circadian system has been developed for adjusting to this 24 hour cycles, to get sun light information for getting their foods or for alive in birds or mammals. We have two different circadian systems so-called main oscillator located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and local oscillator located in the various peripheral organ tissues such as liver, kidney and skeletal muscle...
2018: Nihon Yakurigaku Zasshi. Folia Pharmacologica Japonica
Bao-Jun Guo, Si-Yi Yu, Zhi-Fu Shen, You-Ping Hu
OBJECTIVE: To investigate the influence and mechanism of acupuncture at the points in Heel Vessel for the circadian clock genes of Period (Per) 1 and Per 2 mRNAs in the suprachiasmatic nucleus (SCN) in insomnia rats. METHODS: Thirty male SD rats were randomly divided into blank, model, acupuncture groups, 10 rats in each group. Insomnia model was established by intraperitoneal injection of PCPA (suspension, 1 mL/100 g). Acupuncture at "Shenmai" (BL 62) and "Zhaohai" (KI 6) was used in the acupuncture group for continuous 7 days, 15 min/day and once daily...
December 25, 2017: Zhen Ci Yan Jiu, Acupuncture Research
Leila Maria Guissoni Campos, Rogerio Leone Buchaim, Nathani Cristina da Silva, Caio Sergio Galina Spilla, Alessandre Hataka, Luciana Pinato
OBJECTIVE: The clock genes Period (per) 1 and 2 are essential components in the generation and adjustment of biological circadian rhythms by the suprachiasmatic nucleus (SCN). Both genes are also rhythmically present in extrahypothalamic areas such as the hippocampus and cerebellum, considered subordinate oscillators. Several pathological conditions alter rhythmic biological phenomena, but the mechanisms behind these changes involving the clock genes are not well defined. The current study investigated changes in PER1 and PER2 immunoreactivity in the SCN, hippocampus, and cerebellum in a neuroinflammation model...
January 5, 2018: Neuroimmunomodulation
Koliane Ouk, Juliet Aungier, Marc Cuesta, A Jennifer Morton
Circadian abnormalities seen in Huntington's disease (HD) patients are recapitulated in several HD transgenic mouse models. In mice, alongside the master clock located in the suprachiasmatic nucleus (SCN), two other oscillators may influence circadian behaviour. These are the food-entrainable oscillator (FEO) and the methamphetamine-sensitive circadian oscillator (MASCO). SCN- and MASCO- (but not FEO-) driven rhythms are progressively disrupted in the R6/2 mouse model of HD. MASCO-driven rhythms are induced by chronic treatment with low dose of methamphetamine and characterised by an increase in period length to greater than 24 h...
December 21, 2017: Neuropharmacology
Min Yue, Yu Yang, Gai Li Guo, Xi Ming Qin
The circadian clocks are vital to many organisms for their survival and adaption to the surrounding environment. More and more people are interested in the circadian clock and related researches. One of the key characteristics of this endogenous clock is its periodicity. Mechanisms underlying the mammalian circadian rhythms with ~24 h periodicity involve interlocked transcriptional and translational feedback loops. The circadian clock system in mammals consists of hierarchical structures, with the suprachiasmatic nucleus (SCN) as the central pacemaker and peripheral oscillators in other organs...
December 20, 2017: Yi Chuan, Hereditas
Stephanie L Grillo, Salvatore L Stella
Retinal ganglion cells (RGCs) that express the photopigment melanopsin (mRGCs) are photosensitive and initiate the non-image-forming pathway, where the majority of their axons terminate in the suprachiasmatic nucleus (SCN). RGCs only make up approximately half of the cells in the ganglion cell layer of the retina; therefore, it is important to be able to distinguish them from other cell types. The transgenic Thy-1 YFP mouse line 16 (Thy-1 YFP-16) expresses yellow-fluorescent protein (YFP) in projection neurons, including RGCs...
January 17, 2018: Neuroreport
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