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https://www.readbyqxmd.com/read/28505726/entrainment-range-of-the-suprachiasmatic-nucleus-affected-by-the-difference-in-the-neuronal-amplitudes-between-the-light-sensitive-and-light-insensitive-regions
#1
Changgui Gu, Huijie Yang, Zhongyuan Ruan
Mammals not only can be synchronized to the natural 24-h light-dark cycle, but also to a cycle with a non-24-h period. The range of the period of the external cycle, for which the animals can be entrained to, is called the entrainment range, which differs among species. The entrainment range as a characteristic of the animal is determined by the main circadian clock, i.e., the suprachiasmatic nucleus (SCN) in the brain. The SCN is composed of ∼10000 heterogeneous neurons, which can be divided into two subgroups, i...
April 2017: Physical Review. E
https://www.readbyqxmd.com/read/28502923/g-protein-coupled-receptor-signaling-through-gpr176-gz-and-rgs16-tunes-time-in-the-center-of-the-circadian-clock-review
#2
Kaoru Goto, Masao Doi, Tianyu Wang, Sumihiro Kunisue, Iori Murai, Hitoshi Okamura
G-protein-coupled receptors (GPCRs) constitute an immensely important class of drug targets with diverse clinical applications. There are still more than 120 orphan GPCRs whose cognate ligands and physiological functions are not known. A set of circadian pacemaker neurons that governs daily rhythms in behavior and physiology resides in the suprachiasmatic nucleus (SCN) in the brain. Malfunction of the circadian clock has been linked to a multitude of diseases, such as sleeping disorders, obesity, diabetes, cardiovascular diseases, and cancer, which makes the clock an attractive target for drug development...
May 13, 2017: Endocrine Journal
https://www.readbyqxmd.com/read/28484984/the-central-clock-controls-the-daily-rhythm-of-aqp5-expression-in-salivary-glands
#3
Hitoshi Uchida, Takahiro J Nakamura, Nana N Takasu, Aya Obana-Koshino, Hitomi Ono, Takeshi Todo, Takayoshi Sakai, Wataru Nakamura
Salivary secretion displays day-night variations that are controlled by the circadian clock. The central clock in the suprachiasmatic nucleus (SCN) regulates daily physiological rhythms by prompting peripheral oscillators to adjust to changing environments. Aquaporin 5 (Aqp5) is known to play a key role in salivary secretion, but the association between Aqp5 and the circadian rhythm is poorly understood. The aim of our study was to evaluate whether Aqp5 expression in submandibular glands (SMGs) is driven by the central clock in the SCN or by autonomous oscillations...
May 8, 2017: Journal of Physiological Sciences: JPS
https://www.readbyqxmd.com/read/28470123/carbachol-induces-phase-dependent-phase-shifts-of-per1-transcription-rhythms-in-cultured-suprachiasmatic-nucleus-slices
#4
Kumiko Dojo, Yoshiaki Yamaguchi, Jean-Michel Fustin, Masao Doi, Masaki Kobayashi, Hitoshi Okamura
Among nonphotic stimulants, a classic cholinergic agonist, carbachol, is known to have a strong and unique phase-resetting effect on the circadian clock: Intracerebroventricular carbachol treatment causes phase delays during the subjective early night and phase advances in the subjective late night, but the effects of this drug on the suprachiasmatic nucleus (SCN) in vivo and in vitro are still controversial. In the present study, we succeeded in reproducing the biphasic phase-shifting effect of carbachol on clock gene expression in organotypic SCN slices prepared from mice carrying a Per1-promoter fused luciferase gene ( Per1-luc)...
April 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28469414/the-synergistic-role-of-light-feeding-phase-relations-on-entraining-robust-circadian-rhythms-in-the-periphery
#5
Seul-A Bae, Ioannis P Androulakis
The feeding and fasting cycles are strong behavioral signals that entrain biological rhythms of the periphery. The feeding rhythms synchronize the activities of the metabolic organs, such as liver, synergistically with the light/dark cycle primarily entraining the suprachiasmatic nucleus. The likely phase misalignment between the feeding rhythms and the light/dark cycles appears to induce circadian disruptions leading to multiple physiological abnormalities motivating the need to investigate the mechanisms behind joint light-feeding circadian entrainment of peripheral tissues...
2017: Gene Regulation and Systems Biology
https://www.readbyqxmd.com/read/28469105/long-term-levodopa-treatment-accelerates-the-circadian-rhythm-dysfunction-in-a-6-hydroxydopamine-rat-model-of-parkinson-s-disease
#6
Si-Yue Li, Ya-Li Wang, Wen-Wen Liu, Dong-Jun Lyu, Fen Wang, Cheng-Jie Mao, Ya-Ping Yang, Li-Fang Hu, Chun-Feng Liu
BACKGROUND: Parkinson's disease (PD) patients with long-term levodopa (L-DOPA) treatment are suffering from severe circadian dysfunction. However, it is hard to distinguish that the circadian disturbance in patients is due to the disease progression itself, or is affected by L-DOPA replacement therapy. This study was to investigate the role of L-DOPA on the circadian dysfunction in a rat model of PD. METHODS: The rat model of PD was constructed by a bilateral striatal injection with 6-hydroxydopamine (6-OHDA), followed by administration of saline or 25 mg/kg L-DOPA for 21 consecutive days...
May 5, 2017: Chinese Medical Journal
https://www.readbyqxmd.com/read/28466071/temporal-regulation-of-gabaa-receptor-subunit-expression-role-in-synaptic-and-extrasynaptic-communication-in-the-suprachiasmatic-nucleus
#7
James C Walton, John K McNeill, Khallyl A Oliver, H Elliott Albers
Recent molecular studies suggest that the expression levels of δ and γ2 GABAA receptor (GABAAR) subunits regulate the balance between synaptic and extrasynaptic GABA neurotransmission in multiple brain regions. We investigated the expression of GABAAδ and GABAAγ2 and the functional significance of a change in balance between these subunits in a robust local GABA network contained within the suprachiasmatic nucleus of the hypothalamus (SCN). Muscimol, which can activate both synaptic and extrasynaptic GABAARs, injected into the SCN during the day phase advanced the circadian pacemaker, whereas injection of the extrasynaptic GABAA superagonist 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol (THIP) had no effect on circadian phase...
March 2017: ENeuro
https://www.readbyqxmd.com/read/28465284/development-of-diabetes-does-not-alter-behavioral-and-molecular-circadian-rhythms-in-a-transgenic-rat-model-of-type-2-diabetes-mellitus
#8
Jingyi Qian, Anthony P Thomas, Analyne M Schroeder, Kuntol Rakshit, Christopher S Colwell, Aleksey V Matveyenko
Metabolic state and circadian clock function exhibit complex bidirectional relationship. Circadian disruption increases propensity for metabolic dysfunction, whereas common metabolic disorders such as obesity and Type 2 diabetes (T2DM) are associated with impaired circadian rhythms. Specifically, alterations in glucose availability and glucose metabolism have been shown to modulate clock gene expression and function in vitro; however to date it is unknown whether development of diabetes imparts deleterious effects on the suprachiasmatic nucleus (SCN) circadian clock and SCN-driven outputs in vivo...
May 2, 2017: American Journal of Physiology. Endocrinology and Metabolism
https://www.readbyqxmd.com/read/28461004/disruption-of-normal-circadian-clock-function-in-a-mouse-model-of-tauopathy
#9
Korey Stevanovic, Amara Yunus, Aurelie Joly-Amado, Marcia Gordon, David Morgan, Danielle Gulick, Joshua Gamsby
Disruption of normal circadian rhythm physiology is associated with neurodegenerative disease, which can lead to symptoms such as altered sleep cycles. In Alzheimer's disease (AD), circadian dysfunction has been attributed to β-amyloidosis. However, it is unclear whether tauopathy, another AD-associated neuropathology, can disrupt the circadian clock. We have evaluated the status of the circadian clock in a mouse model of tauopathy (Tg4510). Tg4510 mice display a long free-running period at an age when tauopathy is present, and show evidence of tauopathy in the suprachiasmatic nucleus (SCN) of the hypothalamus - the site of the master circadian clock...
April 28, 2017: Experimental Neurology
https://www.readbyqxmd.com/read/28452286/clock-gene-expression-in-the-suprachiasmatic-nucleus-of-hibernating-arctic-ground-squirrels
#10
Tomoko Ikeno, Cory T Williams, C Loren Buck, Brian M Barnes, Lily Yan
Most organisms have a circadian system, entrained to daily light-dark cycles, that regulates 24-h rhythms of physiology and behavior. It is unclear, however, how circadian systems function in animals that exhibit seasonal metabolic suppression, particularly when this coincides with the long-term absence of a day-night cycle. The arctic ground squirrel, Urocytellus parryii, is a medium-sized, semi-fossorial rodent that appears above-ground daily during its short active season in spring and summer before re-entering a constantly dark burrow for 6 to 9 months of hibernation...
April 1, 2017: Journal of Biological Rhythms
https://www.readbyqxmd.com/read/28430522/impact-of-naturalistic-lighting-on-hospitalized-stroke-patients-in-a-rehabilitation-unit-design-and-measurement
#11
Anders West, Poul Jennum, Sofie Amalie Simonsen, Birgit Sander, Milena Pavlova, Helle K Iversen
INTRODUCTION AND RATIONALE: Stroke is a major cause of acquired cerebral disability among adults, frequently accompanied by depression, anxiety, cognitive impairment, disrupted sleep and fatigue. New ways of intervention to prevent these complications are therefore needed. The major circadian regulator, the suprachiasmatic nucleus, is mainly controlled by natural daylight, and the blue spectrum is considered the most powerful. During stroke rehabilitation, patients typically are mostly indoors and therefore not exposed to the natural daytime variation in light intensity...
April 21, 2017: Chronobiology International
https://www.readbyqxmd.com/read/28425198/the-cell-adhesion-molecule-epha4-is-involved-in-circadian-clock-functions
#12
Silke Kiessling, Emma K O'Callaghan, Marlène Freyburger, Nicolas Cermakian, Valérie Mongrain
Circadian (~24 h) rhythms of cellular network plasticity in the central circadian clock, the suprachiasmatic nucleus (SCN), have been described. The neuronal network in the SCN regulates photic resetting of the circadian clock as well as stability of the circadian system during both entrained and constant conditions. EphA4, a cell adhesion molecule regulating synaptic plasticity by controlling connections of neurons and astrocytes, is expressed in the SCN. To address whether EphA4 plays a role in circadian photoreception and influences the neuronal network of the SCN, we have analysed circadian wheel-running behavior of EphA4 knockout (EphA4(-/-) ) mice under different light conditions and upon photic resetting, as well as their light-induced protein response in the SCN...
April 20, 2017: Genes, Brain, and Behavior
https://www.readbyqxmd.com/read/28423315/mir-132-212-modulates-seasonal-adaptation-and-dendritic-morphology-of-the-central-circadian-clock
#13
Lucia Mendoza-Viveros, Cheng-Kang Chiang, Jonathan L K Ong, Sara Hegazi, Arthur H Cheng, Pascale Bouchard-Cannon, Michael Fana, Christopher Lowden, Peng Zhang, Béatrice Bothorel, Matthew G Michniewicz, Stephen T Magill, Melissa M Holmes, Richard H Goodman, Valérie Simonneaux, Daniel Figeys, Hai-Ying M Cheng
The central circadian pacemaker, the suprachiasmatic nucleus (SCN), encodes day length information by mechanisms that are not well understood. Here, we report that genetic ablation of miR-132/212 alters entrainment to different day lengths and non-24 hr day-night cycles, as well as photoperiodic regulation of Period2 expression in the SCN. SCN neurons from miR-132/212-deficient mice have significantly reduced dendritic spine density, along with altered methyl CpG-binding protein (MeCP2) rhythms. In Syrian hamsters, a model seasonal rodent, day length regulates spine density on SCN neurons in a melatonin-independent manner, as well as expression of miR-132, miR-212, and their direct target, MeCP2...
April 18, 2017: Cell Reports
https://www.readbyqxmd.com/read/28423013/mapping-the-co-localization-of-the-circadian-proteins-per2-and-bmal1-with-enkephalin-and-substance-p-throughout-the-rodent-forebrain
#14
Ariana Frederick, Jory Goldsmith, Nuria de Zavalia, Shimon Amir
Despite rhythmic expression of clock genes being found throughout the central nervous system, very little is known about their function outside of the suprachiasmatic nucleus. Determining the pattern of clock gene expression across neuronal subpopulations is a key step in understanding their regulation and how they may influence the functions of various brain structures. Using immunofluorescence and confocal microscopy, we quantified the co-expression of the clock proteins BMAL1 and PER2 with two neuropeptides, Substance P (SubP) and Enkephalin (Enk), expressed in distinct neuronal populations throughout the forebrain...
2017: PloS One
https://www.readbyqxmd.com/read/28416676/dissociation-of-per1-and-bmal1-circadian-rhythms-in-the-suprachiasmatic-nucleus-in-parallel-with-behavioral-outputs
#15
Daisuke Ono, Sato Honma, Yoshihiro Nakajima, Shigeru Kuroda, Ryosuke Enoki, Ken-Ichi Honma
The temporal order of physiology and behavior in mammals is primarily regulated by the circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). Taking advantage of bioluminescence reporters, we monitored the circadian rhythms of the expression of clock genes Per1 and Bmal1 in the SCN of freely moving mice and found that the rate of phase shifts induced by a single light pulse was different in the two rhythms. The Per1-luc rhythm was phase-delayed instantaneously by the light presented at the subjective evening in parallel with the activity onset of behavioral rhythm, whereas the Bmal1-ELuc rhythm was phase-delayed gradually, similar to the activity offset...
May 2, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28415286/dissociation-between-two-subgroups-of-the-suprachiasmatic-nucleus-affected-by-the-number-of-damped-oscillated-neurons
#16
Changgui Gu, Huijie Yang, Jos Ht Rohling
In mammals, the main clock located in the suprachiasmatic nucleus (SCN) of the brain synchronizes the body rhythms to the environmental light-dark cycle. The SCN is composed of about 2×10^{4} neurons which can be classified into three oscillatory phenotypes: self-sustained oscillators, damped oscillators, and arrhythmic neurons. Exposed to an artificial external light-dark cycle with a period of 22h instead of 24h, two subgroups of the SCN can become desynchronized (dissociated). The ventrolateral (VL) subgroup receives photic input and is entrained to the external cycle and a dorsomedial (DM) subgroup oscillates with its endogenous (i...
March 2017: Physical Review. E
https://www.readbyqxmd.com/read/28402052/vasopressin-casts-light-on-the-suprachiasmatic-nucleus
#17
Takahiro Tsuji, Andrew J Allchorne, Meng Zhang, Chiharu Tsuji, Vicky A Tobin, Rafael Pineda, Androniki Raftogianni, Javier E Stern, Valery Grinevich, Gareth Leng, Mike Ludwig
KEY POINTS: A subpopulation of retinal ganglion cells expresses the neuropeptide vasopressin. These retinal ganglion cells project predominately to our biological clock, the suprachiasmatic nucleus (SCN). Light-induced vasopressin release enhances the responses of SCN neurons to light. It also enhances expression of genes involved in photo-entrainment of biological rhythms. ABSTRACT: In all animals, the transition between night and day engages a host of physiological and behavioural rhythms...
April 12, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28401917/cooperative-roles-of-the-suprachiasmatic-nucleus-central-clock-and-the-adrenal-clock-in-controlling-circadian-glucocorticoid-rhythm
#18
Sooyoung Chung, Eun Jeong Lee, Hyo Kyeong Cha, Jeongah Kim, Doyeon Kim, Gi Hoon Son, Kyungjin Kim
The mammalian circadian timing system consists of the central clock in the hypothalamic suprachiasmatic nucleus (SCN) and subsidiary peripheral clocks in other tissues. Glucocorticoids (GCs) are adrenal steroid hormones with widespread physiological effects that undergo daily oscillations. We previously demonstrated that the adrenal peripheral clock plays a pivotal role in circadian GC rhythm by driving cyclic GC biosynthesis. Here, we show that the daily rhythm in circulating GC levels is controlled by bimodal actions of central and adrenal clockwork...
April 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28390292/functional-connectivity-of-the-circadian-clock-and-neural-substrates-of-sleep-wake-disturbance-in-delirium
#19
Sunghyon Kyeong, Soo-Hee Choi, Jung Eun Shin, Woo Suk Lee, Kyu Hyun Yang, Tae-Sub Chung, Jae-Jin Kim
A possible mechanism of disrupted circadian rhythms in delirium was identified using resting-state functional connectivity. Thirty-four delirious patients and 38 non-delirious controls were scanned for resting-state functional MRI. Seed-based connectivity of the suprachiasmatic nucleus was compared between the groups. In delirious patients functional connectivity from the circadian clock was increased to the dorsal anterior cingulate cortex and decreased to the posterior cingulate cortex, parahippocampal gyrus, cerebellum, and thalamus...
April 4, 2017: Psychiatry Research
https://www.readbyqxmd.com/read/28377630/katp-channels-mediate-differential-metabolic-responses-to-glucose-shortage-of-the-dorsomedial-and-ventrolateral-oscillators-in-the-central-clock
#20
Jyh-Jeen Yang, Ruo-Ciao Cheng, Pi-Cheng Cheng, Yi-Chi Wang, Rong-Chi Huang
The suprachiasmatic nucleus (SCN) central clock comprises two coupled oscillators, with light entraining the retinorecipient vasoactive intestinal peptide (VIP)-positive ventrolateral oscillator, which then entrains the arginine vasopressin (AVP)-positive dorsomedial oscillator. While glucose availability is known to alter photic entrainment, it is unclear how the SCN neurones respond to metabolic regulation and whether the two oscillators respond differently. Here we show that the ATP-sensitive K(+) (KATP) channel mediates differential responses to glucose shortage of the two oscillators...
April 4, 2017: Scientific Reports
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