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Serotonin and circadian rhythms
Pontes, André Luiz Bezerra de;Engelberth, Rovena Clara Galv?o Januário;Nascimento, Jr., Expedito da Silva;Cavalcante, Judney Cley;Costa, Miriam Stela Maris de Oliveira;Pinato, Luciana;Toledo, Claudio Antonio Barbosa de;Cavalcante, Jeferson de Souza;
Psychology & Neuroscience , 2010, DOI: 10.3922/j.psns.2010.2.011
Abstract: all mammal behaviors and functions exhibit synchronization with environmental rhythms. this is accomplished through an internal mechanism that generates and modulates biological rhythms. the circadian timing system, responsible for this process, is formed by connected neural structures. pathways receive and transmit environmental cues to the central oscillator, the hypothalamic suprachiasmatic nucleus, which mediates physiological and behavioral alterations. the suprachiasmatic nucleus has three major inputs: the retinohypothalamic tract (a direct projection from the retina), the geniculohypothalamic tract (an indirect photic projection originating in the intergeniculate leaflet), and a dense serotonergic plexus from the raphe nuclei. the serotonergic pathway, a source of non-photic cues to the suprachiasmatic nucleus, modulates its activity. the importance of raphe nuclei in circadian rhythms, especially in photic responses, has been demonstrated in many studies. serotonin is the raphe neurotransmitter that triggers phase shifts, inhibits light-induced phase-shifts, and plays a role in controlling the sleep-wake cycle. all data to date have demonstrated the importance of the raphe, through serotonergic afferents, in adjusting circadian rhythms and must therefore be considered a component of the circadian timing system. the aim of this paper is to review the literature addressing the involvement of serotonin in the modulation of circadian rhythm.
Serotonin and circadian rhythms
André Luiz Bezerra de Pontes,Rovena Clara Galv?o Januário Engelberth,Expedito da Silva Nascimento Jr.,Judney Cley Cavalcante
Psychology & Neuroscience , 2010,
Abstract: All mammal behaviors and functions exhibit synchronization with environmental rhythms. This is accomplished through an internal mechanism that generates and modulates biological rhythms. The circadian timing system, responsible for this process, is formed by connected neural structures. Pathways receive and transmit environmental cues to the central oscillator, the hypothalamic suprachiasmatic nucleus, which mediates physiological and behavioral alterations. The suprachiasmatic nucleus has three major inputs: the retinohypothalamic tract (a direct projection from the retina), the geniculohypothalamic tract (an indirect photic projection originating in the intergeniculate leaflet), and a dense serotonergic plexus from the raphe nuclei. The serotonergic pathway, a source of non-photic cues to the suprachiasmatic nucleus, modulates its activity. The importance of raphe nuclei in circadian rhythms, especially in photic responses, has been demonstrated in many studies. Serotonin is the raphe neurotransmitter that triggers phase shifts, inhibits light-induced phase-shifts, and plays a role in controlling the sleep-wake cycle. All data to date have demonstrated the importance of the raphe, through serotonergic afferents, in adjusting circadian rhythms and must therefore be considered a component of the circadian timing system. The aim of this paper is to review the literature addressing the involvement of serotonin in the modulation of circadian rhythm.
Circadian Rhythms and Obesity in Mammals  [PDF]
Oren Froy
ISRN Obesity , 2012, DOI: 10.5402/2012/437198
Abstract: Obesity has become a serious public health problem and a major risk factor for the development of illnesses, such as insulin resistance and hypertension. Attempts to understand the causes of obesity and develop new therapeutic strategies have mostly focused on caloric intake and energy expenditure. Recent studies have shown that the circadian clock controls energy homeostasis by regulating the circadian expression and/or activity of enzymes, hormones, and transport systems involved in metabolism. Moreover, disruption of circadian rhythms leads to obesity and metabolic disorders. Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. Feeding regimens, such as restricted feeding (RF), calorie restriction (CR), and intermittent fasting (IF), provide a time cue and reset the circadian clock and lead to better health. In contrast, high-fat (HF) diet leads to disrupted circadian expression of metabolic factors and obesity. This paper focuses on circadian rhythms and their link to obesity. 1. Introduction Obesity has become a serious and growing public health problem [1]. Attempts to develop new therapeutic strategies have mostly focused on energy expenditure and caloric intake. Recent studies link energy homeostasis to the circadian clock at the behavioral, physiological, and molecular levels [2–5], emphasizing that certain nutrients and the timing of food intake may play a significant role in weight gain [6]. Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. 2. Circadian Rhythms Our planet revolves around its axis causing light and dark cycles of 24 hours. Organisms on our planet evolved to predict these cycles by developing an endogenous circadian (circa: about and dies: day) clock, which is synchronized to external time cues. This way, organisms ensure that physiological processes are carried out at the right time of the circadian cycle [7]. All aspects of physiology, including sleep-wake cycles, cardiovascular activity, endocrine system, body temperature, renal activity, gastrointestinal tract motility, and metabolism, are influenced by the circadian clock [7, 8]. Indeed, 10–20% of all cellular transcripts are cyclically expressed, most of which are tissue-specific [2, 9–13]. 3. The Circadian Clock The central circadian clock is located in the suprachiasmatic nuclei (SCN) of the brain anterior hypothalamus. The SCN clock is composed of multiple, single-cell oscillators synchronized to generate circadian rhythms [8, 14–16]. The
Vection Is Unaffected by Circadian Rhythms  [PDF]
Masaki Ogawa, Hiroshi Ito, Takeharu Seno
Psychology (PSYCH) , 2015, DOI: 10.4236/psych.2015.64041
Abstract: We examined the effect of circadian rhythms on self-motion perception (vection). We measured the strength of vection (i.e. latency, duration, and magnitude of vection) every three hours from 9 AM to 9 PM. The results showed that vection was similar at all times measured. Thus, we concluded that vection was unaffected by circadian clock.
Regulation of circadian rhythms
Josef Berger
Journal of Applied Biomedicine , 2004,
Abstract: The human circadian system is evidently regulated by components which can be found in the retina (light input), a suprachiasmatic nucleus in the hypothalamus (clock genes) and the pineal gland (melatonin synthesis). Clock genes are interdependent through two intracellular feedback loops. The pineal gland is not the single important producer of melatonin, as immune cells can also produce this hormone. Immune cells contain active clock genes as SCN cells and we can suggest that the regulation of the circadian system is a component of the neuroimmune regulation of the organism. The endogenous character is dominant in SCN, which is modulated by darkness and which synchronizes organisms to the light/dark regime including immunity. The exogenous character seems to be dominant in the immune system which synchronizes the organism including SCN cells to other environmental stimuli. The mathematical theory of chaos shows that the circadian activity of a cell is derived from ultradian metabolic rhythms; these rhythms support the stability of living systems which can be changed by a limited repertoire of interventions. The complexity of neuroimmune interactions perhaps explains why we are far from knowing the mechanism concerning the regulation of biorhythms despite the vast number of related scientific publications.
Evidence of circadian rhythms in non-photosynthetic bacteria?
María I Soriano, Bego?a Roibás, Ana B García, Manuel Espinosa-Urgel
Journal of Circadian Rhythms , 2010, DOI: 10.1186/1740-3391-8-8
Abstract: Activities and physiological processes taking place with a periodicity of around 24 h have been described in many organisms [1]. Circadian cycles, synchronized and entrained by light and darkness cycles determine in mammals the periods of sleep and vigil, changes in body temperature or hormone production, among other functions. In plants, the release of hormones such as ethylene, certain developmental processes, or the release of seed and root exudates are subject to this periodicity [2]. The absence of circadian cycles is generally assumed for bacteria, except in the case of cyanobacteria, in which photosynthesis and nitrogen fixation are either spatially segregated in heterocyst-forming bacteria, or temporally separated and controlled by circadian periodicity. Both processes would not be possible at the same time in a single cell, because oxygen released during photosynthesis inhibits nitrogenase activity. Circadian rhythms in photosynthetic bacteria are being thoroughly studied, and the molecular mechanisms that allow the functioning and maintenance of the circadian clock are fairly well understood [3]. The clock is composed of three proteins, KaiA, KaiB, and KaiC, which function as a central oscillator through phosphorylation/dephosphorylation cycles. The system is synchronized via a signal input pathway in which sensory proteins are known to transmit light/darkness information to the clock, while a series of clock-controlled regulators transduce the temporal information to downstream processes. Expression of a significant number of genes appears to be modified in response to light/darkness cycles and circadian oscillations, indicating that this type of control is not limited to certain specific features of cyanobacteria. Such broader impact on different physiological processes makes us question the premise of circadian rhythms being circumscribed to this particular group within prokaryotes.The presumed lack of circadian periodicity in the physiology of heterotr
A riot of rhythms: neuronal and glial circadian oscillators in the mediobasal hypothalamus
Clare Guilding, Alun TL Hughes, Timothy M Brown, Sara Namvar, Hugh D Piggins
Molecular Brain , 2009, DOI: 10.1186/1756-6606-2-28
Abstract: Here we demonstrate endogenous circadian rhythms of PER2::LUC expression in discrete subdivisions of the arcuate (Arc) and dorsomedial nuclei (DMH). Rhythms resolved to single cells did not maintain long-term synchrony with one-another, leading to a damping of oscillations at both cell and tissue levels. Complementary electrophysiology recordings revealed rhythms in neuronal activity in the Arc and DMH. Further, PER2::LUC rhythms were detected in the ependymal layer of the third ventricle and in the median eminence/pars tuberalis (ME/PT). A high-fat diet had no effect on the molecular oscillations in the MBH, whereas food deprivation resulted in an altered phase in the ME/PT.Our results provide the first single cell resolution of endogenous circadian rhythms in clock gene expression in any intact tissue outside the SCN, reveal the cellular basis for tissue level damping in extra-SCN oscillators and demonstrate that an oscillator in the ME/PT is responsive to changes in metabolism.The coordinated daily regulation of cycles in rest and activity, food intake and metabolism are crucial for the optimal health of an individual [1-4]. In mammals this daily, or circadian, timekeeping is customarily attributed to the intrinsic activities of autonomous cellular clocks within the suprachiasmatic nuclei (SCN) of the hypothalamus [5,6]. Individual SCN cells sustain robust and synchronized endogenous rhythms in clock gene expression [7]. These enable the SCN to maintain a coherent rhythmic tissue output which underlies its basis as the master clock controlling daily rhythms in physiology and behavior [8-11]. Many peripheral cells and tissues also rhythmically express clock genes, the phases of which are coordinated throughout the organism by the SCN, which is itself entrained by environmental timing cues [12-14].Unlike peripheral circadian pacemakers, there is only limited evidence of overt self-sustained circadian oscillations in the central nervous system, outside of the SCN [1
Ischemic stroke destabilizes circadian rhythms
He Meng, Tiecheng Liu, Jimo Borjigin, Michael M Wang
Journal of Circadian Rhythms , 2008, DOI: 10.1186/1740-3391-6-9
Abstract: Rats were housed in LD 12:12 h conditions and monitored by pineal microdialysis to determine baseline melatonin timing profiles. After demonstration that the circadian expression of melatonin was at steady state, rats were subjected to experimental stroke using two-hour intralumenal filament occlusion of the middle cerebral artery. The animals were returned to their cages, and melatonin monitoring was resumed. The timing of onset, offset, and duration of melatonin secretion were calculated before and after stroke to determine changes in circadian rhythms of melatonin secretion. At the end of the monitoring period, brains were analyzed to determine infarct volume.Rats demonstrated immediate shifts in melatonin timing after stroke. We observed a broad range of perturbations in melatonin timing in subsequent days, with rats exhibiting onset/offset patterns which included: advance/advance, advance/delay, delay/advance, and delay/delay. Melatonin rhythms displayed prolonged instability several days after stroke, with a majority of rats showing a day-to-day alternation between advance and delay in melatonin onset and duration. Duration of melatonin secretion changed in response to stroke, and this change was strongly determined by the shift in melatonin onset time. There was no correlation between infarct size and the direction or amplitude of melatonin phase shifting.This is the first demonstration that stroke induces immediate changes in the timing of pineal melatonin secretion, indicating that cortical and basal ganglia infarction impacts the timing of melatonin rhythms. The heterogeneous direction and amplitude of melatonin shifts suggests that the upstream regulation of hypothalamic timekeeping is likely anatomically diffuse and mechanistically complex. Finally, our study exemplifies the use of pineal microdialysis to evaluate the effect of neurological diseases on circadian function.Stroke is a leading cause of death and disability world-wide. While the immediate co
Circadian rhythms in cognitive performance: implications for neuropsychological assessment
Valdez P,Ramírez C,García A
ChronoPhysiology and Therapy , 2012,
Abstract: Pablo Valdez, Candelaria Ramírez, Aída GarcíaLaboratory of Psychophysiology, School of Psychology, University of Nuevo León, Monterrey, Nuevo León, MéxicoAbstract: Circadian variations have been found in human performance, including the efficiency to execute many tasks, such as sensory, motor, reaction time, time estimation, memory, verbal, arithmetic calculations, and simulated driving tasks. Performance increases during the day and decreases during the night. Circadian rhythms have been found in three basic neuropsychological processes (attention, working memory, and executive functions), which may explain oscillations in the performance of many tasks. The time course of circadian rhythms in cognitive performance may be modified significantly in patients with brain disorders, due to chronotype, age, alterations of the circadian rhythm, sleep deprivation, type of disorder, and medication. This review analyzes the recent results on circadian rhythms in cognitive performance, as well as the implications of these rhythms for the neuropsychological assessment of patients with brain disorders such as traumatic head injury, stroke, dementia, developmental disorders, and psychiatric disorders.Keywords: human circadian rhythms, cognitive performance, neuropsychological assessment, attention, working memory, executive functions
Scheduled Daily Mating Induces Circadian Anticipatory Activity Rhythms in the Male Rat  [PDF]
Glenn J. Landry, Hanna Opiol, Elliott G. Marchant, Ilya Pavlovski, Rhiannon J. Mear, Dwayne K. Hamson, Ralph E. Mistlberger
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040895
Abstract: Daily schedules of limited access to food, palatable high calorie snacks, water and salt can induce circadian rhythms of anticipatory locomotor activity in rats and mice. All of these stimuli are rewarding, but whether anticipation can be induced by neural correlates of reward independent of metabolic perturbations associated with manipulations of food and hydration is unclear. Three experiments were conducted to determine whether mating, a non-ingestive behavior that is potently rewarding, can induce circadian anticipatory activity rhythms in male rats provided scheduled daily access to steroid-primed estrous female rats. In Experiment 1, rats anticipated access to estrous females in the mid-light period, but also exhibited post-coital eating and running. In Experiment 2, post-coital eating and running were prevented and only a minority of rats exhibited anticipation. Rats allowed to see and smell estrous females showed no anticipation. In both experiments, all rats exhibited sustained behavioral arousal and multiple mounts and intromissions during every session, but ejaculated only every 2–3 days. In Experiment 3, the rats were given more time with individual females, late at night for 28 days, and then in the midday for 28 days. Ejaculation rates increased and anticipation was robust to night sessions and significant although weaker to day sessions. The anticipation rhythm persisted during 3 days of constant dark without mating. During anticipation of nocturnal mating, the rats exhibited a significant preference for a tube to the mating cage over a tube to a locked cage with mating cage litter. This apparent place preference was absent during anticipation of midday mating, which may reflect a daily rhythm of sexual reward. The results establish mating as a reward stimulus capable of inducing circadian rhythms of anticipatory behavior in the male rat, and reveal a critical role for ejaculation, a modulatory role for time of day, and a potential confound role for uncontrolled food intake.
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