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Project description:An Amygdalar Local Oscillator Coordinates Cellular and Behavioral Rhythms
| PRJNA1025248 | ENA
Project description:Ultradian (~4 hr) rhythms in locomotor activity that do not depend on the master circadian pacemaker in the suprachiasmatic nucleus have been observed across mammalian species, however, the underlying mechanisms driving these rhythms are unknown. We show that disruption of the dopamine transporter gene lengthens the period of ultradian locomotor rhythms in mice. Period lengthening also results from chemogenetic activation of midbrain dopamine neurons and psychostimulant treatment, while the antipsychotic haloperidol has the opposite effect. We further reveal that striatal dopamine levels fluctuate in synchrony with ultradian activity cycles and that dopaminergic tone strongly predicts ultradian period. Our data indicate that an arousal regulating, dopaminergic ultradian oscillator (DUO) operates in the mammalian brain, which normally cycles in harmony with the circadian clock, but can desynchronize when dopamine tone is elevated, thereby producing aberrant patterns of arousal which are strikingly similar to perturbed sleep-wake cycles comorbid with psychopathology.
| S-EPMC4337656 | biostudies-literature
Project description:The Drosophila circadian oscillator is composed of autoregulatory period/timeless (per/tim) and Clock (Clk) feedback loops that control rhythmic transcription. In the Clk loop, CLOCK-CYCLE heterodimers activate vrille (vri) and PAR domain protein 1epsilon (Pdp1epsilon) transcription, then sequential repression by VRI and activation by PDP1epsilon mediate rhythms in Clk transcription. Because VRI and PDP1epsilon bind the same regulatory element, the VRI/PDP1epsilon ratio is thought to control the level of Clk transcription. Thus, constant high or low PDP1epsilon levels in clock cells should eliminate Clk mRNA cycling and disrupt circadian oscillator function. Here we show that reducing PDP1epsilon levels in clock cells by approximately 70% via RNA interference or increasing PDP1epsilon levels by approximately 10-fold in clock cells does not alter Clk mRNA cycling or circadian oscillator function. However, constant low or high PDP1epsilon levels in clock cells disrupt locomotor activity rhythms despite persistent circadian oscillator function in brain pacemaker neurons that extend morphologically normal projections into the dorsal brain. These results demonstrate that the VRI/PDP1epsilon ratio neither controls Clk mRNA cycling nor circadian oscillator function and argue that PDP1epsilon is not essential for Clk activation. PDP1epsilon is nevertheless required for behavioral rhythmicity, which suggests that it functions to regulate oscillator output.
| S-EPMC1828026 | biostudies-literature
Project description:Sema6D is highly expressed in the amygdala. We used single nucleus RNA sequencing (snRNA-seq) to analyze the roles of Sema6D in the amygdala.
2024-07-12 | GSE216431 | GEO
Project description:For many animal species, knowing when to look for food may be as important as knowing where to look. Rats and other species use a feeding-responsive circadian timing mechanism to anticipate, behaviorally and physiologically, a predictable daily feeding opportunity. How this mechanism for anticipating a daily meal accommodates more than one predictable mealtime is unclear. Rats were trained to press a lever for food, and then limited to one or more daily meals at fixed or systematically varying times of day. The rats were able to anticipate up to 4 of 4 daily meals at fixed times of day and two 'daily' meals recurring at 24 h and 26 h intervals. When deprived of food, in constant dark, lever pressing recurred for multiple cycles at expected mealtimes, consistent with the periodicity of the prior feeding schedule. Anticipation did not require the suprachiasmatic nucleus circadian pacemaker. The anticipation rhythms could be simulated using a Kuramoto model in which clusters of coupled oscillators entrain to specific mealtimes based on initial phase and intrinsic circadian periodicity. A flexibly coupled system of food-entrainable circadian oscillators endows rats with adaptive plasticity in daily programming of foraging activity.
| S-EPMC9166752 | biostudies-literature
Project description:Sleep-wake cycles break down with age, but the causes of this degeneration are not clear. Using a Drosophila model, we addressed the contribution of circadian mechanisms to this age-induced deterioration. We found that in old flies, free-running circadian rhythms (behavioral rhythms assayed in constant darkness) have a longer period and an unstable phase before they eventually degenerate. Surprisingly, rhythms are weaker in light-dark cycles and the circadian-regulated morning peak of activity is diminished under these conditions. On a molecular level, aging results in reduced amplitude of circadian clock gene expression in peripheral tissues. However, oscillations of the clock protein PERIOD (PER) are robust and synchronized among different clock neurons, even in very old, arrhythmic flies. To improve rhythms in old flies, we manipulated environmental conditions, which can have direct effects on behavior, and also tested a role for molecules that act downstream of the clock. Coupling temperature cycles with a light-dark schedule or reducing expression of protein kinase A (PKA) improved behavioral rhythms and consolidated sleep. Our data demonstrate that a robust molecular timekeeping mechanism persists in the central pacemaker of aged flies, and reducing PKA can strengthen behavioral rhythms.
| S-EPMC3353743 | biostudies-literature
Project description:Oscillators coupled in a network can synchronize with each other to yield a coherent population rhythm. How do multiple such rhythms interact with each other? Do these collective oscillations synchronize like individual oscillators? We show that this is not the case: for strong, inhibitory coupling rhythms can become synchronized by noise. In contrast to stochastic synchronization, this new mechanism synchronizes the rhythms even if the noisy inputs to different oscillators are completely uncorrelated. Key for the synchrony across networks is the reduced synchrony within the networks: it substantially increases the frequency range across which the networks can be entrained by other networks or by periodic pacemaker-like inputs. We demonstrate this type of robust synchronization for different classes of oscillators and network connectivities. The synchronization of different population rhythms is expected to be relevant for brain rhythms.
| S-EPMC5934367 | biostudies-literature
Project description:Molecular mechanisms responsible for 24 h circadian oscillations, entrainment to external cues, encoding of day length and the time-of-day effects have been well studied experimentally. However, it is still debated from the molecular network point of view whether each cell in suprachiasmatic nuclei harbors two molecular oscillators, where one tracks dawn and the other tracks dusk activities. A single cell dual morning and evening oscillator was proposed by Daan et al., based on the molecular network that has two sets of similar non-redundant per1/cry1 and per2/cry2 circadian genes and each can independently maintain their endogenous oscillations. Understanding of dual oscillator dynamics in a single cell at molecular level may provide insight about the circadian mechanisms that encodes day length variations and its response to external zeitgebers. We present here a realistic dual oscillator model of circadian rhythms based on the series of hypotheses proposed by Daan et al., in which they conjectured that the circadian genes per1/cry1 track dawn while per2/cry2 tracks dusk and they together constitute the morning and evening oscillators (dual oscillator). Their hypothesis also provides explanations about the encoding of day length in terms of molecular mechanisms of per/cry expression. We frame a minimal mathematical model with the assumption that per1 acts a morning oscillator and per2 acts as an evening oscillator and to support and interpret this assumption we fit the model to the experimental data of per1/per2 circadian temporal dynamics, phase response curves (PRC's), and entrainment phenomena under various light-dark conditions. We also capture different patterns of splitting phenomena by coupling two single cell dual oscillators with neuropeptides vasoactive intestinal polypeptide (VIP) and arginine vasopressin (AVP) as the coupling agents and provide interpretation for the occurrence of splitting in terms of ME oscillators, though they are not required to explain the morning and evening oscillators. The proposed dual oscillator model based on Daan's hypothesis supports per1 and per2 playing the role of morning and evening oscillators respectively and this may be the first step towards the understanding of the core molecular mechanism responsible for encoding the day length.
| S-EPMC5423656 | biostudies-literature
Project description:A group of postnatal neurodevelopmental disorders collectively referred to as MeCP2 disorders are caused by aberrations in the gene encoding methyl-CpG-binding protein 2 (MECP2). Loss of MeCP2 function causes Rett syndrome (RTT), whereas increased MeCP2 dosage causes MECP2 duplication or triplication syndromes. MeCP2 acts as a transcriptional repressor, however, the gene expression changes observed in the hypothalamus and cerebellum of MeCP2 disorder mouse models suggest that MeCP2 can also upregulate gene expression. In this study, we compared gene expression changes in the amygdalae of mice lacking MeCP2 (Mecp2-null) and mice overexpressing MeCP2 (MECP2-TG). We chose the amygdala because it is a neuroanatomical region implicated in the control of anxiety and social behavior, two prominent phenotypes in MECP2-TG mice, and hypothesized that transcriptional profiling of this particular brain region may reveal expression changes relevant to heightened anxiety-like behavior and abnormal social behavior. A total of 1,060 genes were altered in opposite directions in both MeCP2 mouse models compared with wild-type littermates, with ~60% up-regulated and ~40% down-regulated. Interestingly, we found a significant enrichment of anxiety- and/or social behavior-related genes among the differentially expressed genes. To determine whether these genes contribute to the anxiety and social behavior phenotypes in MECP2-TG mice, we performed genetic and pharmacologic studies and found that a reduction in Crh suppresses anxiety-like behavior, and a reduction in Oprm1 improves social approach behavior. These studies suggest that MeCP2 impacts molecular pathways involved in anxiety and social behavior, and provide insight into potential therapies for MeCP2 disorders. This study is published in Nature Genetics http://dx.doi.org/10.1038/ng.1066. Total amygdala RNA samples were collected from Mecp2-null male mice (n=4), MECP2-transgenic male mice (n=5), and their wild type male littermates at 6 weeks of age (n=4, n=5 for each group respectively).
2012-01-08 | E-GEOD-33457 | biostudies-arrayexpress
Project description:A system of coupled oscillators can exhibit a rich variety of dynamical behaviors. When we investigate the dynamical properties of the system, we first analyze individual oscillators and the microscopic interactions between them. However, the structure of a coupled oscillator system is often hierarchical, so that the collective behaviors of the system cannot be fully clarified by simply analyzing each element of the system. For example, we found that two weakly interacting groups of coupled oscillators can exhibit anti-phase collective synchronization between the groups even though all microscopic interactions are in-phase coupling. This counter-intuitive phenomenon can occur even when the number of oscillators belonging to each group is only two, that is, when the total number of oscillators is only four. In this paper, we clarify the mechanism underlying this counter-intuitive phenomenon for two weakly interacting groups of two oscillators with global sinusoidal coupling.
| S-EPMC4003481 | biostudies-other