Circadian Rhythm Of Locomotor Activity Research Articles

Neuron-specific overexpression of core clock genes improves stress-resistance and extends lifespan of Drosophila melanogaster

Gene expression is much altered in aging. We observed age-dependent decline of core clock genes' expression in the whole body of the fruit fly. We hypothesized that inducible overexpression of clock genes (cry, per, tim, cyc and Clk) in the nervous system can improve healthspan of D. melanogaster. We studied the lifespan of transgenic Drosophila and showed life extension for cry, per, cyc and tim genes. It was also the significant positive changes in the stress-resistance of flies overexpressing core clock genes in conditions of hyperthermia, hyperoxia, starvation and persistent lighting. The overexpression of per and cry restore circadian rhythms of locomotor activity. The results presented support the hypotheses that the compensation of circadian oscillator genes expression can improve the healthspan in Drosophila melanogaster.

Influence of Illumination on the Locomotor Activity in Smolts of European River Lamprey Lampetra fluviatilis (L.)

Behavior of smolts of European lamprey and changes in their locomotor activity have been studied at varying illumination regimes. The maximal level of the locomotor activity of the smolts in aquaria and in an Open Field experimental device is recorded at night at the lowest studied illumination (0.9 lx). This maximum coincides in time with the appearance of migrating smolts in the river channel flow. In daytime, at illumination of 900 lx, the locomotor activity of the smolts is lower, which corresponds to the absence of daytime downstream migration. The change in the locomotor activity over 24 h is one of the mechanisms by which the downstream migration of lamprey smolts is achieved. The increase in the locomotor activity starts soon after evening decrease in illumination below 0.1 lx and falls on the first half of night. The period of increased locomotor activity ends before morning twilight. The presence of the circadian rhythms of locomotor activity in smolts of the European river lamprey is suggested.

Spontaneously Diabetic Torii (SDT) Fatty Rat, a Novel Animal Model of Type 2 Diabetes Mellitus, Shows Blunted Circadian Rhythms and Melatonin Secretion

In patients with diabetes mellitus (DM), impairments of circadian rhythms, including the sleep–wake cycle, blood pressure, and plasma melatonin concentrations, are frequently observed. Animal models of DM are also reported to show aberrant circadian rhythms. However, the changes in the circadian rhythms of plasma soluble substances, including melatonin, in diabetic animals are controversial. In the present study, we investigated the circadian rhythms of spontaneous locomotor activity, metabolic parameters (plasma glucose, triglyceride, and total cholesterol), and plasma melatonin concentrations in Spontaneously Diabetic Torii (SDT) fatty rats, a novel animal model of type 2 DM. Although SDT fatty rats exhibited low locomotor activity in the dark phase, no phase shifts were observed. The circadian variations of plasma metabolic parameters were more apparent in the SDT fatty rats compared with control Sprague–Dawley (SD) rats. The circadian rhythms of plasma melatonin concentrations were significantly impaired in SDT fatty rats. To get an insight into the mechanism underlying the impaired melatonin secretion in SDT fatty rats, the expression of arylalkylamine N-acetyltransferase (Aanat) and acetylserotonin O-methyltransferase (Asmt) mRNA, which encode the rate-limiting enzymes for melatonin synthesis, was investigated in the pineal gland. There were no significant differences in Aanat and Asmt expression between the control SD and SDT fatty rats. These results suggest that SDT fatty rats show impaired circadian rhythms and dysregulated melatonin secretion.

Role of the circadian clock in the statistics of locomotor activity in Drosophila.

In many animals the circadian rhythm of locomotor activity is controlled by an endogenous circadian clock. Using custom made housing and video tracking software in order to obtain high spatial and temporal resolution, we studied the statistical properties of the locomotor activity of wild type and two clock mutants of Drosophila melanogaster. We show here that the distributions of activity and quiescence bouts for the clock mutants in light-dark conditions (LD) are very different from the distributions obtained when there are no external cues from the environment (DD). In the wild type these distributions are very similar, showing that the clock controls this aspect of behavior in both regimes (LD and DD). Furthermore, the distributions are very similar to those reported for Wistar rats. For the timing of events we also observe important differences, quantified by how the event rate distributions scale for increasing time windows. We find that for the wild type these distributions can be rescaled by the same function in DD as in LD. Interestingly, the same function has been shown to rescale the rate distributions in Wistar rats. On the other hand, for the clock mutants it is not possible to rescale the rate distributions, which might indicate that the extent of circadian control depends on the statistical properties of activity and quiescence.

Molecular and circuit mechanisms mediating circadian clock output in the Drosophila brain.

A central question in the circadian biology field concerns the mechanisms that translate ~24-hr oscillations of the molecular clock into overt rhythms. Drosophila melanogaster is a powerful system that provided the first understanding of how molecular clocks are generated and is now illuminating the neural basis of circadian behavior. The identity of ~150 clock neurons in the Drosophila brain and their roles in shaping circadian rhythms of locomotor activity have been described before. This review summarizes mechanisms that transmit time-of-day signals from the clock, within the clock network as well as downstream of it. We also discuss the identification of functional multisynaptic circuits between clock neurons and output neurons that regulate locomotor activity.

Interactions between the circadian clock and TGF-β signaling pathway in zebrafish.

BackgroundTGF-β signaling is a cellular pathway that functions in most cells and has been shown to play a role in multiple processes, such as the immune response, cell differentiation and proliferation. Recent evidence suggests a possible interaction between TGF-β signaling and the molecular circadian oscillator. The current study aims to characterize this interaction in the zebrafish at the molecular and behavioral levels, taking advantage of the early development of a functional circadian clock and the availability of light-entrainable clock-containing cell lines.ResultsSmad3a, a TGF-β signaling-related gene, exhibited a circadian expression pattern throughout the brain of zebrafish larvae. Both pharmacological inhibition and indirect activation of TGF-β signaling in zebrafish Pac-2 cells caused a concentration dependent disruption of rhythmic promoter activity of the core clock gene Per1b. Inhibition of TGF-β signaling in intact zebrafish larvae caused a phase delay in the rhythmic expression of Per1b mRNA. TGF-β inhibition also reversibly disrupted, phase delayed and increased the period of circadian rhythms of locomotor activity in zebrafish larvae.ConclusionsThe current research provides evidence for an interaction between the TGF-β signaling pathway and the circadian clock system at the molecular and behavioral levels, and points to the importance of TGF-β signaling for normal circadian clock function. Future examination of this interaction should contribute to a better understanding of its underlying mechanisms and its influence on a variety of cellular processes including the cell cycle, with possible implications for cancer development and progression.

Circadian rhythms of melatonin and behaviour in juvenile sheep in field conditions: Effects of photoperiod, environment and weaning.

Entrainment of circadian rhythms (CR) to the light dark cycle has been well described under controlled, experimental conditions. However, studies in rodents have reported that rhythms in the laboratory are not always reproduced under field conditions. The aim of this study was to characterise the CR of sheep maintained under conditions of standard UK farm animal husbandry and to investigate the effects of environmental challenges presented by season, weaning and changes in housing on CR. Male sheep (n = 9) were kept at pasture, or group housed in barns, under natural photoperiod for one year. CR in locomotor activity were monitored using accelerometry, and 24 h patterns in plasma cortisol and melatonin were measured every 4 h by ELISA. CR was measured before and after weaning, in summer and winter, and at pasture and by barn housing. Cosinor analysis revealed high amplitude, diurnal rhythms in locomotor activity that were disrupted by weaning and by barn housing. Rhythms in winter showed an interrupted night time activity pattern, but only when the sheep were kept at pasture. Cortisol and melatonin secretion followed typical circadian patterns in winter and summer. The CR of the sheep under the field conditions of this study were strikingly robust under basal conditions, but easily disrupted by environmental challenges. Interrupted patterns of activity during the long nights of wintertime, not previously reported for sheep kept in experimental conditions were recorded. Based on these findings, we propose that animals require exposure to more complex environments than the laboratory in order to exhibit their true circadian phenotype.

Reconfiguration of a Multi-oscillator Network by Light in the Drosophila Circadian Clock

The brain clock that drives circadian rhythms of locomotor activity relies on a multi-oscillator neuronal network. In addition to synchronizing the clock with day-night cycles, light also reformats the clock-driven daily activity pattern. How changes in lighting conditions modify the contribution of the different oscillators to remodel the daily activity pattern remains largely unknown. Our data in Drosophila indicate that light readjusts the interactions between oscillators through two different modes. We show that a morning s-LNv > DN1p circuit works in series, whereas two parallel evening circuits are contributed by LNds and other DN1ps. Based on the photic context, the master pacemaker in the s-LNv neurons swaps its enslaved partner-oscillator-LNd in the presence of light or DN1p in the absence of light-to always link up with the most influential phase-determining oscillator. When exposure to light further increases, the light-activated LNd pacemaker becomes independent by decoupling from the s-LNvs. The calibration of coupling by light is layered on a clock-independent network interaction wherein light upregulates the expression of the PDF neuropeptide in the s-LNvs, which inhibits the behavioral output of the DN1p evening oscillator. Thus, light modifies inter-oscillator coupling and clock-independent output-gating to achieve flexibility in the network. It is likely that the light-induced changes in the Drosophila brain circadian network could reveal general principles of adapting to varying environmental cues in any neuronal multi-oscillator system.

High-Amplitude Circadian Rhythms in Drosophila Driven by Calcineurin-Mediated Post-translational Control of sarah.

Post-translational control is a crucial mechanism for circadian timekeeping. Evolutionarily conserved kinases and phosphatases have been implicated in circadian phosphorylation and the degradation of clock-relevant proteins, which sustain high-amplitude rhythms with 24-hr periodicity in animal behaviors and physiology. Here, we report a novel clock function of the heterodimeric Ca2+/calmodulin-dependent phosphatase calcineurin and its regulator sarah (sra) in Drosophila Genomic deletion of the sra locus dampened circadian locomotor activity rhythms in free-running constant dark after entrainment in light-dark cycles. Poor rhythms in sra mutant behaviors were accompanied by lower expression of two oscillating clock proteins, PERIOD (PER) and TIMELESS (TIM), at the post-transcriptional level. RNA interference-mediated sra depletion in circadian pacemaker neurons was sufficient to phenocopy loss-of-function mutation in sra On the other hand, a constitutively active form of the catalytic calcineurin subunit, Pp2B-14DACT, shortened circadian periodicity in locomotor behaviors and phase-advanced PER and TIM rhythms when overexpressed in clock neurons. Heterozygous sra deletion induced behavioral arrhythmicity in Pp2B-14DACT flies, whereas sra overexpression rescued short periods in these animals. Finally, pharmacological inhibition of calcineurin in either wild-type flies or clock-less S2 cells decreased the levels of PER and TIM, likely by facilitating their proteasomal degradation. Taken together, these data suggest that sra negatively regulates calcineurin by cell-autonomously titrating calcineurin-dependent stabilization of PER and TIM proteins, thereby sustaining high-amplitude behavioral rhythms in Drosophila.

β-Adrenergic receptors control brown adipose UCP-1 tone and cold response without affecting its circadian rhythmicity.

Brown adipose tissue (BAT) thermogenic functions are primarily mediated by uncoupling protein (UCP)-1. Ucp1 gene expression is highly induced by cold temperature, via sympathetic nervous system and β-adrenergic receptors (βARs). Ucp1 is also repressed by the clock gene Rev-erbα, contributing to its circadian rhythmicity. In this study, we investigated mice lacking βARs (β-less mice) to test the relationship between βAR signaling and the BAT molecular clock. We found that in addition to controlling the induction of Ucp1 and other key BAT genes at near freezing temperatures, βARs are essential for the basal expression of BAT Ucp1 at room temperature. Remarkably, although basal Ucp1 expression is low throughout day and night in β-less mice, the circadian rhythmicity of Ucp1 and clock genes in BAT is maintained. Thus, the requirement of βAR signaling for BAT activity is independent of the circadian rhythmicity of Ucp1 expression and circadian oscillation of the molecular clock genes. On the other hand, we found that βARs are essential for the normal circadian rhythms of locomotor activity. Our results demonstrate that in addition to controlling the BAT response to extreme cold, βAR signaling is necessary to maintain basal Ucp1 tone and to couple BAT circadian rhythmicity to the central clock.-Razzoli, M., Emmett, M. J., Lazar, M. A., Bartolomucci, A. β-Adrenergic receptors control brown adipose UCP-1 tone and cold response without affecting its circadian rhythmicity.

The Drosophila apterous56f mutation impairs circadian locomotor activity

We investigated effects of apterous mutation ap56f on circadian locomotor activity, eclosion rhythms, and transcript levels of period and timeless in Drosophila. We investigated circadian locomotor activity and eclosion rhythms in ap56f and wild-type flies, their F1 and F2 offspring, and wingless vestigial mutants and show that ap56f disrupts circadian locomotor rhythms in a genetically recessive manner, that is not caused by the absence of wings. The apblt strain also showed impaired circadian activity rhythms, providing independent evidence for a significant role of apterous in circadian locomotor rhythm expression. The ap56f mutation did not disrupt a circadian eclosion rhythm or rhythmic expression of the period and timeless clock genes, indicating that apterous is not essential for circadian clock function, but is necessary for coupling locomotor activity to a circadian clock. Timeless transcription was reduced in ap56f flies in 12:12 LD, suggesting that apterous may modulate core clock gene expression.

A Conserved Circadian Function for the Neurofibromatosis 1 Gene

SUMMARYLoss of the Neurofibromatosis 1 (Nf1) protein, neurofibromin, in Drosophila disrupts circadian rhythms of locomotor activity without impairing central clock function, suggesting effects downstream of the clock. However, the relevant cellular mechanisms are not known. Leveraging the discovery of output circuits for locomotor rhythms, we dissected cellular actions of neurofibromin in recently identified substrates. Herein, we show that neurofibromin affects the levels and cycling of calcium in multiple circadian peptidergic neurons. A prominent site of action is the pars intercerebralis (PI), the fly equivalent of the hypothalamus, with cell-autonomous effects of Nf1 in PI cells that secrete DH44. Nf1 interacts genetically with peptide signaling to affect circadian behavior. We extended these studies to mammals to demonstrate that mouse astrocytes exhibit a 24-hr rhythm of calcium levels, which is also attenuated by lack of neurofibromin. These findings establish a conserved role for neurofibromin in intracellular signaling rhythms within the nervous system.

Regulation of Circadian Behavior by Astroglial MicroRNAs in Drosophila.

We describe a genome-wide microRNA (miRNA)-based screen to identify brain glial cell functions required for circadian behavior. To identify glial miRNAs that regulate circadian rhythmicity, we employed a collection of "miR-sponges" to inhibit miRNA function in a glia-specific manner. Our initial screen identified 20 glial miRNAs that regulate circadian behavior. We studied two miRNAs, miR-263b and miR-274, in detail and found that both function in adult astrocytes to regulate behavior. Astrocyte-specific inhibition of miR-263b or miR-274 in adults acutely impairs circadian locomotor activity rhythms with no effect on glial or clock neuronal cell viability. To identify potential RNA targets of miR-263b and miR-274, we screened 35 predicted miRNA targets, employing RNA interference-based approaches. Glial knockdown of two putative miR-274 targets, CG4328 and MESK2, resulted in significantly decreased rhythmicity. Homology of the miR-274 targets to mammalian counterparts suggests mechanisms that might be relevant for the glial regulation of rhythmicity.

Agomelatine's effect on circadian locomotor rhythm alteration and depressive-like behavior in 6-OHDA lesioned rats

Parkinson's disease (PD) patients often suffer from circadian locomotor rhythms impairment and depression, important non-motor symptoms. It is known that toxin-based animal models of PD can reproduce these features. In a 6-hydroxydopamine (6-OHDA) intranigral model, we first investigated the possible disturbances on circadian rhythms of locomotor activity. The rats were divided into 6-OHDA and Sham groups. After a partial dopaminergic lesion, the 6-OHDA group showed slight alterations in different circadian locomotor rhythms parameters. In a second experiment, we hypothesized agomelatine, an melatoninergic antidepressant with potential to resynchronize disturbed rhythms, could prevent neuronal damage and rhythm alterations in the same 6-OHDA model. The animals were divided into four groups: 6-OHDA+vehicle, 6-OHDA+ago, Sham+vehicle and 6-OHDA+ago. However, the treated animals (agomelatine 50 mg/kg for 22 days) showed an impaired rhythm robustness, and agomelatine did not induce significant changes in the other circadian parameters nor neuroprotection. Finally, in a third experiment, we examined the effects of agomelatine in the 6-OHDA model regarding depressive-like behavior, evaluated by sucrose preference test. The animals were also divided into four groups: 6-OHDA+vehicle, 6-OHDA+ago, Sham+vehicle and 6-OHDA+ago. The toxin infused animals showed a decrease in sucrose preference in comparison with the vehicle infused animals, however, agomelatine did not prevent this decrease. Our findings indicate that agomelatine worsened circadian locomotor rhythm and was not able to reverse the depressive-like behavior of rats in the 6-OHDA PD model.

Treatments with thousands therapeutic doses of meldonium failed to alter the Drosophila’s circadian clocks but negatively affected the germination of Pisum’s seeds

Meldonium is used clinically as an anti-ischaemic drug to treat myocardial infarction and chronic heart failure, and it had become a news making substance after the banning several elite athletes including Maria Sharapova from competitions. Despite this, the majority of possible biological effects of meldonium remained unexplored. We tested two effects, I) on the circadian clocks of fruit fly (Drosophila melanogaster) and II) on the process of pea seed germination (Pisum sativum). I. Comparison of the effects of photoperiod and meldomium on the circadian rhythm of locomotor activity during the 2nd and 3rd days in constant darkness revealed the expected effect of the previous photoperiod whereas meldonium in concentrations ranged from 1 (5 mg/kg) to 10,000 therapeutic doses failed to alter the mechanism of the fly’s circadian clocks. II. A treatment with meldonium in very high concentration (2000 therapeutic doses) negatively affected the process of germination of pea seeds.

Circadian rhythms of body temperature and locomotor activity in the antelope ground squirrel, Ammospermophilus leucurus

We studied circadian rhythms of body temperature and locomotor activity in antelope ground squirrels (Ammospermophilus leucurus) under laboratory conditions of a 12L:12D light-dark cycle and in constant darkness. Antelope ground squirrels are diurnally active and, exceptionally among ground squirrels and other closely related members of the squirrel family in general, they do not hibernate. Daily oscillations in body temperature consisted of a rise in temperature during the daytime activity phase of the circadian cycle and a decrease in temperature during the nighttime rest phase. The body temperature rhythms were robust (71% of maximal strength) with a daily range of oscillation of 4.6°C, a daytime mean of 38.7°C, and a nighttime mean of 34.1°C (24-h overall mean 36.4°C). The body temperature rhythm persisted in continuous darkness with a free-running period of 24.2h. This pattern is similar to that of hibernating species of ground squirrels but with a wave form more similar to that of non-hibernating rodents. Daily oscillations in body temperature were correlated with individual bouts of activity, but daytime temperatures were higher than nighttime temperatures even when comparing short episodes of nocturnal activity that were as intense as diurnal activity. This suggests that although muscular thermogenesis associated with locomotor activity can modify the level of body temperature, the circadian rhythm of body temperature is not simply a consequence of the circadian rhythm of activity.

Pigment-Dispersing Factor-expressing neurons convey circadian information in the honey bee brain.

Pigment-Dispersing Factor (PDF) is an important neuropeptide in the brain circadian network of Drosophila and other insects, but its role in bees in which the circadian clock influences complex behaviour is not well understood. We combined high-resolution neuroanatomical characterizations, quantification of PDF levels over the day and brain injections of synthetic PDF peptide to study the role of PDF in the honey bee Apis mellifera. We show that PDF co-localizes with the clock protein Period (PER) in a cluster of laterally located neurons and that the widespread arborizations of these PER/PDF neurons are in close vicinity to other PER-positive cells (neurons and glia). PDF-immunostaining intensity oscillates in a diurnal and circadian manner with possible influences for age or worker task on synchrony of oscillations in different brain areas. Finally, PDF injection into the area between optic lobes and the central brain at the end of the subjective day produced a consistent trend of phase-delayed circadian rhythms in locomotor activity. Altogether, these results are consistent with the hypothesis that PDF is a neuromodulator that conveys circadian information from pacemaker cells to brain centres involved in diverse functions including locomotion, time memory and sun-compass orientation.

Circadian rhythms of micturition during jet lag.

Micturition behavior follows regular day/night fluctuations, and unwanted increase in micturition could occur during night in jet lag condition. To clarify the effect of jet lag on micturition behavior, we simultaneously detected circadian micturition patterns and locomotor activity rhythms of mice under experimental jet lag conditions, by applying the improved automated Voided Stain on Paper (aVSOP) method. When wild-type (WT) mice were phase-advanced for 8 hours, day-night variation of micturition was disrupted suddenly, and this irregular daily micturition continued until 8 days, although their activity rhythms entrained gradually day by day until 8 days. We also examined how jet lag induced changes of micturition in Per-null mice lacking Per1, Per2 and Per3 genes, whose endogenous clock is completely disrupted. We found both micturition and locomotor activity of Per-null mice promptly entrained to the new LD cycle. These findings suggest that the irregular micturition during jet lag is caused along with the gradual shift of the endogenous clock, and paradoxically, jet lag-associated abnormality was absent when endogenous circadian oscillations were genetically disrupted.

Effects of gender, age, and nutrition on circadian locomotor activity rhythms in the flesh fly Sarcophaga crassipalpis

In many animal species, circadian rhythms of behavior are not constant throughout the lifetime of the individual but rather exhibit at least some degree of plasticity. In the present study, we have examined the potential influences of gender, age, and nutrition (presence or absence of liver) on the expression of circadian locomotor activity rhythms in the flesh fly Sarcophaga crassipalpis. We found no significant differences in endogenous circadian period under constant dark conditions with respect to gender, nutrition, or age for the duration of our experiments. On the other hand, both male and female flesh flies, as expected, were predominantly diurnal under light-dark cycles, but the pattern of entrainment differed between the sexes. Females also displayed higher activity levels than males. Also, in contrast with males, female activity levels increased with age. Moreover, females exhibited an extraordinary, but transient (one to three days), departure from diurnality which we characterize as “extended dark activity” (EDA). This phenomenon appeared as a continuous bout of locomotor activity that extended at least three hours into the early half of the dark phase at levels at least twice the median of the overall locomotor activity for the individual fly. EDA occurred as an age-dependent response to liver consumption, never appearing prior to day 4 post-eclosion but, thereafter, transpiring within one or two days after a 48-h exposure to liver. These results suggest a linkage between physiological events associated with egg provisioning and locomotor activity in the anautogenous flesh fly. Furthermore, our findings identify the existence of multiple influences on the expression of circadian clock-regulated behavior.

Ovariectomy influences the circadian rhythm of locomotor activity and the photic phase shifts in the volcano mouse

Recently, the relationship between the circadian system and female reproduction has been of great interest; ovarian hormones can modify the amount and distribution of daily activity differently in rodent species. The volcano mouse Neotomodon alstoni is a species in which it is possible to study the circadian rhythm of locomotion, and it offers comparative information about the influence of ovaries on the circadian system. In this study, we used infrared crossings to compare free movement in intact and sham-operated or ovariectomized mice. We analyzed behavioral and endocrine changes related to the estrous cycle and locomotor circadian rhythm in free-running mice and photic phase shifting. Evidence shows that intact mice present a scalloped pattern of daily activity during the estrous cycle. In constant darkness, the ovariectomy reduces the total amount of activity, shortens the free-running circadian period of locomotion and increases photic phase shifts during the early subjective night. During entrainment, the ovariectomized mice increased the amplitude of total activity during the scotophase, and delay the time of activity onset. These results suggest that ovarian hormones in N. alstoni modulate the circadian rhythm of locomotor activity in a species-specific manner.