A guideline for analyzing circadian wheel-running behavior in rodents under different lighting conditions (original) (raw)
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Recording and Analysis of Circadian Rhythms in Running-wheel Activity in Rodents
Journal of Visualized Experiments, 2013
When rodents have free access to a running wheel in their home cage, voluntary use of this wheel will depend on the time of day 1-5. Nocturnal rodents, including rats, hamsters, and mice, are active during the night and relatively inactive during the day. Many other behavioral and physiological measures also exhibit daily rhythms, but in rodents, running-wheel activity serves as a particularly reliable and convenient measure of the output of the master circadian clock, the suprachiasmatic nucleus (SCN) of the hypothalamus. In general, through a process called entrainment, the daily pattern of running-wheel activity will naturally align with the environmental light-dark cycle (LD cycle; e.g. 12 hr-light:12 hr-dark). However circadian rhythms are endogenously generated patterns in behavior that exhibit a ~24 hr period, and persist in constant darkness. Thus, in the absence of an LD cycle, the recording and analysis of running-wheel activity can be used to determine the subjective time-of-day. Because these rhythms are directed by the circadian clock the subjective time-of-day is referred to as the circadian time (CT). In contrast, when an LD cycle is present, the time-of-day that is determined by the environmental LD cycle is called the zeitgeber time (ZT). Although circadian rhythms in running-wheel activity are typically linked to the SCN clock 6-8
AJP: Regulatory, Integrative and Comparative Physiology, 2013
Entrainment of circadian behavior rhythms by daily exposure to a running wheel was examined in mice under constant darkness. Spontaneous movement was individually monitored for more than 6 mo by a thermal sensor. After establishment of steady-state free running, mice were placed in a different cage equipped with a running-wheel for 3 h once per day at 6 AM. The daily exchange was continued for 80 days. The number of wheel revolutions during exposure to the running wheel was also measured simultaneously with spontaneous movement. In 13 out of 17 mice, circadian behavior rhythm was entrained by daily wheel exposure, showing a period indistinguishable from 24 h. The entrainment occurred in parallel with an increase in spontaneous movement immediately prior to the daily wheel exposure. A similar preexposure increase was observed in only one of four nonentrained mice. The preexposure increase appeared in 19.5 days on average after the start of daily wheel exposure and persisted for 36 da...
Methods to Record Circadian Rhythm Wheel Running Activity in Mice
Methods in Enzymology, 2005
Forward genetic approaches (phenotype to gene) are powerful methods to identify mouse circadian clock components. The success of these approaches, however, is highly dependent on the quality of the phenotype-specifically, the ability to measure circadian rhythms in individual mice. This article outlines the factors necessary to measure mouse circadian rhythms, including choice of mouse strain, facilities and equipment design and construction, experimental design, high-throughput methods, and finally methods for data analysis. Strain Choice The choice of mouse strain is the most important consideration for any mouse circadian rhythm screen and ultimately dictates the ability to identify mutants. Poor runners or variable wheel running activity will muddle the interpretation of results and increase the number of false-positive mutants. For example, BALB/cJ mice would be a poor choice of strain for a mutant screen. These mice are poor runners and have a highly variable circadian
Biological Rhythm Research, 1997
The sensitivity of the circadian pacemaker of the field mouse Mus booduga to diffuse daylight pulses of 15 min duration and 1000 lux intensity was measured in a series of experiments and a phase response curve (PRC) constructed. The PRC evoked was of type-I with significant quantitative differences compared to the PRCs constructed for other light stimuli (fluorescent and incandescent light sources) of the same intensity and duration. Not only are the advance and delay peaks larger in the daylight PRC, but there is also significant qualitative and quantitative differences in the shape of the PRC. The area under the advance zone of the diffuse daylight PRC (A) was found to be significantly greater than the A of (i) the fluorescent light PRC and of (ii) the incandescent light PRC. The area under the delay zone of the diffuse daylight PRC (D) was also found to be significantly greater compared to D of (i) the fluorescent light PRC and of (ii) the incandescent light PRC. These differences in the shape of the PRCs can only be attributed to the variation in the spectral intensity distribution of the different components in the three light stimuli used since all other factors (e.g. sample size, free-running period, duration and intensity of light pulse etc.) were comparable in the three PRC experiments. We conclude that the circadian photoreceptor(s) of the field mouse M. booduga are sensitive to variations in the spectral composition of light stimuli.
Genes to Cells, 2008
Effects of scheduled exposures to novel environment with a running-wheel were examined on re-entrainment to 8 hour shifted light-dark (LD) cycles of mouse circadian rhythms in locomotor activity and clock gene, Per1, expression in the suprachiasmatic nucleus (SCN) and peripheral tissues. Per1 expression was monitored by a bioluminescence reporter introduced into mice. The animals were exposed to the novel environment for 3 hours from the shifted dark onset for 4 cycles and released into constant darkness. In the phase-advance shift, the circadian rhythm in locomotor activity fully re-entrained in the exposed group, whereas it was in transients in the control. On the other hand, the circadian rhythm of Per1 expression in the SCN almost completely re-entrained in both the control and exposed groups. In the skeletal muscle and lung, the circadian rhythm fully re-entrained in the exposed group, whereas the rhythms in the control did not. In the phase-delay shift, the circadian rhythms in locomotor activity and Per1 expression almost completely re-entrained in both groups. Theses findings indicate that the scheduled exposures to novel environment with a running-wheel differentially accelerate the re-entrainment of the mouse peripheral clocks to 8 hour phase-advanced LD cycles.
Circadian activity rhythms in the spiny mouse, Acomys cahirinus
Physiology & Behavior, 2005
Circadian locomotor rhythms were examined in adult common spiny mice, Acomys cahirinus. Spiny mice demonstrated nocturnal activity, with onset of activity coinciding promptly with onset of darkness. Re-entrainment to 6-h delays of the light-dark cycle was accomplished faster than to 6-h advances. Access to running wheels yielded significant changes in period and duration of daily activity. Novelty-induced wheel running had no effect on phase of activity rhythms. Circadian responses to light at various times of the circadian cycle were temporally similar to those observed in other nocturnal rodent species. No gender differences were observed in any of the parameters measured.
Journal of Comparative Psychology
Environmental conditions, such as the light-dark cycle and temperature, affect the display of circadian rhythmicity and locomotor activity patterns in mammals. Here, we tested the hypothesis that manipulating these environmental conditions would affect wheel-running activity patterns in a diurnal rodent, the Nile grass rat (Arvicanthis niloticus). Whereas grass rats are diurnal in the field, a subset switch from a day-active to a night-active pattern of activity after the introduction of a running wheel. The mechanism of this chronotype switch remains largely unknown. In the present study, grass rats were presented with running wheels in 12:12 light-dark (LD) conditions. First, subjects were exposed to 25 degrees C during the day and 21 degrees C at night, which resulted in 100% of grass rats expressing diurnal behavior. Subjects were then exposed to manipulations of elevated ambient temperature, which resulted in a significant reduction in wheel-running activity. Reducing ambient temperature below 21 degrees C, however, did not disrupt the expression of diurnality or overall activity. Next, lighting intensity was reduced, which resulted in a switch from a diurnal to a nocturnal chronotype in a subset of animals and reduced overall wheel-running activity. Upon return to baseline lighting intensity, patterns of diurnal activity were restored. Altogether, increases in ambient temperature and decreases in lighting intensity significantly reduced overall wheel-running activity. Importantly, dim light resulted in a temporal niche switch in a subset of grass rats, suggesting a critical role for lighting intensity on the expression of wheel-running activity patterns.
Circadian rhythms of locomotor activity in naked mole-rats (Heterocephalus glaber)
Physiology & Behavior, 2000
A wide variety of organisms exhibit various circadian rhythms in their behavior and physiology. Circadian rhythms are regulated by internal clocks that are generally entrained primarily by the environmental light:dark (L:D) cycle. There have been few studies of circadian rhythms in fossorial species that inhabit an environment where day ± night variations are minimal and where exposure to light occurs infrequently. In this study, circadian patterns of wheel-running activity were examined in naked mole-rats (Heterocephalus glaber). Naked mole-rats are fossorial and eusocial, living in colonies of 60 ± 70 animals with only one breeding female. Most individual mole-rats that ran on wheels (65%) exhibited robust circadian rhythms of locomotor activity, entrained to various L:D cycles, and free-ran in constant darkness (DD) with taus averaging 23.5 h. The remainder of the animals either free-ran or were arrhythmic under the various L:D cycles. Mole-rats generally failed to entrain to non-24-h T-cycles with period lengths ranging from T = 23 h to T = 25 h. There was considerable inter-individual variation in the circadian patterns of locomotor activity in naked mole-rats as is observed in other subterranean mammals that have been studied. In contrast to the results obtained when mole-rats were individually housed with access to running wheels, circadian rhythms of general locomotor activity were typically not observed for animals monitored while they were housed in a colony setting. However, clear nocturnal rhythms of general locomotor activity were displayed by four males while residing in their home colonies. Two of these males exhibited the physical appearance of a disperser morph Ð subordinate individuals that are believed to leave their home colonies to achieve reproductive opportunities elsewhere. All four of these males were among the largest males in their respective colonies. These results demonstrate that although naked mole-rats are not frequently exposed to light, the species has retained the capacity to exhibit locomotor patterns of circadian rhythmicity and has the ability to entrain to 24-h L:D cycles. The possible adaptive function of this circadian capacity is discussed.
Circadian rhythms of locomotor activity in Ansell's mole‐rat: are mole‐rat's clocks ticking?
Journal of …, 2008
Circadian rhythms of locomotor activity have been investigated in several African mole-rat species. Even though mole-rats spend most of their lives in underground burrows devoid of light, studies have shown that they do possess circadian rhythms to some extent. We investigated the circadian rhythms of locomotor activity in 11 male Ansell's mole-rats Fukomys anselli from Zambia. In order to determine whether these animals can entrain to light and have endogenous rhythms, they were subjected to different light regimes: first, 12 h light/12 h dark, followed by constant darkness, then returned to 12 h light/12 h dark, which was later inversed to 12 h dark/12 h light. Only two individuals displayed arrhythmic activity patterns whereas the other nine (81.8%) exhibited entrainment of their activity to the light regimes. Locomotory activity of Ansell's mole-rat was predominantly during the dark phase in all light regimes. During constant darkness (DD), only five individuals (45.5%) displayed very weak circadian rhythms that free ran but became more indistinct towards the end of the cycle. Under the second LD light cycle, 90.1% of the animals were active during the night phase of the cycle and when placed under an inverse light cycle, seven individuals still displayed activity predominantly during the dark phase. In conclusion, these results suggest that Ansell's mole-rat does have a weak circadian clock and is able to perceive light and entrain to light cycles.
Running wheel size influences circadian rhythm period and its phase shift in mice
Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 2000
Photoperiod influences the distribution of sleep and waking and electroencephalogram (EEG) power density in the Djungarian hamster. In an experimental procedure combining short photoperiod (SP) and low ambient temperature, the light-dark difference in the amount of sleep was decreased, and the changes in slow-wave activity (SWA) (mean EEG power density between 0.75 and 4.0 Hz) in nonrapid eye movement (NREM) sleep within 24 h were abolished. These findings, obtained in three different groups of animals, suggested that at the lower ambient temperature, the influence of the circadian clock on sleep-wake behavior was diminished. However, it remained unclear whether the changes were due to the photoperiod, ambient temperature, or both. Here, the authors show that EEG and electromyogram recordings in a single group of animals sequentially adapted to a short and long photoperiod (LP) at low ambient temperature (~15°C) confirm that EEG power is reduced in SP. Moreover, the nocturnal sleep-wake behavior and the changes in SWA in NREM sleep over 24 h were restored by returning the animals to LP and retaining ambient temperature at 15°C. Therefore, the effects cannot be attributed to ambient temperature alone but are due to a combined effect of temperature and photoperiod. When the Djungarian hamster adapts to winter conditions, it appears to uncouple sleep regulation from the circadian clock. Figure 4. Time course of EEG power density in nonrapid eye movement sleep in the light (upper two panels) and dark period (lower panels) of the 24-h day recorded in a short and long photoperiod. Curves connect mean values for consecutive 4-h intervals (n = 8).