Pulses of darkness shift the phase of a circadian rhythm in an insectivorous bat

Subbaraj, R.; Chandrashekaran, M. K.

doi:10.1007/bf01350114

Cited by 34 publications

(13 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We hypothesize that this was due to the relationship between the dark pulses, the individual bear's circadian phase, and position on the phase response curve. The general form of the response curves is very similar between nocturnal and diurnal animals (62) and appeared opposite to that of light in our study, supporting similar findings in rodents (4,80). In addition, responses to dark pulses appear to differ between nocturnal and diurnal species with nocturnal species generally being most responsive during the day and diurnal species during the night (7,14,24,30,32,40,45).…”

Section: Discussionsupporting

confidence: 87%

Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment

Ware¹,

Nelson

Robbins

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

September 12, 2012; doi:10.1152/ajpregu.00313.2012.-Seasonal cycles of reproduction, migration, and hibernation are often synchronized to changes in daylength (photoperiod). Ecological and evolutionary pressures have resulted in physiological specializations enabling animals to occupy a particular temporal niche within the diel cycle leading to characteristic activity patterns. In this study, we characterized the annual locomotor activity of captive brown bears (Ursus arctos). Locomotor activity was observed in 18 bears of varying ages and sexes during the active (Mar-Oct) and hibernating (Nov-Feb) seasons. All bears exhibited either crepuscular or diurnal activity patterns. Estimates of activity duration (␣) and synchronization to the daily light:dark cycle (phase angles) indirectly measured photoresponsiveness. ␣ increased as daylength increased but diverged near the autumnal equinox. Phase angles varied widely between active and hibernating seasons and exhibited a clear annual rhythm. To directly test the role of photoperiod, bears were exposed to controlled photoperiod alterations. Bears failed to alter their daily activity patterns (entrain) to experimental photoperiods during the active season. In contrast, photic entrainment was evident during hibernation when the daily photocycle was shifted and when bears were exposed to a skeleton (11:1:11:1) photoperiod. To test whether entrainment to nonphotic cues superseded photic entrainment during the active season, bears were exposed to a reversed feeding regimen (dark-fed) under a natural photocycle. Activity shifted entirely to a nocturnal pattern. Thus daily activity in brown bears is highly modifiable by photoperiod and food availability in a stereotypic seasonal fashion. entrainment; food-entrainable oscillator; hibernation; phase shift; brown bear ACTIVITY PATTERNS are a useful behavioral measure to inform ecological and conservation studies. By examining these patterns, the impact of habitat destruction, food availability, and conspecific interactions can be revealed. Furthermore, a large body of literature has revealed that rather than merely being stimulated or suppressed by light and dark, many activity patterns are generated by a clock-like mechanism (17,60). This biological clock is highly conserved because it enables animals to accurately and reliably perform functions integral to survival due to the predictable nature of the earth's rotation and seasonal changes in daylength (5). The biological clock thus serves as both a timekeeper and calendar.Considerable research has characterized activity patterns of wild brown (Ursus arctos) and black bears (Ursus americanus), although much less is known about the physiological mechanisms that generate them. Both brown and black bears are capable of exhibiting a wide variety of activity patterns depending on season, geographic location, food availability, and human influences, just to name a few (22,27,34,41,49,54,77). Bears exhibit distinct seasonal timing of activities such as reproduction and hyperphagia ...

show abstract

Section: Discussionsupporting

confidence: 87%

Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment

Ware¹,

Nelson

Robbins

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

show abstract

“…For example, exposure of bats, mice, and hamsters kept in constant light (LL) to pulses of darkness for 2-6 h phase-dependently phase resets their behavioral activity rhythms in a characteristic pattern of temporal sensitivity that differs markedly from photic PRCs (4,5,10,16,34). In hamsters, dark pulses evoke phase advances during the middle to late subjective day and phase delays when given at late subjective night and early subjective day (5,16).…”

mentioning

confidence: 99%

“…In hamsters, dark pulses evoke phase advances during the middle to late subjective day and phase delays when given at late subjective night and early subjective day (5,16). Consequently, dark-pulse PRCs were originally hypothesized to be the mirror image of photic PRCs (5,34).…”

mentioning

confidence: 99%

Resetting of the hamster circadian system by dark pulses

Canal

Piggins

2006

American Journal of Physiology-Regulatory, Integrative and Comp

View full text Add to dashboard Cite

-Circadian rhythms of animals are reset by exposure to light as well as dark; however, although the parameters of photic entrainment are well characterized, the phaseshifting actions of dark pulses are poorly understood. Here, we determined the tonic and phasic effects of short (0.25 h), moderate (3 h), and long (6 -9 h) duration dark pulses on the wheel-running rhythms of hamsters in constant light. Moderate-and long-duration dark pulses phase dependently reset behavioral rhythms, and the magnitude of these phase shifts increased as a function of the duration of the dark pulse. In contrast, the 0.25-h dark pulses failed to evoke consistent effects at any circadian phase tested. Interestingly, moderate-and long-dark pulses elevated locomotor activity (wheel-running) on the day of treatment. This induced wheel-running was highly correlated with phase shift magnitude when the pulse was given during the subjective day. This, together with the finding that animals pulsed during the subjective day are behaviorally active throughout the pulse, suggests that both locomotor activity and behavioral activation play an important role in the phase-resetting actions of dark pulses. We also found that the robustness of the wheel-running rhythm was weakened, and the amount of wheel-running decreased on the days after exposure to dark pulses; these effects were dependent on pulse duration. In summary, similarly to light, the resetting actions of dark pulses are dependent on both circadian phase and stimulus duration. However, dark pulses appear more complex stimuli, with both photic and nonphotic resetting properties. phase shift; nonphotic; wheel-running; entrainment ALL LIVING ORGANISMS SHOW temporal organization in their physiology and behavior. Endogenous oscillations with a periodicity of ϳ24 h are called circadian rhythms, and in mammals the main circadian pacemaker or clock is contained in the suprachiasmatic nuclei (SCN) of the hypothalamus (24,25). This SCN clock is synchronized (entrained) by recurring external time cues or zeitgebers. Daily variation in environmental light is a potent zeitgeber, and such photic information is relayed directly to the SCN via the monosynaptic retinohypothalamic tract (14

show abstract

“…The phase response curve (PRC) graphically shows quantitative and qualitative variations of the sensitivity of the SCN to environmental cues like light, dark pulses, behavioral arousal, social entrainment, and pharmacological agents (Subbaraj and Chandrashekaran 1978;Mrosovsky 1988Mrosovsky , 1995Mrosovsky , 1996Barbacka-Surowiak 2000).…”

Section: Introductionmentioning

confidence: 99%

The phase shift of locomotor activity rhythm after application of 8-OH-DPAT under constant light in mice

Bartoszewicz

Barbacka-Surowiak

2010

Biological Rhythm Research

View full text Add to dashboard Cite

The evidence from a variety of studies suggests the involvement of 5-HT in both the response of SCN neurons to light and the phase-resetting properties of nonphotic stimuli. Although it is well known that 8-OH-DPAT serotonin agonist causes a phase shift of the activity rhythm, there are few reports of experiments on the influence of serotonin upon the locomotor activity rhythm of nocturnal rodents kept under constant light (LL) conditions. Here we examine the effect of 8-OH-DPAT (5 mg/kg) on the phase of the locomotor activity rhythm in mice under constant light. The phase response curve (PRC) for 8-OH-DPAT (8-hydroxy-2-[di-n-propyloamino]-tetralin) under LL in mice closely resembled the PRC for dark pulses. PRCs for nonphotic stimuli are characterized by maximal phase advances during mid-subjective day, and generally smaller phase delays during subjective night. Only dark pulses produce phase advances throughout the first half of subjective night. We observed the same effect after administration of 8-OH-DPAT.

show abstract

Pulses of darkness shift the phase of a circadian rhythm in an insectivorous bat

Cited by 34 publications

References 14 publications

Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment

Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment

Resetting of the hamster circadian system by dark pulses

The phase shift of locomotor activity rhythm after application of 8-OH-DPAT under constant light in mice

Contact Info

Product

Resources

About