Photoperiod differentially modulates photic and nonphotic phase response curves of hamsters

Evans, Jennifer; Elliott, Jeffrey A.; Gorman, Michael R.

doi:10.1152/ajpregu.00456.2003

Cited by 43 publications

(44 citation statements)

References 43 publications

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“…However, photic and nonphotic effects on the clock can be dissociated. As discussed earlier, the magnitude of phase shifts to light is affected by prior photoperiod (shifts are smaller following exposure to long vs. short days), but the magnitude of activity-induced shifts has recently been shown to be unrelated to photoperiod (Evans et a/., 2004). The results of the present study now demonstrate the converse; a manipulation that can strongly potentiate nonphotic shifts does not affect a light input pathway to the clock.…”

Section: Discussionsupporting

confidence: 73%

“…It is conceivable, for example, that the phase resetting effect of NMDA was in some way down-regulated as a result of exposure to LL so as to precisely offset the functional consequences of decreased amplitude. In fact, increased photoperiod has been shown to attenuate photic resetting in nocturnals (Evans, et al, 2004). Their results showed that light-induced phase shifts are larger in hamsters housed in LD 10:14 vs. 14:lO.…”

Section: Discussionmentioning

confidence: 96%

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Differential effects of constant light on circadian clock resetting by photic and nonphotic stimuli in Syrian hamsters

Landry

Mistlberger

2005

Brain Research

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Section: Discussionsupporting

confidence: 73%

Section: Discussionmentioning

confidence: 96%

Differential effects of constant light on circadian clock resetting by photic and nonphotic stimuli in Syrian hamsters

Landry

Mistlberger

2005

Brain Research

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“…After approximately 1 mo in a short photoperiod, nocturnal rodents shift more in response to a light pulse during the early night than rodents exposed to long days (51,53). The isolated SCN of animals exposed to short days show a narrower peak of daily multiunit activity and, like the behavior, a larger phase shift following stimulation (54).…”

Section: Discussionmentioning

confidence: 96%

“…For example, diurnal sparrows exposed to 36 or 48 h of light before an 8-h advance or delay in their light cycle entrained more rapidly than birds subjected to darkness during the same interval (46). A number of agents including triazolam, Sildenafil, adrenalectomy, scheduled activity during usual rest, and dim light at night have been indicated to accelerate entrainment (47)(48)(49)(50)(51)(52). We propose that paradigms such as these may transiently reduce synchrony among SCN neurons or perhaps other circadian oscillators and, thus, speed entrainment.…”

Section: Discussionmentioning

confidence: 99%

A neuropeptide speeds circadian entrainment by reducing intercellular synchrony

Harang

Meeker

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

115

117

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Shift work or transmeridian travel can desynchronize the body's circadian rhythms from local light-dark cycles. The mammalian suprachiasmatic nucleus (SCN) generates and entrains daily rhythms in physiology and behavior. Paradoxically, we found that vasoactive intestinal polypeptide (VIP), a neuropeptide implicated in synchrony among SCN cells, can also desynchronize them. The degree and duration of desynchronization among SCN neurons depended on both the phase and the dose of VIP. A model of the SCN consisting of coupled stochastic cells predicted both the phase-and the dosedependent response to VIP and that the transient phase desynchronization, or "phase tumbling", could arise from intrinsic, stochastic noise in small populations of key molecules (notably, Period mRNA near its daily minimum). The model also predicted that phase tumbling following brief VIP treatment would accelerate entrainment to shifted environmental cycles. We tested this using a prepulse of VIP during the day before a shift in either a light cycle in vivo or a temperature cycle in vitro. Although VIP during the day does not shift circadian rhythms, the VIP pretreatment approximately halved the time required for mice to reentrain to an 8-h shifted light schedule and for SCN cultures to reentrain to a 10-h shifted temperature cycle. We conclude that VIP below 100 nM synchronizes SCN cells and above 100 nM reduces synchrony in the SCN. We show that exploiting these mechanisms that transiently reduce cellular synchrony before a large shift in the schedule of daily environmental cues has the potential to reduce jet lag.circadian oscillator | biological clock | vasopressin | vasoactive intestinal peptide | period gene C ircadian rhythms of living organisms entrain (synchronize) to daily environmental cues such as light and dark. Living organisms have not evolved to make large daily adjustments in their circadian timing, so it is a challenge for them to respond to changes such as those that humans are subjected to during shift work and travel across time zones. Long-term misalignment between internal circadian rhythms in mammals and environmental cycles can induce physiological and psychological abnormalities, including depression, cancer, heart problems, obesity, and increased mortality (1, 2).The master circadian pacemaker in mammals, the bilateral suprachiasmatic nucleus (SCN), is composed of ∼20,000 neurons that synchronize their daily rhythms to each other and entrain to ambient light cycles (3, 4). Vasoactive intestinal polypeptide (VIP), released in the SCN as a function of circadian time and light intensity (5-7), plays a critical role in this circadian synchronization. In the absence of VIP or its receptor, VPAC2R, SCN neurons fail to synchronize to each other and consequently many daily rhythms of the organism are lost (8-12). The addition of VIP to SCN cultures induces the production of Period (Per) 1 and 2 (13), two genes implicated in light-induced resetting (14-16), and shifts rhythms in behavior and SCN physiology (17-21). Notably...

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“…In contrast, activity-induced phase shifts associated with novel running wheels are caused by suppression of Period gene expression in the SCN of wild-type (WT) hamsters during subjective day (Maywood et al, 1999). Furthermore, the magnitude of phase shifts in response to photic stimuli is dependent on photoperiod, whereas that of nonphotic phase shifts is not (Evans et al, 2004). The tau mutation has been reported to increase the amplitude of nonphotic responses (Mrosovsky, et al, 1992; Biello and Mrosovsky, 1996).…”

mentioning

confidence: 99%

Phase Resetting in Duper Hamsters

2015

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The duper mutation in Syrian hamsters shortens the free-running period of locomotor activity (τDD) to about 23 h and results in a type 0 phase-response curve (PRC) to 15-min light pulses. To determine whether exaggerated phase shifts are specific to photic cues and/or restricted to subjective night, we subjected hamsters to novel wheel confinements and dark pulses during subjective day. Small phase shifts elicited by the nonphotic cue were comparable in mutant and wild-type (WT) hamsters, but dark pulses triggered larger shifts in dupers. To assess further the effects of the duper mutation on light-dark transitions, we transferred hamsters between constant light (LL) and constant dark (DD) or between DD and LL at various circadian phases. Duper hamsters displayed significantly larger phase shifts than WT hamsters when transferred from LL to DD during subjective day and from DD to LL during subjective night. The variability of phase shifts in response to all light/dark transitions was significantly greater in duper hamsters at all time points. In addition, most duper hamsters, but none of the WTs, displayed transient ultradian wheel-running patterns for 5 to 12 days when transferred from light to dark at CT 18. The χ2 periodogram and autocorrelation analyses indicate that these ultradian patterns differ from the disruption of rhythmicity by SCN lesions or exposure to constant bright light. We conclude that the duper mutation specifically amplifies phase shifts to photic cues and may destabilize coupling of circadian organization upon photic challenge due to weakened coupling among components of the circadian pacemaker. Mathematical modeling of the circadian pacemaker supports this hypothesis.

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Photoperiod differentially modulates photic and nonphotic phase response curves of hamsters

Cited by 43 publications

References 43 publications

Differential effects of constant light on circadian clock resetting by photic and nonphotic stimuli in Syrian hamsters

Differential effects of constant light on circadian clock resetting by photic and nonphotic stimuli in Syrian hamsters

A neuropeptide speeds circadian entrainment by reducing intercellular synchrony

Phase Resetting in Duper Hamsters

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