Individual variation in reentrainment after phase shifts of light-dark cycle in a diurnal rodent Octodon degus

1997 ◽  
Vol 273 (2) ◽  
pp. R739-R746 ◽  
Author(s):  
S. E. Labyak ◽  
T. M. Lee
Keyword(s):  
Light Pulse ◽  
Phase Delay ◽  
Interindividual Variation ◽  
Constant Darkness ◽  
Response Curves ◽  
Octodon Degus ◽  
Light Pulses ◽  
Significant Phase ◽  
Free Running ◽  
Phase Relationships

The rate and pattern of activity and temperature reentrainment was determined after 3-, 6-, and 9-h phase advances and phase delays in two groups of Octodon degus for whom phase response curves (PRCs) to light and dark pulses and free-running periods (tau) in constant darkness and constant light had previously been determined [T.M. Lee and S. E. Labyak. Am. J. Physiol. 273 (Regulatory Integrative Comp. Physiol. 42): R278-R286, 1997.]. We predicted that individuals with light-pulse PRCs containing both significant phase delay and phase advance regions would phase delay more rapidly than individuals lacking significant phase delays after light pulses. We also expected that animals without a phase delay region in the light-pulse PRC would demonstrate more temporary circadian abnormalities during the period of reentrainment (periods of masking, bimodal patterns of activity, and abnormal phase relationships between activity and temperature). Degus with light-pulse PRCs containing both a significant phase-delay and -advance region reentrained significantly faster and with fewer disrupted patterns of entrainment after 6- and 9-h phase delays than degus without phase-delay regions in the PRC. The rate of reentrainment after phase advances did not differ between animals with the two types of PRC except for temperature after a 6-h phase shift. Because animals with and without phase-delay regions in the light-pulse PRC had equivalent tau s, the interindividual variation in reentrainment is best explained by the fundamental differences in the light-pulse PRCs. The variation of rate and pattern of reentrainment for both groups of animals were reasonably predicted or explained by knowledge of the light-pulse and dark-pulse PRCs.

Free-running rhythms and light- and dark-pulse phase response curves for diurnal Octodon degus (Rodentia)

1997 ◽  
Vol 273 (1) ◽  
pp. R278-R286 ◽  
Author(s):  
T. M. Lee ◽  
S. E. Labyak
Keyword(s):  
Light Intensity ◽  
Phase Response ◽  
Response Curves ◽  
Phase Response Curves ◽  
Octodon Degus ◽  
Light Pulses ◽  
Significant Phase ◽  
Free Running ◽  
Dark Pulse ◽  
Diurnal Mammal

Only rarely have precise, short-duration light pulses been used to generate phase response curves (PRCs) in diurnal mammals as done for nocturnal mammals, and a dark-pulse PRC has never been generated for a diurnal mammal. In addition, the relationship between free-running rhythms in different light intensities and PRCs has not been explored in diurnal mammals. We examined these relationships in Octodon degus, a diurnal hystricomorph rodent. Male degus lengthened the circadian period (tau) and duration of daily activity (alpha) after an increase in light intensity from 0 (DD) to 250 lx, and tau was furthered lengthened when light intensity increased from 580 to 5,800 lx. To generate a light-pulse PRC, degus were housed in DD and exposed to 20-min light pulses (250 lx) and phase shifts recorded across the circadian day. Two different PRCs were generated in response to 20-min light pulses. The majority of animals produced significant phase delays between circadian time (CT) 0 and CT 6, phase advances between CT 13 and CT 22, and a nonsignificant response period between CT 8 and CT 13. Two animals produced a PRC devoid of significant phase delays, producing only significant phase advances between CT 17 and CT 24. To generate a dark-pulse PRC, animals were moved to LL (580 lx) and exposed to 1-h dark pulses. After dark pulses degus produced significant phase delays between CT 20 and CT 8, advances from CT 10 to CT 17, and nonsignificant responses between CT 18 and CT 20. This is the first report of a PRC to dark-pulse stimuli for a diurnal mammal. Thus light- and dark-pulse PRCs can be generated in a comparable way to those of nocturnal rodents, and we conclude that nocturnal and diurnal rodents use similar photic signals to produce somewhat different PRCs.

Light induces c-fos and per1 expression in the suprachiasmatic nucleus of arrhythmic hamsters

2005 ◽  
Vol 289 (5) ◽  
pp. R1381-R1386 ◽  
Author(s):  
Monique T. Barakat ◽  
Bruce F. O’Hara ◽  
Vinh H. Cao ◽  
H. Craig Heller ◽  
Norman F. Ruby
Keyword(s):  
Suprachiasmatic Nucleus ◽  
Light Pulse ◽  
Significant Proportion ◽  
Phase Delay ◽  
Phodopus Sungorus ◽  
Constant Darkness ◽  
Tissue Sections ◽  
Light Pulses ◽  
Siberian Hamsters

Locomotor activity rhythms in a significant proportion of Siberian hamsters ( Phodopus sungorus sungorus) become arrhythmic after the light-dark (LD) cycle is phase-delayed by 5 h. Arrhythmia is apparent within a few days and persists indefinitely despite the presence of the photocycle. The failure of arrhythmic hamsters to regain rhythms while housed in the LD cycle, as well as the lack of any masking of activity, suggested that the circadian system of these animals had become insensitive to light. We tested this hypothesis by examining light-induced gene expression in the suprachiasmatic nucleus (SCN). Several weeks after the phase delay, arrhythmic and reentrained hamsters were housed in constant darkness (DD) for 24 h and administered a 30-min light pulse 2 h after predicted dark onset because light induces c- fos and per1 genes at this time in entrained animals. Brains were then removed, and tissue sections containing the SCN were processed for in situ hybridization and probed with c- fos and per1 mRNA probes made from Siberian hamster cDNA. Contrary to our prediction, light pulses induced robust expression of both c- fos and per1 in all reentrained and arrhythmic hamsters. A separate group of animals held in DD for 10 days after the light pulse remained arrhythmic. Thus, even though the SCN of these animals responded to light, neither the LD cycle nor DD restored rhythms, as it does in other species made arrhythmic by constant light (LL). These results suggest that different mechanisms underlie arrhythmicity induced by LL or by a phase delay of the LD cycle. Whereas LL induces arrhythmicity by desynchronizing SCN neurons, phase delay-induced arrhythmicity may be due to a loss of circadian rhythms at the level of individual SCN neurons.

Extraretinal photoreception in the lizard Sceloporus occidentalis: phase response curve

1985 ◽  
Vol 248 (4) ◽  
pp. R407-R414
Author(s):  
H. Underwood
Keyword(s):  
Phase Response Curve ◽  
Circadian System ◽  
Phase Response ◽  
Fluorescent Light ◽  
Response Curves ◽  
Sceloporus Occidentalis ◽  
Light Pulses ◽  
Threefold Increase ◽  
Free Running ◽  
Free Running Period

All submammalian vertebrates have extraretinal photoreceptors (ERR) that can mediate entrainment of circadian rhythms to 24-h light-dark (LD) cycles. Phase response curves (PRC) for 6-h fluorescent light pulses were generated for lizards (Sceloporus occidentalis) previously subjected to sectioning of both optic nerves (ONX). The PRC for ONX lizards (only ERRs present) shows a threefold increase in the amplitude of both the advance and delay portions of the PRC compared with a PRC previously generated for sighted S. occidentalis. Also, in contrast to sighted lizards the area of the advance part of the PRC of ONX lizards is greater than the delay portion. Consistent with the shape of the respective PRCs in ONX vs. sighted lizards are the following facts. 1) The range of entrainment to LD cycles is greater in ONX lizards; some sighted lizards free-ran when exposed to LD 6:21.5 or LD 6:23.5 but entrained after ONX lizards reentrained to an 8-h shift in the phase of a LD 6:18 cycle significantly faster than sighted lizards. 3) Forty-two percent of ONX lizards showed a shorter free-running period (tau) in LL than DD, whereas 90% of sighted lizards showed a longer free-running period in LL than in DD. In those lizards in which tau LL greater than tau DD, the the average tau change in ONX lizards in was significantly less than that observed in sighted lizards. These results are consistent with the hypothesis that the eyes have an "inhibitory" role in the circadian system of S. occidentalis.

Social cues modulate free-running circadian activity rhythms in the diurnal rodent, Octodon degus

1997 ◽  
Vol 273 (2) ◽  
pp. R797-R804 ◽  
Author(s):  
N. Goel ◽  
T. M. Lee
Keyword(s):  
Active Phase ◽  
Social Cues ◽  
Constant Darkness ◽  
Circadian Activity ◽  
Mutual Synchronization ◽  
Octodon Degus ◽  
Activity Rhythms ◽  
Female Partners ◽  
Free Running ◽  
Activity Onset

Two experiments assessed the effects of social cues and daily disturbance on the circadian locomotor activity rhythms of Octodon degus housed in constant darkness. In experiment 1, females in free-running conditions were housed alone or with entrained female partners ("donors") in cages on either side of a mesh barrier. Donors were removed daily and entrained to 1 h of light, and as a control, the cages of singly housed animals were rustled daily coincident with donor removal and replacement. None of the animals housed alone entrained to daily disturbances presented during the active phase, and seven of eight degus failed to show changes in the circadian period (tau) or phase of their rhythms. In contrast, although the presence of entrained donors did not elicit full entrainment of free-running rhythms, five of six animals demonstrated partial entrainment for 5-12 days (of 30 days), four of six altered phase of activity onset, and six of six lengthened tau of circadian rhythms. In experiment 2, females whose free-running circadian activity rhythms were at least 10 h out of phase were housed together in pairs. None of the pairs demonstrated mutual synchronization of their activity rhythms, although 8 of 12 degus modified phase of activity onset and 9 of 12 animals altered tau. We conclude social information in the absence of light, is sufficient for partial entrainment and for changes in tau and phase of free-running rhythms in this diurnal rodent.

Circadian control of oviposition activity in Ostrinia nubilalis

1980 ◽  
Vol 239 (3) ◽  
pp. R259-R264 ◽  
Author(s):  
S. D. Skopik ◽  
M. Takeda
Keyword(s):  
Ostrinia Nubilalis ◽  
European Corn Borer ◽  
Phase Response Curve ◽  
Constant Darkness ◽  
Corn Borer ◽  
Light Pulses ◽  
Circadian Control ◽  
Control Light ◽  
Phase Relationships

Oviposition activity in the European corn borer, Ostrinia nubilalis, is under circadian control. Light cycles entrain the rhythm, and the system free-runs in constant darkness (DD) with a circadian period (tau). The lability of tau is evident in the DD free runs following entrainment to various light cycles. Oviposition activity is strongly suppressed in constant light but a circadian rhythm is initiated upon transfer to DD. The phase-response curve (PRC) for 1-h light pulses is type 1, not type 0 as predicted by Beck's dual system theory. The PRC can be used to predict entrained steady states in non-24-h light cycles (T's). Predicted phase relationships between the light component of the cycle and the rhythm in T19 and T26 are in close agreement with the observed peaks of oviposition. Symmetric skeleton photoperiods (two 1-h light pulses per cycle) also entrain the rhythm to the shorter of the two alternatives that are possible in these regimes.

Dark pulses affect the circadian rhythm of activity in hamsters kept in constant light

1982 ◽  
Vol 242 (1) ◽  
pp. R44-R50 ◽  
Author(s):  
G. B. Ellis ◽  
R. E. McKlveen ◽  
F. W. Turek
Keyword(s):  
Response Curve ◽  
Phase Response Curve ◽  
Circadian System ◽  
Constant Light ◽  
Constant Darkness ◽  
Light Pulses ◽  
Subjective Night ◽  
Free Running ◽  
Male Golden Hamsters ◽  
Formal Properties

We compared the effects of light pulses in constant darkness (DD) and dark pulses in constant light (LL) on the free-running rhythm of locomotor activity in male golden hamsters. Light pulses yielded advances, delays, or no change in the rhythm of activity. These data conform to a typical phase-response curve; this curve was unaffected by pinealectomy. Dark pulses occurring either late in the subjective night or early in the subjective day had little effect. In contrast, dark pulses occurring either late in the subjective day or early in the subjective night altered the rhythm in one of three ways: advance of the rhythm; splitting into two components; or induction of a new component, in phase with the pulse. Because dark pulses in LL perturb the circadian system in a different manner than do light pulses in DD, they may have value in identifying heretofore unknown aspects of circadian systems. As such, the use of dark pulses to perturb circadian rhythmicity will be a useful tool in examining the formal properties of circadian systems.

Effects of daily melatonin injections on activity rhythms of rats in constant light

1987 ◽  
Vol 253 (1) ◽  
pp. R101-R107 ◽  
Author(s):  
M. J. Chesworth ◽  
V. M. Cassone ◽  
S. M. Armstrong
Keyword(s):  
Locomotor Activity ◽  
Saline Solution ◽  
Constant Light ◽  
Constant Darkness ◽  
Circadian Activity ◽  
Activity Rhythms ◽  
Melatonin Administration ◽  
Free Running ◽  
Circadian Patterns ◽  
Phase Relationships

Although from pinealectomy studies the pineal body does not appear to participate in the generation of circadian rhythms of mammals, daily injections of the pineal hormone melatonin entrain free-running locomotor activity rhythms of rats in constant darkness. The aim of the present study was to determine whether rats whose circadian activity and drinking rhythms were disrupted in constant light (LL) could be synchronized by daily melatonin administration. Rats were subjected to a regime of gradually increasing photoperiod until they were maintained in LL. Rats whose rhythms became disrupted or showed intact free-running rhythms were injected daily with either melatonin (1 mg/kg) or vehicle (ethanol-saline) solution. Daily melatonin injections either synchronized or partly synchronized disrupted circadian patterns of activity. In contrast to previous findings from experiments conducted in constant darkness, melatonin did not entrain but only partly synchronized intact free-running rhythms. Results are interpreted in terms of melatonin acting on the coupling or phase relationships between oscillators generating circadian locomotor activity rhythms.

Circadian pacemakers in lizards: phase-response curves and effects of pinealectomy

1983 ◽  
Vol 244 (6) ◽  
pp. R857-R864 ◽  
Author(s):  
H. Underwood
Keyword(s):  
Continuous Light ◽  
Phase Response ◽  
Fluorescent Light ◽  
Response Curves ◽  
Continuous Darkness ◽  
Phase Response Curves ◽  
Light Pulses ◽  
Running Activity ◽  
Free Running ◽  
Free Running Period

Phase-response curves (PRCs) for 6-h fluorescent light pulses are described for both intact (sham-pinealectomized) and pinealectomized iguanid lizards (Sceloporus occidentalis). Although strongly diurnal in habit the PRC for intact lizards is more typical of those seen in nocturnal rodents. Other "nocturnal" characteristics of this lizard include the fact that the average free-running period (tau) is less than 24 h and the average tau in continuous light is longer than that observed in continuous darkness. The PRC for pinealectomized lizards is greatly distorted relative to that obtained from intact lizards. This "distortion" is discussed in terms of the role of the pineal as a coupling device or as a pacemaker within a multioscillator circadian system. In some individuals pinealectomy was also associated with 1) increased instability in free-running activity rhythms or arrhythmicity and 2) nocturnal entrainment to LD 12:12.

Are membrane properties essential for the circadian rhythm of Gonyaulax?

1984 ◽  
Vol 247 (2) ◽  
pp. R250-R256
Author(s):  
H. G. Scholubbers ◽  
W. Taylor ◽  
L. Rensing
Keyword(s):  
Circadian Rhythm ◽  
Phase Shift ◽  
Fluorescence Polarization ◽  
The Other ◽  
Membrane Properties ◽  
Response Curves ◽  
Whole Cells ◽  
Different Temperatures ◽  
Free Running ◽  
Free Running Period

Membrane properties of whole cells of Gonyaulax polyedra were measured by fluorescence polarization. Circadian changes of fluorescence polarization exist in exponentially growing cultures. They show an amplitude larger than that of stationary cultures, indicating that a part of the change is due to or amplified by an ongoing cell cycle. Measurements of parameters of the circadian glow rhythm were analyzed for possible correlation with the membrane data. Considerable differences (Q10 = 2.5-3.0) in fluorescence polarization were found in cultures kept at different temperatures ranging from 15 to 27.5 degrees C. The free-running period length at different temperatures, on the other hand, differed only slightly (Q10 = 0.9-1.1). Stationary cultures showed higher fluorescence polarization compared with growing cultures, whereas the free-running period lengths did not differ in cultures of various densities and growth rates. Temperature steps of different sign changed the fluorescence polarization slightly in different directions. The phase shift of 4-h pulses (-5, -9, +7 degrees C) resulted in maximal phase advances of 4, 6, and 2 h, respectively. The phasing of the phase-response curves was identical in all these experiments, a finding not to be expected if the pulses act via the measured membrane properties. Pulses of drugs that change the fluorescence polarization (e.g., chlorpromazine and lidocaine) did not or only slightly phase-shift the circadian rhythm.

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