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.

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.

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.

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.

Two families of phase-response curves characterize the resetting of the hamster circadian clock

1992 ◽  
Vol 262 (6) ◽  
pp. R1149-R1153 ◽  
Author(s):  
R. D. Smith ◽  
F. W. Turek ◽  
J. S. Takahashi
Keyword(s):  
Golden Hamster ◽  
Phase Response ◽  
Phase Shifting ◽  
Circadian Pacemaker ◽  
Test Statistics ◽  
Response Curves ◽  
Phase Response Curves ◽  
Light Pulses ◽  
Circular Test ◽  
The Common

Phase-response curves (PRCs) have been reported for a wide variety of agents that induce phase shifts in the circadian rhythm of locomotor activity in the golden hamster. Many of these PRCs appear to be quite similar to one another. Because of the important role that the interpretation of PRCs has played in understanding the dynamics of the mammalian circadian pacemaker, a review of PRCs for the golden hamster reported from 1964 to 1991 was conducted to systematically summarize the common characteristics among these PRCs. Plots of phases associated with the peak of the advance portions, or of phases associated with the transitions between the delay and advance portion of the PRCs, revealed bimodal distributions of PRCs 11-13 h apart. Mardia-Watson-Wheeler circular test statistics indicated that the PRCs were distributed as two distinct populations. PRCs were either characteristic of those for light pulses (L-PRCs), or of those for dark pulses (D-PRCs). Taken with anatomical and physiological evidence, these data suggest that either one or two final common pathways may exist to mediate the phase-shifting effects of different stimuli.

Phase response curves to light in young and old hamsters

1991 ◽  
Vol 261 (2) ◽  
pp. R491-R495 ◽  
Author(s):  
R. S. Rosenberg ◽  
P. C. Zee ◽  
F. W. Turek
Keyword(s):  
Activity Rhythm ◽  
Age Groups ◽  
Break Point ◽  
Phase Response ◽  
Response Curves ◽  
Phase Response Curves ◽  
Light Pulses ◽  
Age Related ◽  
Circadian Time ◽  
Free Running Period

The phase-shifting effects of 1-h light pulses on the circadian rhythm of locomotor activity were measured in young (less than 12 mo old) and old (greater than 16 mo old) hamsters. Phase response curves (PRCs) for both age groups showed an inactive region [approximately circadian time (CT) 0 through CT12], a delay region (CT12 through CT16), and an advance region (CT16 through CT24) as has been reported for young animals. Significant age group differences in the amplitude of phase shifts were measured, with older animals showing larger shifts limited to the region of the "break point" at CT16. The free-running period of the activity rhythm was measured before the first light pulse; age-related decreases of period length consistent with previous reports were measured. The findings indicate that the response of the circadian clock to the major environmental synchronizing agent, light, is different in old hamsters compared with young adults.

Robotics Application of a Method for Analytically Computing Infinitesimal Phase Response Curves

2020 ◽  
pp. 104-115
Author(s):  
Marshaun N. Fitzpatrick ◽  
Yangyang Wang ◽  
Peter J. Thomas ◽  
Roger D. Quinn ◽  
Nicholas S. Szczecinski
Keyword(s):  
Phase Response ◽  
Response Curves ◽  
Phase Response Curves
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