Phase-resetting action of light on the circadian activity rhythm of Rattus exulans

The phase resetting action of light on the circadian rhythm of locomotor activity has been examined in wild-caught Polynesian rats (Rattus exulans). Phase-response curves to 4-, 8-, and 16-h light pulses have been derived. All three curves conform to the generalization that pulses occurring during late subjective day and early subjective night produce delays, whereas advances occur in response to pulses coinciding with the late subjective night and early subjective day. Weak (type 1) phase resetting is observed in response to 4-h pulses and perhaps 8-h pulses, whereas strong (type 0) resetting apparently occurs in response to 16-h pulses. These data evidently constitute the first report of strong phase resetting in mammalian circadian rhythms. The phase relationship between an entrained activity rhythm and the light-dark cycle is dependent on the photoperiod and, in 24-h cycles, on the period difference between the rhythm and the zeitgeber. In longer zeitgeber cycles, activity onset is delayed by a direct masking effect of light. A primarily nonparametric action of light in natural entrainment is consistent with these data and with field observations.

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Reduced glucose availability attenuates circadian responses to light in mice

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1999.276.4.r1063 ◽

1999 ◽

Vol 276 (4) ◽

pp. R1063-R1070 ◽

Cited By ~ 14

Author(s):

Etienne Challet ◽

Susan Losee-Olson ◽

Fred W. Turek

Keyword(s):

Locomotor Activity ◽

Glucose Utilization ◽

Insulin Treatment ◽

Phase Shifts ◽

Constant Darkness ◽

Phase Resetting ◽

Light Pulses ◽

Subjective Night ◽

Saline Administration ◽

Glucose Availability

To test whether circadian responses to light are modulated by decreased glucose availability, we analyzed photic phase resetting of the circadian rhythm of locomotor activity in mice exposed to four metabolic challenges: 1) blockade of glucose utilization induced by 2-deoxy-d-glucose (2-DG), 2) fasting (food was removed for 30 h), 3) insulin administration, and 4) insulin treatment after fasting. In mice housed in constant darkness, light pulses applied during early subjective night induced phase delays of the rhythm of locomotor activity, whereas light pulses applied during late subjective night caused phase advances. There was an overall reduction of light-induced phase shifts, with a more pronounced effect for delays, in mice pretreated with 500 mg/kg ip 2-DG compared with mice injected with saline. Administration of glucose with 2-DG prevented the reduction of light-induced phase delays. Furthermore, phase delays were reduced in fed mice pretreated with 5 IU/kg sc insulin and in fasted mice injected with saline or insulin compared with control fed mice. These results show that circadian responses to light are reduced when brain glucose availability is decreased, suggesting a metabolic modulation of light-induced phase shifts.

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Photoperiod differentially modulates photic and nonphotic phase response curves of hamsters

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00456.2003 ◽

2004 ◽

Vol 286 (3) ◽

pp. R539-R546 ◽

Cited By ~ 32

Author(s):

J. A. Evans ◽

J. A. Elliott ◽

M. R. Gorman

Keyword(s):

Wheel Running ◽

Phase Response Curve ◽

Phase Shifts ◽

Phase Response ◽

Cycle Phase ◽

Phase Resetting ◽

Response Curves ◽

Syrian Hamsters ◽

Light Pulses ◽

Circadian Time

Circadian pacemakers respond to light pulses with phase adjustments that allow for daily synchronization to 24-h light-dark cycles. In Syrian hamsters, Mesocricetus auratus, light-induced phase shifts are larger after entrainment to short daylengths (e.g., 10 h light:14 h dark) vs. long daylengths (e.g., 14 h light:10 h dark). The present study assessed whether photoperiodic modulation of phase resetting magnitude extends to nonphotic perturbations of the circadian rhythm and, if so, whether the relationship parallels that of photic responses. Male Syrian hamsters, entrained for 31 days to either short or long daylengths, were transferred to novel wheel running cages for 2 h at times spanning the entire circadian cycle. Phase shifts induced by this stimulus varied with the circadian time of exposure, but the amplitude of the resulting phase response curve was not markedly influenced by photoperiod. Previously reported photoperiodic effects on photic phase resetting were verified under the current paradigm using 15-min light pulses. Photoperiodic modulation of phase resetting magnitude is input specific and may reflect alterations in the transmission of photic stimuli.

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Locomotor activity in the Namaqua rock mouse (Micaelamys namaquensis): entrainment by light manipulations

Canadian Journal of Zoology ◽

10.1139/cjz-2014-0161 ◽

2014 ◽

Vol 92 (12) ◽

pp. 1083-1091 ◽

Cited By ~ 6

Author(s):

I. van der Merwe ◽

N.C. Bennett ◽

A. Haim ◽

M.K. Oosthuizen

Keyword(s):

Locomotor Activity ◽

Activity Rhythm ◽

Light Cycle ◽

Nocturnal Activity ◽

Dark Cycle ◽

Subjective Night ◽

Activity Onset ◽

Role Of Light ◽

Constant Dark

The locomotor activity rhythms of wild-caught Namaqua rock mice (Micaelamys namaquensis (A. Smith, 1834)) were examined under four light-cycle regimes to quantitatively describe the daily expression of locomotor activity and to study the innate relationship between activity and the light–dark cycle. Activity was always significantly higher at night than during the day; we note four trends. (1) The LD1 light cycle (12 h light : 12 h dark) established a distinct light-entrained and strongly nocturnal activity rhythm (99.11% nocturnal activity). The activity onset was prompt (zeitgeber time (ZT) 12.2 ± 0.04) and activity continued without any prominent peaks or extended times of rest until the offset of activity at ZT 23.73 ± 0.08. (2) Evidence for the internal maintenance of locomotor activity was obtained from the constant dark cycle (DD) in which locomotor activity free ran (mean τ = 23.89 h) and 77.58% of the activity was expressed during the subjective night. (3) During re-entrainment (LD2; 12 h light : 12 h dark), a nocturnal activity rhythm was re-established (98.65% nocturnal activity). (4) The inversion of the light cycle (DL; 12 h dark : 12 h light) evoked a shift in activity that again revealed dark-induced locomotor activity (95.69% nocturnal activity). Females were consistently more active than males in all of the light cycles, but only under the DD and LD2 cycles were females significantly more active than males. Although this species is considered nocturnal from field observations, information regarding its daily expression of activity and the role of light in its entrainment is lacking. To the best of our knowledge, this study is the first to report quantitatively on the species’ daily rhythm of activity and to investigate its relationship to the light–dark cycle.

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Activity rhythm in High Arctic Svalbard ptarmigan (Lagopus mutus hyperboreus)

Canadian Journal of Zoology ◽

10.1139/z98-173 ◽

1998 ◽

Vol 76 (11) ◽

pp. 2031-2039 ◽

Cited By ~ 33

Author(s):

Eirik Reierth ◽

Karl-Arne Stokkan

Keyword(s):

Activity Rhythm ◽

Feeding Activity ◽

Phase Relationship ◽

High Arctic ◽

Oscillator Model ◽

The Sun ◽

Activity Time ◽

Intermittent Feeding ◽

Lagopus Mutus ◽

Activity Onset

Feeding activity was recorded in captive Svalbard ptarmigan (Lagopus mutus hyperboreus) under natural photoperiodic conditions at 70°N and 79°N. At 79°N, activity was intermittent and non-circadian in summer, when the sun was permanently above the horizon, and in midwinter, when the sun was permanently lower than 6° below the horizon. The intermittent feeding pattern was evident in summer at 70°N, whereas feeding activity in winter appeared to be entrained. In spring and autumn all birds were diurnal, with morning and evening bouts of feeding activity. The phase relationship between the onset or end of activity and the photoperiod showed marked changes, especially at 79°N, but in general, activity onset was more precise relative to twilight than activity end. At 79°N there was a sigmoidal relationship between activity time and photoperiod and activity time was longer in autumn than in spring at equal photoperiods. Based on our results, the activity pattern of Svalbard ptarmigan may be described in terms of a two-oscillator model, although a one-oscillator model cannot be excluded. The possibility is discussed that rhythmic feeding or food availability may act as a zeitgeber in addition to the light-dark cycle.

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Administering triazolam on a circadian basis entrains the activity rhythm of hamsters

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1989.256.3.r639 ◽

1989 ◽

Vol 256 (3) ◽

pp. R639-R645

Author(s):

O. Van Reeth ◽

F. W. Turek

Keyword(s):

Response Curve ◽

Wheel Running ◽

Phase Response Curve ◽

Activity Rhythm ◽

Phase Relationship ◽

Phase Shifts ◽

Phase Response ◽

Light Pulses ◽

Circadian Time ◽

Free Running

A single injection of the short-acting benzodiazepine, triazolam, can induce permanent phase shifts in the circadian rhythm of locomotor activity in free-running hamsters, with the direction and magnitude of the phase shifts being dependent on the circadian time of treatment. The shape of the "phase-response curve" to triazolam injections is totally different from that for light pulses. These findings raise the possibility that repeated injections of triazolam on a circadian basis might be capable of entraining the circadian pacemaker underlying the activity rhythm of hamsters and that the entrainment pattern might differ from that observed in animals entrained to light pulses. To test this hypothesis, blind hamsters received intraperitoneal injections of triazolam (or vehicle) every 23.34, 23.72, 24.00 or 24.66 h for 19-20 days, and the effect of these injections on the period of the rhythm of wheel-running behavior was determined during and after treatment. Repeated injections of 0.1 mg triazolam at these time intervals resulted in the entrainment of the activity rhythm in 36 of 40 animals, whereas 0 of 40 animals entrained to vehicle injections. Importantly, the phase relationship between triazolam injections and the circadian activity rhythm was dependent on the period of drug treatment and could be predicted from the phase-response curve to single injections of triazolam. These phase relationships are dramatically different from those observed between the activity rhythm and 1-h light pulses presented at similar circadian intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

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Phase response curves to light in young and old hamsters

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1991.261.2.r491 ◽

1991 ◽

Vol 261 (2) ◽

pp. R491-R495 ◽

Cited By ~ 13

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.

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Hippocampal CA1 pyramidal neurons exhibit type 1 phase-response curves and type 1 excitability

Journal of Neurophysiology ◽

10.1152/jn.00721.2012 ◽

2013 ◽

Vol 109 (11) ◽

pp. 2757-2766 ◽

Cited By ~ 16

Author(s):

Shuoguo Wang ◽

Maximilian M. Musharoff ◽

Carmen C. Canavier ◽

Sonia Gasparini

Keyword(s):

Bias Correction ◽

Pyramidal Neurons ◽

Time Lag ◽

Correction Method ◽

Resonant Peak ◽

Phase Resetting ◽

Response Curves ◽

Ca1 Pyramidal Neurons

Phase-resetting properties of neurons determine their functionality as integrators (type 1) vs. resonators (type 2), as well as their synchronization tendencies. We introduce a novel, bias-correction method to estimate the infinitesimal phase-resetting curve (iPRC) and confirm type 1 excitability in hippocampal pyramidal CA1 neurons in vitro by two independent methods. First, PRCs evoked using depolarizing pulses consisted only of advances, consistent with type 1. Second, the frequency/current (f/I) plots showed no minimum frequency, again consistent with type 1. Type 1 excitability was also confirmed by the absence of a resonant peak in the interspike interval histograms derived from the f/I data. The PRC bias correction assumed that the distribution of noisy phase resetting is truncated, because an input cannot advance a spike to a point in time before the input (the causal limit) and successfully removed the statistical bias for delays in the null PRC in response to zero-magnitude input by computing the phase resetting as the mean of the untruncated distribution. The PRC for depolarization peaked at late phases and decreased to zero by the end of the cycle, whereas delays observed in response to hyperpolarization increased monotonically. The bias correction did not affect this difference in shape, which was due instead to the causal limit obscuring the iPRC for depolarization but not hyperpolarization. Our results suggest that weak periodic hyperpolarizing drive can theoretically entrain CA1 pyramidal neurons at any phase but that strong excitation will preferentially phase-lock them with zero time lag.

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Photoperiod modifies circadian resetting responses in sparrows

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1986.251.6.r1156 ◽

1986 ◽

Vol 251 (6) ◽

pp. R1156-R1162 ◽

Cited By ~ 2

Author(s):

S. Binkley ◽

K. Mosher

Keyword(s):

Phase Shift ◽

Passer Domesticus ◽

Time Of Day ◽

Short Photoperiod ◽

Response Curves ◽

House Sparrows ◽

Time Profiles ◽

Light Pulses ◽

Subjective Night ◽

The Mean

Circadian responses to photoperiod were studied in house sparrows (Passer domesticus) by subjecting them to 4-h light pulses and measuring the subsequent phases of their circadian rhythms. The direction and magnitude of phase shifts in response to 4-h light pulses following pretreatment with light-dark cycles (LD) 16:8 or LD 8:16 varied with time of day; advances (3.4 h) occurred when pulses were imposed in the late subjective night on both groups of birds; delays (-2.1 h) occurred when the pulses were imposed in the early subjective night on the LD 8:16 birds. The time profiles for responses to light pulses that scanned 24 h (phase-response curves) were modified by long and short photoperiod. Short photoperiod 1) increased amplitude (1.7 h), 2) increased time from the prior lights-out to the peak of advances (6 h), and 3) decreased the mean phase shift (0.9 h).

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Effect of somatostatin on circadian rhythms of firing and 2-deoxyglucose uptake in rat suprachiasmatic slices

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1993.265.5.r1199 ◽

1993 ◽

Vol 265 (5) ◽

pp. R1199-R1204 ◽

Cited By ~ 2

Author(s):

T. Hamada ◽

S. Shibata ◽

A. Tsuneyoshi ◽

K. Tominaga ◽

S. Watanabe

Keyword(s):

Circadian Rhythm ◽

Vasoactive Intestinal Polypeptide ◽

Phase Changes ◽

Circadian Clocks ◽

Constant Darkness ◽

Phase Resetting ◽

Firing Activity ◽

Light Pulses ◽

Circadian Time

In mammals, the suprachiasmatic nucleus (SCN) of the hypothalamus appears to act as a circadian clock. The SCN vasoactive intestinal polypeptide-like immunoreactive neurons, which may act to mediate photic information in the SCN, receive input from neurons immunoreactive for somatostatin (SST). Therefore we investigated the role of SST as a transmitter for entrainment by analyzing the phase-resetting effect of SST on the circadian rhythm of SCN firing activity. Perfusion of SST increased 2-deoxyglucose uptake at circadian time (CT) 18, but not at CT6. A 1-h or 15-min treatment with SST produced phase delays when it was administered at CT13-14 and phase advances at CT22-23. Thus SST-induced phase changes are similar to those for light pulses to animals under constant darkness. The present findings suggest that SST is a transmitter for mediating information of entrainment to circadian clocks within the SCN.

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