scholarly journals Bright light during lactation alters the functioning of the circadian system of adult rats

2000 ◽  
Vol 278 (1) ◽  
pp. R201-R208 ◽  
Author(s):  
M. M. Canal-Corretger ◽  
T. Cambras ◽  
J. Vilaplana ◽  
A. Díez-Noguera
Keyword(s):  
Motor Activity ◽  
Activity Rhythm ◽  
Bright Light ◽  
Circadian System ◽  
Constant Darkness ◽  
Adult Rats ◽  
Light Pulses ◽  
Circadian Time ◽  
Role Of Light

To examine the role of light in the maturation of the circadian pacemaker, twelve groups of rats were raised in different conditions of exposure to constant bright light (LL) during lactation: both duration and timing of LL were varied. We studied the motor activity rhythm of the rats after weaning, first under LL and then under constant darkness (DD). In DD, two light pulses [at circadian time 15 (CT15) and CT22] were applied to test the response of the pacemaker. Greater exposure to LL days during lactation increased the number of rhythmic animals and the amplitude of their motor activity rhythm in the LL stage and decreased the phase delay due to the light pulse at CT15. The timing of LL during lactation affected these variables too. Because the response of the adult to light depended on both the number and timing of LL days during lactation, the exposure to light at early stages may influence the development of the circadian system by modifying it structurally or functionally.

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

1993 ◽  
Vol 265 (5) ◽  
pp. R1199-R1204 ◽  
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.

Dissociation of motor activity circadian rhythm in rats after exposure to LD cycles of 4-h period

1997 ◽  
Vol 272 (1) ◽  
pp. R95-R102 ◽  
Author(s):  
J. Vilaplana ◽  
T. Cambras ◽  
A. Diez-Noguera
Keyword(s):  
Motor Activity ◽  
Activity Rhythm ◽  
Bright Light ◽  
Constant Light ◽  
Constant Darkness ◽  
Circadian Oscillators ◽  
Entrainment Process ◽  
Free Running ◽  
Anticipatory Activity ◽  
Degree Of Coupling

For > 30 days Wistar rats were subjected to six dark pulses per day (T4 cycles; 3 h light, 1 h dark) to study the possibility of dissociating their motor activity rhythm into distinct circadian components. Rats of both sexes were used, one-half of which were pinealectomized to examine the effect of the pineal gland on the entrainment process. Results show that when rats were maintained under T4 a 4-h rhythm in their motor activity was present. Rats showed anticipatory activity to dark phases, suggesting that the motor activity components are actually entrained to the external light/dark (LD) cycles. When rats were left under constant darkness after T4, some motor activity components coming from the dark phases free ran for several days with different circadian periods. This suggests that the motor activity pattern is generated by several circadian oscillators. Moreover, the free-running components of motor activity after T4 were more evident when T4 was applied after exposure to constant light than after exposure to constant darkness. These results support the hypothesis that the circadian system of the rat is formed by several circadian oscillators, whose degree of coupling depends on light conditions. In constant light, bright light may inhibit internal coupling within the system, making it subsequently more susceptible to the T4 cycles. No differences were observed between pinealectomized and sham-operated animals, although females were more sensitive to T4 cycles than males.

Manifestation of circadian rhythm under constant light depends on lighting conditions during lactation

1997 ◽  
Vol 272 (4) ◽  
pp. R1039-R1046 ◽  
Author(s):  
T. Cambras ◽  
M. M. Canal ◽  
A. Torres ◽  
J. Vilaplana ◽  
A. Diez-Noguera
Keyword(s):  
Circadian Rhythm ◽  
Motor Activity ◽  
Activity Rhythm ◽  
Bright Light ◽  
Constant Light ◽  
Continuous Illumination ◽  
Continuous Darkness ◽  
Adult Rats ◽  
Lighting Conditions ◽  
Variance Explained

Adult rats transferred to continuous illumination (LL) show a disruption of circadian rhythms, although the mechanisms underlying this effect are not yet well known. In previous experiments, we found that when rats were born and raised under LL they showed an ultradian pattern during the first 10 days after weaning, but afterward they generated a circadian rhythm that was maintained until adulthood. It was not clear whether this evolution was attributable to the influence of the rhythm of the mother or to the effect of constant light. Here, we have studied the motor activity rhythm of young rats maintained under LL after weaning, taking into account the conditions to which they were exposed during lactation [LL or continuous darkness (DD)]. To check the possible effect of the rhythm of the dam, on the day of delivery some of the dams were blinded, others were subjected to a restricted feeding schedule of 3 h/day, and the others were used as controls. For each rat, the period of the circadian rhythm and the percentage of variance explained by this rhythm were calculated. Results show that all rats maintained under LL during lactation expressed a circadian rhythm in their motor activity. However, rats maintained under DD during lactation did not. This effect did not seem to be dependent on the type of dam. These results suggest that the rhythm of the dams does not affect the manifestation of the rhythm of the pups and that the expression of circadian rhythmicity under constant bright light depends on the lighting conditions under which the animals were maintained during lactation, which could affect the development of the circadian pacemaker or the retina.

Gonadal hormones organize and modulate the circadian system of the rat

1981 ◽  
Vol 241 (1) ◽  
pp. R62-R66 ◽  
Author(s):  
H. E. Albers
Keyword(s):  
Testosterone Propionate ◽  
Wheel Running ◽  
Activity Rhythm ◽  
Gonadal Hormones ◽  
Circadian System ◽  
Female Rats ◽  
Constant Darkness ◽  
Before And After ◽  
Free Running ◽  
Free Running Period

The circadian wheel-running rhythms of gonadectomized adult male, female, and perinatally androgenized female rats, maintained in constant darkness, were examined before and after implantation of Silastic capsules containing cholesterol (C) or estradiol-17 beta (E). The free-running period of the activity rhythm (tau) before capsule implantation tended to be shorter in animals exposed to perinatal androgen. Administration of C did not reliably alter tau in any group. E significantly shortened tau in 100% of females injected with oil on day 3 of life. In females, injected with 3.5 micrograms testosterone propionate on day 3, and males, E shortened or lengthened tau, with the direction and magnitude of this change in tau inversely related to the length of the individual's pretreatment tau. These data indicate that the presence of perinatal androgen does not eliminate the sensitivity of the circadian system of the rat to estrogen, since estrogen alters tau in a manner that depends on its pretreatment length.

Disrupted circadian rhythms in VIP- and PHI-deficient mice

2003 ◽  
Vol 285 (5) ◽  
pp. R939-R949 ◽  
Author(s):  
Christopher S. Colwell ◽  
Stephan Michel ◽  
Jason Itri ◽  
Williams Rodriguez ◽  
J. Tam ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Wheel Running ◽  
Activity Rhythm ◽  
Activity Patterns ◽  
Circadian System ◽  
Diurnal Rhythms ◽  
Constant Darkness ◽  
Light Cycle ◽  
Wild Type ◽  
Deficient Mice

The related neuropeptides vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are expressed at high levels in the neurons of the suprachiasmatic nucleus (SCN), but their function in the regulation of circadian rhythms is unknown. To study the role of these peptides on the circadian system in vivo, a new mouse model was developed in which both VIP and PHI genes were disrupted by homologous recombination. In a light-dark cycle, these mice exhibited diurnal rhythms in activity which were largely indistinguishable from wild-type controls. In constant darkness, the VIP/PHI-deficient mice exhibited pronounced abnormalities in their circadian system. The activity patterns started ∼8 h earlier than predicted by the previous light cycle. In addition, lack of VIP/PHI led to a shortened free-running period and a loss of the coherence and precision of the circadian locomotor activity rhythm. In about one-quarter of VIP/PHI mice examined, the wheel-running rhythm became arrhythmic after several weeks in constant darkness. Another striking example of these deficits is seen in the split-activity patterns expressed by the mutant mice when they were exposed to a skeleton photoperiod. In addition, the VIP/PHI-deficient mice exhibited deficits in the response of their circadian system to light. Electrophysiological analysis indicates that VIP enhances inhibitory synaptic transmission within the SCN of wild-type and VIP/PHI-deficient mice. Together, the observations suggest that VIP/PHI peptides are critically involved in both the generation of circadian oscillations as well as the normal synchronization of these rhythms to light.

scholarly journals Short Neuropeptide F regulates the starvation mediated enhanced locomotor Activity in Drosophila

2019 ◽  
Author(s):  
Anna Geo ◽  
Himani Pathak ◽  
Anamika Elizabeth Kujur ◽  
Sreesha R Sudhakar ◽  
Nisha N Kannan
Keyword(s):  
Locomotor Activity ◽  
Circadian Clock ◽  
Internal Energy ◽  
Nutrient Availability ◽  
Activity Rhythm ◽  
Transcript Level ◽  
Constant Darkness ◽  
Starvation Resistance ◽  
Neuropeptide F

AbstractThe circadian clock regulates various behavioral, metabolic and physiological processes to occur at the most suitable time of the day. Internal energy stores and nutrient availability modulates the most apparent circadian clock mediated locmotor activity rhythm in Drosophila. Although previous studies unraveled the role of circadian clock in metabolism and activity rest rhythm, the precise pathway through which the circadian neuropeptidergic signaling regulates internal energy storage and the starvation-mediated increase in activity resembling foraging remains largely unclear. This study was aimed to elucidate the role of circadian neuropeptide, short neuropeptide F (sNPF) in triglyceride metabolism, starvation resistance and starvation-mediated increased locomotor activity in Drosophila. The results showed that snpf transcripts exhibits significant rhythmicity in wild type flies under 12:12 hour light-dark cycles (LD) and constant darkness (DD) whereas snpf transcript level in period null flies did not exhibit any significant rhythmicity under LD. Knockdown of sNPF in circadian clock neurons reduced the triglyceride level, starvation resistance and increased the starvation-mediated hyperactivity response after 24 hour of starvation. Further studies showed that knock down of sNPF receptors (sNPFR) expressed in insulin producing cells (IPC) increased the starvation resistance and reduced starvation-induced hyperactivity response after 24 hour of starvation. Collectively, our results suggest that transcriptional oscillation of snpf mRNA is endogenously controlled by the circadian clock and elucidate the role of sNPF in modulating locomotor activity in accordance with the nutrient availability in Drosophila.

Melatonin administration entrains female rat activity rhythms in constant darkness but not in constant light

1988 ◽  
Vol 255 (2) ◽  
pp. R237-R242
Author(s):  
E. M. Thomas ◽  
S. M. Armstrong
Keyword(s):  
Estrous Cycle ◽  
Activity Rhythm ◽  
Onset Time ◽  
Circadian System ◽  
Female Rats ◽  
Male Rats ◽  
Constant Darkness ◽  
Female Rat ◽  
Continuous Darkness ◽  
Activity Rhythms

In female rats the luteinizing hormone (LH) is timed by the circadian system and is followed by a display of intense, estrogen-induced running behavior. This proestrous running on the night of ovulation can be used as a marker of the estrous cycle. Entrainment of the mammalian circadian system by exogenous melatonin (MT) has been demonstrated only in the activity rhythms of male rats. The present experiments were designed to study the effect of daily MT injections on activity rhythms and proestrous running of female rats in 1) continuous dim white light (LL) and 2) continuous darkness (DD). In LL, MT injections (50 micrograms/kg or 1 mg/kg) had no discernible effect on activity rhythms. In DD, four of the six MT-treated rats (100 micrograms/kg) entrained to the injection, and a fifth animal showed phase advances in its activity rhythm when onset of activity passed through injection time. The sixth animal was not injected with MT at activity onset time. None of the six control animals showed either effect. MT had no effect on the length of the estrous cycle. Thus MT injections can entrain circadian rhythms of activity and proestrous running in female rats in DD but not in LL.

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

2014 ◽  
Vol 92 (12) ◽  
pp. 1083-1091 ◽  
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.

scholarly journals A Mathematical Model to Characterize the Role of Light Adaptation in Mammalian Circadian Clock

2021 ◽  
Vol 8 ◽  
Author(s):  
Yuzeng Shi ◽  
Yu Liu ◽  
Ling Yang ◽  
Jie Yan
Keyword(s):  
Mathematical Model ◽  
Circadian Clock ◽  
Light Adaptation ◽  
Light Stimulus ◽  
Circadian System ◽  
Jet Lag ◽  
Short Term ◽  
Adaptation Mechanism ◽  
Role Of Light

In response to a light stimulus, the mammalian circadian clock first dramatically increases the expression of Per1 mRNA, and then drops to a baseline even when light persists. This phenomenon is known as light adaptation, which has been experimentally proven to be related to the CRTC1-SIK1 pathway in suprachiasmatic nucleus (SCN). However, the role of this light adaptation in the circadian rhythm remains to be elucidated. To reveal the in-depth function of light adaptation and the underlying dynamics, we proposed a mathematical model for the CRTC1-SIK1 network and coupled it to a mammalian circadian model. The simulation result proved that the light adaptation is achieved by the self-inhibition of the CRTC1/CREB complex. Also, consistently with experimental observations, this adaptation mechanism can limit the phase response to short-term light stimulus, and it also restricts the rate of the phase shift in a jet lag protocol to avoid overly rapid re-entrainment. More importantly, this light adaptation is predicted to prevent the singularity behavior in the cell population, which represents the abolishment of circadian rhythmicity due to desynchronization of oscillating cells. Furthermore, it has been shown to provide refractoriness to successive stimuli with short gap. Therefore, we concluded that the light adaptation generated by the CRTC1-SIK1 pathway in the SCN provides a robust mechanism, allowing the circadian system to maintain homeostasis in the presence of light perturbations. These results not only give new insights into the dynamics of light adaptation from a computational perspective but also lead us to formulate hypotheses about the related physiological significance.

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

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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