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.

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.

Reduced glucose availability attenuates circadian responses to light in mice

1999 ◽  
Vol 276 (4) ◽  
pp. R1063-R1070 ◽  
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.

Photoperiod differentially modulates photic and nonphotic phase response curves of hamsters

2004 ◽  
Vol 286 (3) ◽  
pp. R539-R546 ◽  
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.

Knockdown of clock genes in the suprachiasmatic nucleus blocks prolactin surges and alters FRA expression in the locus coeruleus of female rats

2007 ◽  
Vol 293 (5) ◽  
pp. E1325-E1334 ◽  
Author(s):  
Maristela O. Poletini ◽  
De'Nise T. McKee ◽  
Jessica E. Kennett ◽  
Jamie Doster ◽  
Marc E. Freeman
Keyword(s):  
Circadian Rhythm ◽  
Locus Coeruleus ◽  
Suprachiasmatic Nucleus ◽  
Clock Genes ◽  
Random Sequence ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Gene Expressions ◽  
Circadian Time

The nature of the circadian signal from the suprachiasmatic nucleus (SCN) required for prolactin (PRL) surges is unknown. Because the SCN neuronal circadian rhythm is determined by a feedback loop of Period (Per) 1, Per2, and circadian locomotor output cycles kaput ( Clock) gene expressions, we investigated the effect of SCN rhythmicity on PRL surges by disrupting this loop. Because lesion of the locus coeruleus (LC) abolishes PRL surges and these neurons receive SCN projections, we investigated the role of SCN rhythmicity in the LC neuronal circadian rhythm as a possible component of the circadian mechanism regulating PRL surges. Cycling rats on proestrous day and estradiol-treated ovariectomized rats received injections of antisense or random-sequence deoxyoligonucleotide cocktails for clock genes ( Per1, Per2, and Clock) in the SCN, and blood samples were taken for PRL measurements. The percentage of tyrosine hydroxylase-positive neurons immunoreactive to Fos-related antigen (FRA) was determined in ovariectomized rats submitted to the cocktail injections and in a 12:12-h light:dark (LD) or constant dark (DD) environment. The antisense cocktail abolished both the proestrous and the estradiol-induced PRL surges observed in the afternoon and the increase of FRA expression in the LC neurons at Zeitgeber time 14 in LD and at circadian time 14 in DD. Because SCN afferents and efferents were probably preserved, the SCN rhythmicity is essential for the magnitude of daily PRL surges in female rats as well as for LC neuronal circadian rhythm. SCN neurons therefore determine PRL secretory surges, possibly by modulating LC circadian neuronal activity.

Circadian rhythms of dopamine in mouse retina: The role of melatonin

2002 ◽  
Vol 19 (5) ◽  
pp. 593-601 ◽  
Author(s):  
SUSAN E. DOYLE ◽  
MICHAEL S. GRACE ◽  
WILSON McIVOR ◽  
MICHAEL MENAKER
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
High Performance ◽  
Mouse Retina ◽  
Constant Darkness ◽  
Dark Cycle ◽  
Melatonin Synthesis ◽  
Dopamine Content ◽  
C3h Mice

Both dopamine and melatonin are important for the regulation of retinal rhythmicity, and substantial evidence suggests that these two substances are mutually inhibitory factors that act as chemical analogs of day and night. A circadian oscillator in the mammalian retina regulates melatonin synthesis. Here we show a circadian rhythm of retinal dopamine content in the mouse retina, and examine the role of melatonin in its control. Using high-performance liquid chromatography (HPLC), we measured levels of dopamine and its two major metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in retinas of C3H+/+ mice (which make melatonin) and C57BL/6J mice that are genetically incapable of melatonin synthesis. In a light/dark cycle both strains of mice exhibited daily rhythms of retinal dopamine, DOPAC, and HVA content. However, after 10 days in constant darkness (DD), a circadian rhythm in dopamine levels was present in C3H, but not in C57 mice. C57 mice given ten daily injections of melatonin in DD exhibited a robust circadian rhythm of retinal dopamine content whereas no such rhythm was present in saline-injected controls. Our results demonstrate that (1) a circadian clock generates rhythms of dopamine content in the C3H mouse retina, (2) mice lacking melatonin also lack circadian rhythms of dopamine content, and (3) dopamine rhythms can be generated in these mice by cyclic administration of exogenous melatonin. Our results also indicate that circadian rhythms of retinal dopamine depend upon the rhythmic presence of melatonin, but that cyclic light can drive dopamine rhythms in the absence of melatonin.

Entrainment of the circadian rhythm from the eye of Aplysia: role of serotonin

1982 ◽  
Vol 242 (3) ◽  
pp. R326-R332
Author(s):  
G. Corrent ◽  
A. Eskin ◽  
I. Kay
Keyword(s):  
Circadian Rhythm ◽  
Phase Shift ◽  
Transmitter Release ◽  
Response Curve ◽  
Phase Shifts ◽  
Phase Response ◽  
Phase Shifting ◽  
Response Curves ◽  
Light Pulses

The finding that serotonin (5-HT) treatments as short as 1.5 h in duration produce phase shifts in a circadian rhythm from the isolated eye of Aplysia suggested that release of 5-HT was part of an ocular entrainment pathway. Since light cycles entrain this rhythm, we compared phase shifting by 5-HT and by light. The similarity in the shapes of the phase-response curves for 5-HT and light pulses indicates that 5-HT treatments are capable of entraining the rhythm. Also, "skeleton" 5-HT treatments phase shift as well as continuous 5-HT treatments. However, 5-HT does not appear to mediate the phase shifts produced by light, since 1) treatments that should block transmitter release do not change the phase shifts produced by light pulses; 2) the response curves of 5-HT and light pulses are displaced by 12 h relative to one another on the phase axis of the response curve; and 3) light-induced phase shifts are apparent almost immediately, whereas 5-HT-induced phase shifts become evident only about 24 h after 5-HT treatment. The eye appears to contain two independent entrainment pathways, one for light and one utilizing 5-HT.

scholarly journals Propofol Anesthesia Significantly Alters Plasma Blood Levels of Melatonin in Rats

2010 ◽  
Vol 112 (2) ◽  
pp. 333-337 ◽  
Author(s):  
Garance Dispersyn ◽  
Laure Pain ◽  
Yvan Touitou
Keyword(s):  
Circadian Rhythm ◽  
Activity Rhythm ◽  
Blood Levels ◽  
Light Conditions ◽  
Melatonin Secretion ◽  
Blood Samples ◽  
Circadian Time ◽  
Normal Light ◽  
Rest Activity

Background General anesthesia combined with surgery has been shown to decrease the nocturnal peak of melatonin in patients. However, the role of anesthesia itself on melatonin secretion remains unknown. We previously showed that anesthesia induced by propofol modifies the circadian time structure in both rats and humans and phase advances the circadian rest-activity rhythm in rats. In this study, we examined the secretion of melatonin during 24 h after a 30-min propofol anesthesia in rats. Methods Rats were exposed to 12-h light/12-h dark alteration conditions and anesthetized with propofol (120 mg/kg intraperitoneally) around their peak of melatonin secretion (Zeitgeber time 16). Trunk blood samples were collected at seven subsequent Zeitgeber times to assess the effects of propofol on circadian melatonin secretion. Results Propofol modifies the peripheral melatonin by significantly decreasing its concentration ( approximately 22-28%) during the immediate 3 h after the wake up from anesthesia and then significantly increasing melatonin secretion 20 h after anesthesia ( approximately 38%). Cosinor analysis suggests that propofol induces a phase advance of the circadian secretion of peripheral melatonin. Conclusions The results demonstrate the disturbing effects of propofol anesthesia on the circadian rhythm of plasma melatonin in rats under normal light conditions. These results parallel the desynchronization of the circadian rhythms of locomotor activity and temperature previously observed after propofol anesthesia.

Oscillator control of cell division in Euglena: cyclic AMP oscillations mediate the phasing of the cell division cycle by the circadian clock

1993 ◽  
Vol 104 (4) ◽  
pp. 1163-1173 ◽  
Author(s):  
I.A. Carre ◽  
L.N. Edmunds
Keyword(s):  
Cell Division ◽  
Cyclic Amp ◽  
Cell Division Cycle ◽  
Circadian Oscillator ◽  
Constant Darkness ◽  
Rapid Loss ◽  
Subjective Night ◽  
Circadian Time ◽  
Pharmacological Studies

The achlorophyllous ZC strain of Euglena gracilis exhibits a circadian rhythm of cell division in constant darkness (DD). Mitosis occurs during a restricted part of the circadian cycle, corresponding to the dark intervals in a light-dark cycle comprising 12 h of light and 12 h of darkness. We have demonstrated that division-phased cultures also exhibit bimodal, circadian changes of cyclic AMP level. Maximum cyclic AMP levels occurred at the beginning of the light period (CT (circadian time) 00–02), and at the beginning of darkness (CT 12–14). These variations persisted in cultures that had been transferred into DD and appeared to be under the control of the circadian oscillator rather than to be cell division cycle (CDC)-dependent, since they continued in cultures that had reached the stationary phase of growth. In the experiments reported in this paper, we tested for the possible role of this periodic cyclic AMP signal in the generation of cell division rhythmicity by examining the effects of exogenous cyclic AMP signals and of forskolin, which permanently increased the cyclic AMP level, on the cell division rhythm. Perturbations of the cyclic AMP oscillation by exogenous cyclic AMP resulted in the temporary uncoupling of the CDC from the circadian timer. The addition of cyclic AMP during the subjective day resulted in delays (up to 9 h) of the next synchronous division step. In contrast, mitosis was stimulated when cyclic AMP was administered in the middle of the subjective night. Measurement of the DNA content of cells by flow cytometry indicated that cyclic AMP injected at CT 06–08 delayed progression through S phase, and perhaps also through mitosis. When added at CT 18–20, cyclic AMP accelerated the G2/M transition. The circadian oscillator was not perturbed by the addition of exogenous cyclic AMP: the division rhythm soon returned to its original phase. On the other hand, the permanent elevation of cyclic AMP levels in the presence of forskolin induced a rapid loss of cell division rhythmicity. These findings are consistent with the hypothesis that cyclic AMP acts downstream from the oscillator and that the cyclic AMP oscillation is an essential component of the signaling pathway for the control of the CDC by the circadian oscillator. The receptors for cyclic AMP in Euglena have been shown to be two cyclic AMP-dependent kinases (cPKA and cPKB). Pharmacological studies using cyclic AMP analogs suggested that cPKA mediates cyclic AMP effects during the subjective day, and cPKB during the subjective night.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Altered Light Sensitivity of Circadian Clock in Shank3+/– Mouse

2021 ◽  
Vol 15 ◽  
Author(s):  
Javier Alamilla ◽  
Yazmín Ramiro-Cortés ◽  
Adriana Mejía-López ◽  
José-Luis Chavez ◽  
Dulce Olivia Rivera ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Circadian Clock ◽  
Neurodevelopmental Disorder ◽  
Red Light ◽  
Bright Light ◽  
Light Sensitivity ◽  
Autism Spectrum ◽  
Constant Darkness ◽  
Light Pulses ◽  
Immunohistochemical Techniques

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairment in communication and social interaction, repetitive or stereotypical behaviors, altered sensory perception, and sleep disorders. In general, the causes of ASD remain unknown, but in Phelan–McDermid syndrome, it is known that the disorder is related to the haploinsufficiency of the Shank3 gene. We used an autism model with compromised glutamatergic signaling, the Shank3+/– mouse, to study the circadian rhythm architecture of locomotion behavior and its entrainment to light. We also analyzed the synapse between the retinohypothalamic tract (RHT) and the suprachiasmatic nucleus (SCN), employing tract tracing and immunohistochemical techniques. We found that Shank3+/– mice were not impaired in the SCN circadian clock, as indicated by a lack of differences between groups in the circadian architecture in entrained animals to either long or short photoperiods. Circadian rhythm periodicity (tau) was unaltered between genotypes in constant darkness (DD, dim red light). Similar results were obtained in the re-entrainment to shifts in the light–dark cycle and in the entrainment to a skeleton photoperiod from DD. However, Shank3+/– mice showed larger phase responses to light pulses, both delays and advances, and rhythm disorganization induced by constant bright light. Immunohistochemical analyses indicated no differences in the RHT projection to the SCN or the number of SCN neurons expressing the N-methyl-D-aspartate (NMDA) receptor subunit NR2A, whereas the Shank3+/– animals showed decreased c-Fos induction by brief light pulses at CT14, but increased number of vasoactive intestinal polypeptide (VIP)-positive neurons. These results indicate alterations in light sensitivity in Shank3+/– mice. Further studies are necessary to understand the mechanisms involved in such increased light sensitivity, probably involving VIP neurons.

The Possible Role of Prolactin in the Circadian Rhythm of Leptin Secretion in Male Rats

2000 ◽  
Vol 224 (3) ◽  
pp. 152-158 ◽  
Author(s):  
C. A. Mastronardi ◽  
A. Walczewska ◽  
W. H. Yu ◽  
S. Karanth ◽  
A. F. Parlow ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Male Rats
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