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Hagenauer MH, Ku JH, Lee TM. Chronotype changes during puberty depend on gonadal hormones in the slow-developing rodent, Octodon degus. Horm Behav 2011; 60:37-45. [PMID: 21316365 PMCID: PMC3112253 DOI: 10.1016/j.yhbeh.2011.02.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 02/03/2011] [Accepted: 02/03/2011] [Indexed: 11/28/2022]
Abstract
During puberty, human adolescents develop a later chronotype, exhibiting a delay in the timing of rest and activity as well as other daily physiological rhythms. The purpose of this study was to determine whether similar changes in chronotype occur during puberty in a laboratory rodent species, and, if so, to determine whether they are due to pubertal hormones acting on the circadian timekeeping system. To test this hypothesis, we carefully tracked daily activity rhythms across puberty in the slow-developing rodent Octodon degus. We confirmed that male degus showed a large reorganization of activity rhythms that correlated with secondary sex development during puberty, including a loss of bimodality and a 3-5 h phase-advance. Similar to humans, this circadian reorganization showed distinct sex differences, with females showing little change during puberty in two separate experiments. Prepubertal gonadectomy (GDX) eliminated the changes, whereas SHAM gonadectomy had little impact. Therefore, gonadal hormones are likely to play a role in pubertal changes in chronotype in this rodent species. Using evidence from a variety of species, including our recent studies in the rat, we conclude that chronotype changes during puberty are a well-demonstrated phenomenon in mammals.
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Zeman M, Herichová I. Circadian melatonin production develops faster in birds than in mammals. Gen Comp Endocrinol 2011; 172:23-30. [PMID: 21199656 DOI: 10.1016/j.ygcen.2010.12.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 12/24/2010] [Indexed: 11/17/2022]
Abstract
The development of circadian rhythmicity of melatonin biosynthesis in the pineal gland starts during embryonic period in birds while it is delayed to the postnatal life in mammals. Daily rhythms of melatonin in isolated pinealocytes and in intact pineal glands under in vivo conditions were demonstrated during the last third of embryonic development in chick embryos, with higher levels during the dark (D) than during the light (L) phase. In addition to the LD cycle, rhythmic temperature changes with the amplitude of 4.5°C can entrain rhythmic melatonin biosynthesis in chick embryos, with higher concentrations found during the low-temperature phase (33.0 vs 37.5°C). Molecular clockwork starts to operate during the embryonic life in birds in line with the early development of melatonin rhythmicity. Expression of per2 and cry genes is rhythmic at least at day 16 and 18, respectively, and the circadian system operates in a mature-like manner soon after hatching. Rhythmic oscillations are detected earlier in the central oscillator (the pineal gland) than in the peripheral structures, reflecting the synchronization of individual cells which is necessary for detection of the rhythm. The early development of the circadian system in birds reflects an absence of rhythmic maternal melatonin which in mammals synchronizes physiological processes of offspring. Developmental consequences of modified development of circadian system for its stability later in development are not known and should be studied.
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Affiliation(s)
- Michal Zeman
- Department of Animal Physiology and Ethology, Faculty of Natural Sciences, Comenius University, Bratislava, Slovak Republic.
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53
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Matejů K, Sumová A, Bendová Z. Expression and light sensitivity of clock genes Per1 and Per2 and immediate-early gene c-fos within the retina of early postnatal Wistar rats. J Comp Neurol 2010; 518:3630-44. [PMID: 20589906 DOI: 10.1002/cne.22421] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Mammalian retina contains a circadian clock that is composed of components similar to those of the master circadian clock within the suprachiasmatic nuclei of the hypothalamus. The aim of the present study was to elucidate whether, when, and where the transcripts of the clock genes Per1 and Per2 and the immediate early gene c-fos are spontaneously expressed and/or induced by light in the newborn rat retina. At postnatal day 1 (P1), P3, P5, and P10, Wistar rat pups were released into constant darkness, and a 30-minute light pulse was administered during the subjective day or during the first or second part of subjective night. Gene expression was determined 30 minutes, 1 hour, 2 hours, and 4 hours after the light pulse by in situ hybridization followed by emulsion autoradiography. Endogenous expression of Per1 was detected in the neuroblastic retina, and Per2 expression was detected in the inner part of the neuroblastic retina from birth. Light pulses induced c-fos expression in ganglion cells from P1. Until P5, the cells were localized in the dorsal part of the retina, but, at P10, they were already distributed across the entire retinal circumference. Light pulses also induced the expression of c-fos and Per1 in the retinal pigment epithelium until P3, but not afterward. Expression of the Per2 gene was not photoresponsive until P10. These data demonstrate that the rat retina is light-sensitive immediately after birth. During early postnatal development, the spatial distribution of spontaneous and light-induced gene expression within the retinal layers changes gradually.
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Affiliation(s)
- Kristýna Matejů
- Department of Neurohumoral Regulations, Institute of Physiology, Academy of Sciences of the Czech Republic v.v.i., Prague 14220, Czech Republic
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54
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Schrader JA, Nunez AA, Smale L. Changes in and dorsal to the rat suprachiasmatic nucleus during early pregnancy. Neuroscience 2010; 171:513-23. [PMID: 20807562 DOI: 10.1016/j.neuroscience.2010.08.057] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/07/2010] [Accepted: 08/26/2010] [Indexed: 01/25/2023]
Abstract
Circadian rhythms in behavior and physiology change as female mammals transition from one reproductive state to another. The mechanisms responsible for this plasticity are poorly understood. The suprachiasmatic nucleus (SCN) of the hypothalamus contains the primary circadian pacemaker in mammals, and a large portion of its efferent projections terminate in the ventral subparaventricular zone (vSPZ), which also plays important roles in rhythm regulation. To determine whether these regions might mediate changes in overt rhythms during early pregnancy, we first compared rhythms in Fos and Per2 protein expression in the SCN and vSPZ of diestrous and early pregnant rats maintained in a 12:12-h light/dark (LD) cycle. No differences in the Fos rhythm were seen in the SCN core, but in the SCN shell, elevated Fos expression was maintained throughout the light phase in pregnant, but not diestrous, rats. In the vSPZ, the Fos rhythm was bimodal in diestrous rats, but this rhythm was lost in pregnant rats. Peak Per2 expression was phase-advanced by 4 h in the SCN of pregnant rats, and some differences in Per2 expression were found in the vSPZ as well. To determine whether differences in Fos expression were due to altered responsivity to light, we next characterized light-induced Fos expression in the SCN and vSPZ of pregnant and diestrous rats in the mid-subjective day and night. We found that the SCN core of the two groups responded in the same way at each time of day, whereas the rhythm of Fos responsivity in the SCN shell and vSPZ differed between diestrous and pregnant rats. These results indicate that the SCN and vSPZ are functionally re-organized during early pregnancy, particularly in how they respond to the photic environment. These changes may contribute to changes in overt behavioral and physiological rhythms that occur at this time.
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Affiliation(s)
- J A Schrader
- Department of Zoology, Michigan State University, East Lansing, MI 48824, USA
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55
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Weinert D. Circadian temperature variation and ageing. Ageing Res Rev 2010; 9:51-60. [PMID: 19619672 DOI: 10.1016/j.arr.2009.07.003] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 07/09/2009] [Accepted: 07/10/2009] [Indexed: 01/19/2023]
Abstract
In the present paper, an attempt is made to summarize current knowledge concerning the daily body temperature rhythm and its age-dependent alterations. Homeostatic and circadian control mechanisms are considered. Special attention is paid to the circadian system, as the mechanisms of autonomic control are the topic of another contribution to this special issue. Also, the interactions of the core body temperature rhythm with other circadian functions are discussed in detail as they constitute an essential part of the internal temporal order of living systems and thus guarantee their optimal functioning. In the second part of the paper, age-dependent changes in the circadian body temperature rhythm and their putative causes, considering circadian and homeostatic components, are described. Consequences for health and fitness and some possibilities to prevent adverse effect are mentioned in the final section.
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Affiliation(s)
- Dietmar Weinert
- Institute of Biology/Zoology, Martin-Luther-University Halle-Wittenberg, Domplatz 4, D-06108 Halle, Germany.
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56
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Domínguez G, Ramírez M, Arechaga G. Day–Night Differences in Membrane‐Bound Pyroglutamyl‐2‐Naphthylamide‐Hydrolyzing Activity in Rat Hypothalamus, Pituitary, and Retina. Chronobiol Int 2009; 23:767-77. [PMID: 16887747 DOI: 10.1080/07420520600865582] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Membrane-bound pyroglutamyl-2-naphthylamide-hydrolyzing enzyme activity was analyzed fluorometrically in the anterior hypothalamus, pituitary, and retina of adult male rats to investigate day-night differences. Six groups (n=6 per group) were assessed--three during the light span and three during the dark span--under a standard 12 h-12 h light-dark cycle (light on from 07:00 to 19:00 h) and controlled temperature environment, with food and water available ad libitum. In the hypothalamus, enzyme activity levels were higher for time points of the dark than the light period. In contrast, the pituitary and retina exhibited the highest levels at the time points of the light period. The pituitary and retina also exhibited significant differences between the clock-hour means of the light period. Day-night differences in membrane-bound pyroglutamyl-2-naphthylamide-hydrolyzing activity may reflect differences in its susceptible endogenous substrates.
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Affiliation(s)
- Germán Domínguez
- Dpto. CC de la Salud, Area de Fisiología, Facultad de CC Experimentales, Jaén, Spain
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57
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Portaluppi F. Consistency and Accuracy of the Medical Subject Headings® Thesaurus for Electronic Indexing and Retrieval of Chronobiologic References. Chronobiol Int 2009; 24:1213-29. [DOI: 10.1080/07420520701791570] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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58
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Matějů K, Bendová Z, El-Hennamy R, Sládek M, Sosniyenko S, Sumová A. Development of the light sensitivity of the clock genesPeriod1andPeriod2, and immediate-early genec-foswithin the rat suprachiasmatic nucleus. Eur J Neurosci 2009; 29:490-501. [DOI: 10.1111/j.1460-9568.2009.06609.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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El-Hennamy R, Mateju K, Bendová Z, Sosniyenko S, Sumová A. Maternal control of the fetal and neonatal rat suprachiasmatic nucleus. J Biol Rhythms 2008; 23:435-44. [PMID: 18838609 DOI: 10.1177/0748730408322635] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The molecular clockwork underlying the generation of circadian rhythmicity within the suprachiasmatic nucleus (SCN) develops gradually during ontogenesis. The authors' previous work has shown that rhythms in clock gene expression in the rat SCN are not detectable at embryonic day (E) 19, start to form at E20 and develop further via increasing amplitude until postnatal day (P) 10. The aim of the present work was to elucidate whether and how swiftly the immature fetal and neonatal molecular SCN clocks can be reset by maternal cues. Pregnant rats maintained under a light-dark (LD) regimen with 12 h of light and 12 h of darkness were exposed to a 6-h delay of the dark period and released into constant darkness at different stages of the fetal SCN development. Adult rats maintained under the same LD regimen were exposed to an identical shifting procedure. Daily rhythms in spontaneous c-fos, Avp, Per1, and Per2 expression were examined within the adult and newborn SCN by in situ hybridization. Exposure of adult rats to the shifting procedure induced a significant phase delay of locomotor activity within 3 days after the phase shift as well as a delay in the rhythms of c-fos and Avp expression within 3 days and Per1 and Per2 expression within 5 days. Exposure of pregnant rats to the shifting procedure at E18, but not at E20, delayed the rhythm in c-fos and Avp expression in the SCN of newborn pups at P0-1. The shifting procedure at E20 did, however, induce a phase delay of Per1 and Per2 expression rhythms at P3 and P6. Hence, 5 days were necessary for phase-shifting the pups' SCN clock by maternal cues, be it the interval between E18 and P0-1 or the interval between E20 and P3, while only 3 days were necessary for phase-shifting the maternal SCN by photic cues. These results demonstrate that the SCN clock is capable of significant phase shifts at fetal developmental stages when no or very faint molecular oscillations can be detected.
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Affiliation(s)
- Rehab El-Hennamy
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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60
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Seron-Ferre M, Valenzuela GJ, Torres-Farfan C. Circadian clocks during embryonic and fetal development. ACTA ACUST UNITED AC 2007; 81:204-14. [PMID: 17963275 DOI: 10.1002/bdrc.20101] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Circadian rhythmicity is a fundamental characteristic of organisms, which helps ensure that vital functions occur in an appropriate and precise temporal sequence and in accordance with cyclic environmental changes. Living beings are endowed with a system of biological clocks that measure time on a 24-hr basis, termed the circadian timing system. In mammals, the system is organized as a master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus, commanding peripheral clocks located in almost every tissue of the body. At the cell level, interlocking transcription/translation feedback loops of the genes Bmal-1, Clock, Per1-2, and Cry1-2, named clock genes, and their protein products results in circadian oscillation of clock genes and of genes involved in almost every cellular function. During gestation, the conceptus follows a complex and dynamic program by which it is simultaneously fit to develop and live in a circadian environment provided by its mother and to prepare for the very different environment that it will experience after birth. It has been known for a number of years that the mother tells the fetus the time of day and season of the year, and that the fetus uses this information to set the phase of fetal and neonatal circadian rhythms. There is evidence that the maternal rhythm of melatonin is one of the time signals to the fetus. In the last few years, the study of the development of the circadian system has turned to the investigation of the oscillatory expression of clock genes and their possible role in development, and to answering questions on the organization of the fetal circadian system. Emerging evidence shows that clock genes are expressed in the oocyte and during early and late development in embryo/fetal organs in the rat and in a fetal primate. The data available raise the intriguing possibility that the fetal SCN and fetal tissues may be peripheral clocks commanded by separate maternal signals. The rapid methodological and conceptual advances on chronobiology may help to unravel how the developing embryo and fetus faces time in this plastic period of life.
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Affiliation(s)
- Maria Seron-Ferre
- Programa de Fisiopatología, Instituto de Ciencias Biomédicas (ICBM) Facultad de Medicina, Universidad de Chile, Santiago, Chile.
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61
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Kaeffer B, des Robert C, Alexandre-Gouabau MC, Pagniez A, Legrand A, Amarger V, Küster A, Piloquet H, Champ M, le Huërou-Luron I, Rozé JC. Recovery of exfoliated cells from the gastrointestinal tract of premature infants: a new tool to perform "noninvasive biopsies?". Pediatr Res 2007; 62:564-9. [PMID: 17805197 DOI: 10.1203/pdr.0b013e318155a402] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To gain insight into specific gene expression in the gastrointestinal (GI) tract of preterm infants, we adapted a method to isolate exfoliated epithelial cells. Gastric residual fluid aspirates (n = 89) or stool samples (n = 10) were collected from 96 neonates (gestational age, 24-36 wk). Cells were characterized by microscopic observation, cytokeratin-18 immunodetection, and expression of transcripts. The human origin of cellular DNA was confirmed by amplification of specific X and Y chromosome sequences. Isolation yielded 100-500 cells per sample for gastric aspirates (n = 8) and 10-20 cells for fecal samples (n = 5). Epithelial origin was confirmed by immunodetection of cytokeratin 18. Analyses of reverse transcribed products, using two independent methods, from 15 gastric fluid and two stool samples showed that 18S-rRNA and transcripts of beta-actin, glyceraldehyde-3-phosphate dehydrogenase (gapdh), and period1 were in quantities corresponding to at least 10 cells. On 59 aspirates, we found beta-actin transcripts (all but one), cytokeratin 18 (eight positive of eight samples), SLC26-A7-1 (13 positive of 19 samples), period2 (17 positive of 17 samples), and clock (25 positive of 26 samples). Exfoliated cells can be recovered from gastric aspirates and fecal samples and serve as a tool to investigate the impact of therapeutic and nutritional regimens on the maturation of GI functions.
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Affiliation(s)
- Bertrand Kaeffer
- UMR-1280, Physiologie des Adaptations Nutritionnelles, F-44093 Nantes Cedex 1, France.
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62
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Gerstner JR, Landry CF. The zinc-binding protein chordc1 undergoes complex diurnal changes in mRNA expression during mouse brain development. Neurochem Res 2007; 32:241-50. [PMID: 17253150 PMCID: PMC6528676 DOI: 10.1007/s11064-006-9271-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Accepted: 08/09/2006] [Indexed: 10/23/2022]
Abstract
Diurnal changes in Chordc1 mRNA were recently described in mouse hypothalamus. This report shows that Chordc1 mRNA changes rhythmically throughout the entire adult brain with highest expression levels occurring around the dark-light transition. The rhythmic cycling pattern of Chordc1 was retained under various light-dark schedules and analysis of adult whole brain revealed diurnal patterns that were different than young animals (postnatal day (P) 6). Analysis of adult hippocampus, prefrontal cortex and cerebellum confirmed these observations and a comparison between adult and P6 animals using in situ hybridization indicated that Chordc1 underwent coordinated but altered diurnal changes in mRNA abundance during development. Further, a developmental profile of Chordc1 expression beginning at embryonic day 17 revealed a regional distribution of Chordc1 consistent with its adult pattern. These results suggest that Chordc1 mRNA is under complex and widespread transcriptional regulation during development and implicate Chordc1 in circadian and/or homeostatic mechanisms in mammalian brain.
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Affiliation(s)
- Jason R Gerstner
- Neuroscience Training Program and Department of Psychiatry, University of Wisconsin-Madison, Madison, WI 53719, USA
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63
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Sládek M, Jindráková Z, Bendová Z, Sumová A. Postnatal ontogenesis of the circadian clock within the rat liver. Am J Physiol Regul Integr Comp Physiol 2006; 292:R1224-9. [PMID: 17095653 DOI: 10.1152/ajpregu.00184.2006] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In mammals, the circadian oscillator within the suprachiasmatic nuclei (SCN) entrains circadian clocks in numerous peripheral tissues. Central and peripheral clocks share a molecular core clock mechanism governing daily time measurement. In the rat SCN, the molecular clockwork develops gradually during postnatal ontogenesis. The aim of the present work was to elucidate when during ontogenesis the expression of clock genes in the rat liver starts to be rhythmic. Daily profiles of mRNA expression of clock genes Per1, Per2, Cry1, Clock, Rev-Erbalpha, and Bmal1 were analyzed in the liver of fetuses at embryonic day 20 (E20) or pups at postnatal age 2 (P2), P10, P20, P30, and in adults by real-time RT-PCR. At E20, only a high-amplitude rhythm in Rev-Erbalpha and a low-amplitude variation in Cry1 but no clear circadian rhythms in expression of other clock genes were detectable. At P2, a high-amplitude rhythm in Rev-Erbalpha and a low-amplitude variation in Bmal1 but no rhythms in expression of other genes were detected. At P10, significant rhythms only in Per1 and Rev-Erbalpha expression were present. At P20, clear circadian rhythms in the expression of Per1, Per2, Rev-Erbalpha, and Bmal1, but not yet of Cry1 and Clock, were detected. At P30, all clock genes were expressed rhythmically. The phase of the rhythms shifted between all studied developmental periods until the adult stage was achieved. The data indicate that the development of the molecular clockwork in the rat liver proceeds gradually and is roughly completed by 30 days after birth.
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Affiliation(s)
- Martin Sládek
- Institute of Physiology, Vídenská 1083, Prague 4, 142 20, Czech Republic
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64
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Weinert D, Waterhouse J. The circadian rhythm of core temperature: effects of physical activity and aging. Physiol Behav 2006; 90:246-56. [PMID: 17069866 DOI: 10.1016/j.physbeh.2006.09.003] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Accepted: 09/04/2006] [Indexed: 11/23/2022]
Abstract
The circadian rhythm of core temperature depends upon several interacting rhythms, of both endogenous and exogenous origin, but an understanding of the process requires these two components to be separated. Constant routines remove the exogenous (masking) component at source, but they are severely limited in their application. By contrast, several purification methods have successfully reduced the masking component of overt circadian rhythms measured in field circumstances. One important, but incidental, outcome from these methods is that they enable a quantitative estimate of masking effects to be obtained. It has been shown that these effects of activity upon the temperature rhythm show circadian rhythmicity, and more detailed investigations of this have aided our understanding of thermoregulation and the genesis of the circadian rhythm of core temperature itself. The observed circadian rhythm of body temperature varies with age; in comparison with adults, it is poorly developed in the neonate and deteriorates in the aged subject. Comparing masked and purified data enables the reasons for these differences--whether due to the body clock, the effector pathways or organs, or irregularities due to the individual's lifestyle--to begin to be understood. Such investigations stress the immaturity of the circadian rhythm in the human neonate and its deterioration in elderly compared with younger subjects, but they also indicate the robustness of the body clock itself into advanced age, at least in mice.
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Affiliation(s)
- Dietmar Weinert
- Institute of Zoology, Martin-Luther-University Halle-Wittenberg, D-06108 Halle, Germany.
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65
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Sumová A, Bendová Z, Sládek M, El-Hennamy R, Laurinová K, Jindráková Z, Illnerová H. Setting the biological time in central and peripheral clocks during ontogenesis. FEBS Lett 2006; 580:2836-42. [PMID: 16563387 DOI: 10.1016/j.febslet.2006.03.023] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 03/06/2006] [Indexed: 10/24/2022]
Abstract
In mammals, the principal circadian clock within the suprachiasmatic nucleus (SCN) entrains the phase of clocks in numerous peripheral tissues and controls the rhythmicity in various body functions. During ontogenesis, the molecular mechanism responsible for generating circadian rhythmicity develops gradually from the prenatal to the postnatal period. In the beginning, the maternal signals set the phase of the newly developing fetal and early postnatal clocks, whereas the external light-dark cycle starts to entrain the clocks only later. This minireview discusses the complexity of signaling pathways from mothers and the outside world to the fetal and newborn animals' circadian clocks.
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Affiliation(s)
- Alena Sumová
- Department of Neurohumoral Regulations, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
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