The suprachiasmatic nucleus and the circadian time-keeping system revisited

Esseveldt, Lisette E van; Lehman, Michael N.; Boer, G.J.

doi:10.1016/s0165-0173(00)00025-4

Cited by 260 publications

(125 citation statements)

References 389 publications

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“…Circadian rhythms generated in the SCN, which secondarily regulate rhythms in other nuclei of hypothalamus, via the release of several factors, including arginine vasopressin and vasoactive intestinal peptide (38), may well generate the daily changes in PACAP expression in the hypothalamus. PACAP released from the SCN may also act as a rhythm regulator for hypothalamic cells outside the SCN, because PACAP and its receptor level show daily change outside SCN, as described above.…”

Section: Discussionmentioning

confidence: 99%

Regulation of Pituitary Adenylate Cyclase-activating Polypeptide Gene Transcription by TTF-1, a Homeodomain-containing Transcription Factor

Kim¹,

Hur²,

Son³

et al. 2002

Journal of Biological Chemistry

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Pituitary adenylate cyclase-activating polypeptide (PACAP) is an important hypophysiotrophic factor as well as a regulator for immune, reproductive, and neural tissues. We recently found that TTF-1, a homeodomain-containing transcription factor essential for the development of the fetal diencephalon, is postnatally expressed in the hypothalamic area and plays a transcription regulatory role for certain neurohormones. Based on the similarity of synthesis sites between PACAP and TTF-1 and, moreover, on the presence of conserved core TTF-1 binding motifs in the 5-flanking region of the PACAP gene, we sought to uncover a regulatory role of TTF-1 in PACAP gene transcription. The TTF-1 homeodomain binds to six of the seven putative binding domains observed in the 5-flanking region of the PACAP gene. In the C6 glioma cell-line, TTF-1 activates the PACAP promoter in a dose-dependent manner. This transactivation of PACAP by TTF-1 was totally removed when the core TTF-1 binding motif at ؊369 was deleted. RNase protection assays showed that TTF-1 and PACAP mRNAs have daily fluctuations in the rat hypothalamus. They both were at low levels during the day and high levels during the night. Intracerebroventricular administration of an antisense TTF-1 oligodeoxynucleotide significantly decreased the PACAP mRNA level as well as TTF-1 protein content in the rat hypothalamus, suggesting that TTF-1 also regulates PACAP transcription in vivo. Moreover, the TTF-1 promoter was inhibited by molecular oscillators of CLOCK and BMAL-1. Taken together, these data suggest that TTF-1 plays an important regulatory role in the gene transcription for PACAP, which may be important for the generation of a daily rhythm of hypothalamic PACAP gene expression.Pituitary adenylate cyclase-activating polypeptide (PACAP) 1 was originally isolated from the ovine hypothalamus (1, 2) and was classified as a member of the secretin-glucagon-vasoactive intestinal peptide family (1). PACAP plays the role of a hypophysiotropic factor and regulates the synthesis and secretion of pituitary hormones through the hypothalamo-hypophysial portal system (3). Although PACAP immunoreactivity is found in nearly all brain regions, its highest concentration is in the hypothalamus of both rat and human (3, 4). In the hypothalamus, PACAP immunoreactivity is primarily localized to the cells of the paraventricular and supraoptic nuclei (3, 4). PACAP is found both in neurons terminating on hypophysial blood vessels of the median eminence as well as in neurons projecting to the posterior pituitary. Therefore, PACAP may act not only as a hypophysiotropic factor regulating anterior pituitary hormone release but as a posterior pituitary hormone as well. It is also an important factor in the regulation of peripheral tissues such as ovary and testis and of the immune system.Recently, the 5Ј-flanking region of PACAP gene was characterized and shown to have several sequence motifs homologous to the cAMP response element (CRE), the TPA response element (TRE), and the growth hormone factor...

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Section: Discussionmentioning

confidence: 99%

Regulation of Pituitary Adenylate Cyclase-activating Polypeptide Gene Transcription by TTF-1, a Homeodomain-containing Transcription Factor

Kim¹,

Hur²,

Son³

et al. 2002

Journal of Biological Chemistry

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“…Daily rhythmicity is generated by a circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus, which is modulated by environmental cycles of light and darkness, food availability, ambient temperature, and other factors (Van Esseveldt et al, 2000;Helfrich-Förster, 2004). Circadian rhythmicity implies that under constant external condition (without time cues) the rhythms free-run with an endogenous period are close but not identical to 24 h. Several physiologic rhythms, including those of the cardiovascular system, react to both endogenous and exogenous influences (Guo and Stein, 2003).…”

Section: Introductionmentioning

confidence: 99%

Chronobiologic blood pressure assessment: Maturation of the daily rhythm in newborn foals

et al. 2008

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Circadian rhythmicity of physiological processes in animals has been described for some variables. In order to investigate the daily rhythmicity of blood pressure, seven foals (Equus caballus) were used for 40 days after birth. Measurements of blood pressure were done by means of an oscillometric apparatus (Argus TM-7, Schiller, Barr Switzerland) with the foals in a standing position and the cuff placed around the tail. Blood pressure was recorded twice a day, 1 hour before dawn and 1 hour before dusk for the first 10 days of life, every 2 days from the 11 th to the 32 nd day, on the 36 th and on the 40 th day. Two-way repeated measures analysis of variance (ANOVA) were used to determine statistically significant differences between the mean values recorded at dawn and dusk during the study. Analysis of variance showed a significant effect of time (p<0.0001), during the first 40 days of life. This study confirms a strong correlation between age and blood pressure in horse and the absence of blood pressure maturation in foals 40 days old. The results on the maturation of the daily rhythm of blood pressure in foals is a contribution to the study of the development of circadian rhythms in mammals. These results are also useful for the chronophysiological assessment of blood pressure in the horse.

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“…The relative contribution of these oscillators to the overall functioning of the circadian system at the whole-organism level varies among vertebrate species. In mammals, it is the hypothalamic oscillator that plays a major role in circadian organisation; it is located in a paired cell group in the hypothalamus, the suprachiasmatic nucleus (SCN) (van Esseveldt et al, 2000).…”

Section: Introductionmentioning

confidence: 99%