In the brain, aquaporin-1 (AQP-1), a water channel for high osmotic water permeability, is mainly expressed in the apical membrane of the ventricular choroid plexus and regulates for-

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...

In recent years, it has become increasingly evident that angiotensins synthesized in the brain contribute to regulating body fluid homeostasis. Although angiotensinogen, the unique angiotensin precursor, is produced in the brain, the factors that regulate its gene expression remain unknown. We recently found that TTF-1, a homeodomain-containing transcription factor essential for the development of the fetal diencephalon, is postnatally expressed in discrete areas of the hypothalamus. We now report that the subfornical organ, an important site of angiotensinogen synthesis, is an extrahypothalamic site of TTF-1 expression. Double in situ hybridization histochemistry demonstrated the presence of TTF-1 mRNA in angiotensinogen-producing cells of the rat subfornical organ. RNase protection assays showed that TTF-1 and angiotensinogen mRNA levels are simultaneously increased in the subfornical organ by water deprivation. The angiotensinogen promoter contains seven presumptive TTF-1 binding motifs, four of which are recognized by the TTF-1 homeodomain. In the C6 glioma cell line, TTF-1 transactivates the angiotensinogen promoter in a dose-dependent manner. This transactivation is abolished by deletion of the TTF-1 binding motif at ؊125. Intracranial administration of an antisense TTF-1 oligodeoxynucleotide decreased angiotensinogen mRNA in the subfornical organ and dramatically reduced the animal's water intake while increasing urine excretion. Moreover, plasma arginine vasopressin content was decreased by the same treatment. These results demonstrate a novel role for TTF-1 in the regulation of body fluid homeostasis, exerted via the transactivational control of angiotensinogen synthesis in the subfornical organ.The control of body fluid volume and blood pressure is a critical homeostatic process required for normalcy of the internal environment and for the preservation of life. Many studies have demonstrated that the renin-angiotensin system (RAS) 1 plays an important role in the regulation of fluid volume balance, blood pressure, and other related biological responses through the generation of angiotensin II (ANG II) (1). The existence of a brain RAS in addition to the peripheral RAS has also been established (2, 3). All components of the peripheral RAS have been found in the brain, most notably in the subfornical organ (SFO). The SFO is a circumventricular organ (CVO) of the lamina terminalis located at the top of the dorsal third ventricle (4). It is composed of fenestrated capillary loops in addition to glial cells, but in contrast to other CVOs such as the median eminence of the hypothalamus, it also contains neuronal cell bodies (1, 5). The SFO of rats contains high concentrations of angiotensinogen (AoGen) (6), the angiotensin precursor; renin-like activity (that converts AoGen to ANG I) (7); angiotensin-converting enzyme (which converts ANG I to ANG II) (8); the peptide ANG II (9); and AT 1 -type ANG II receptors (3). Thus, the SFO is not only a target for circulating ANG II, which exerts a potent dipsogenic ef...

We sought to identify genes affected by the aging process in the rat hippocampus using cDNA expression array analysis. RNA samples were extracted from the hippocampus of 2-month-old and 20-month-old rats and reverse-transcribed in the presence of [32P]dCTP. Membrane sets of Rat Atlas array 2 (Clontech) were hybridized with cDNA probe sets. Among a total of 1176 cDNAs, 23 showed significant (more than 2-fold) changes between groups. Eight genes were increased in the old group, while the remaining fifteen genes were decreased. Reverse transcription-polymerase chain reaction (RT-PCR) was used to validate the relative expression pattern obtained by the cDNA array. The results were consistent for 20 of the 23 genes tested. Most interesting findings were the decrease in expression of proteins for energy metabolism, proteins involved in secretion, and ribosomal proteins. The possible physiological significance of these changes are discussed.

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