Neuronal TRH synthesis: Developmental and circadian TRH mRNA levels

Dexamethasone represses cAMP rapid upregulation of TRH gene transcription: identification of a composite glucocorticoid response element and a cAMP response element in TRH promoter

“…TRH gene expression in the PVN is strictly controlled by the feedback action of thyroid hormones (Koller et al 1987, Segerson et al 1987b, Rondel et al 1988, Hollenberg et al 1995, Satoh et al 1999 and is regulated in multiple physiological conditions including: circadian and estrous cycles (Covarrubias et al 1988, Uribe et al 1991, suckling and weaning (Uribe et al 1993, 1995b, Sánchez et al 2001, cold stress (Zoeller et al 1990, Uribe et al 1993, Sánchez et al 2001 and fasting (Blake et al 1991, Legradi et al 1997a, Fekete et al 2002. In addition, a fast and transient increase in proTRH mRNA levels in the PVN (maximal at 30-60 min) is produced by cold exposure or suckling (Uribe et al 1993, Sánchez et al 2001, conditions that activate TRH release from the median eminence (Arancibia et al 1983, de Greef et al 1987, Rondel et al 1988.…”

Distribution, Cellular Localization, and Ontogeny of Preprothyrotropin-Releasing Hormone-(160–169) (Ps4)-Binding Sites in the Rat Pituitary1

“…Previous studies have shown that TRH receptors are also expressed at birth and that their density increases postnatally (41,42). Concurrently, the number of TRH-producing neurons in the paraventricular nucleus increases during the first week of life (43,44). However, in rats, the capillary loops of the portal blood system penetrate the median eminence only at the end of the first postnatal week (45), and TRHcontaining nerve endings make contact with the portal blood vessels only 2 days after birth (46).…”

Some Events of Thyrotropin-Releasing Hormone Metabolism Are Regulated in Lactating and Cycling Rats

“…We previously noted a coordinated regulation of TRH mRNA levels in the hypothalamus during the circadian cycle [18]. Levels of hypothalamic TRH mRNA during the estrous cycle cannot be compared with TRH levels because they are the mean fluctutions from various nuclei.…”

“…Following electrophoresis, gels were stained with ethidium bromide (4 ug/m l) for 5 min, destained for 6-8 h with water, and photographed with ultravio let transillumination for RNA quantification. Loaded samples were transferred to a nitrocellulose membrane for 24-36 h using 20 x SSC; the membranes were then baked for 2 It at 80 "C. Hybridizations were performed as described [18] using the rat cDNA as probe [19]. Ribosomal RNA (stained with ethidium bromide) and TRH mRNA auto radiographic bands were quantified by laser densitometry (Biomed Instruments, Fullerton, Calif.. USA).…”

“…Cytoplasmic RNA was extracted as previously described [18]. Each hypothalamus was homogenized in 200 pi of 50 m.V/ Tris-HCI, pH 7.4, 25 mM NaCI, 5m M MgCI; 8 pi of 25% Triton X -100 and 100 ul of 72% sucrose were added, and the homogenate was centrifuged for 10 min at 4 °C; the supernatant (cytosolic fraction) where 100 pi of 6% sodium dodecyl sulfate, 0.4 M NaCI and 40 mM ethylenediamineteiraacetic acid solution were added, was extracted 3 times with phenol-chloro form (voi/vol); to the aqueous phase, 5 M NaCI (1 /25th o f total vol ume) and 2 vol o f ethanol were added and left at -7 0 °C for 12 h to precipitate total RNA.…”