title: Exposure to dexamethasone during late gestation causes female-specific decreases in core body temperature and prepro-thyrotropin-releasing hormone expression in the paraventricular nucleus of the hypothalamus in rats.
abstract: Synthetic glucocorticoids (GC) have been used to promote lung development in preterm infants, thereby decreasing respiratory distress syndrome and mortality, yet, concern has arisen from reports that such treatment predisposes individuals to disease in adulthood. Given the variety of preclinical studies that show metabolic and behavioral abnormalities in adulthood following fetal exposure to synthetic GC, we examined the effect of in utero exposure to the synthetic GC, dexamethasone (DEX), on hypothalamic expression of thyrotropin-releasing hormone (TRH) a central neuropeptide involved in mediating behavior and metabolic balance. Pregnant Sprague-Dawley rats were administered 0.4mg/kg DEX on gestational days 18-21. As adults (postnatal day (PD) 60), the offspring were fitted with temperature sensing transmitters allowing real-time monitoring of core body temperature (CBT) across the 24h light dark period. This revealed a significant decrease in CBT throughout the day in prenatal DEX-treated females on estrus and diestrus, but not in male offspring. The reduction in CBT by prenatal DEX exposure was accompanied by a significant decrease in the expression of Trh transcript in the paraventricular nucleus of the hypothalamus (PVN) of female rats at PD 60 and this effect was also present on PD7. There was also a female-specific reduction in the number of preproTRH-immunoreactive (ir) neurons in the PVN, with ppTRH-ir nerve fibers decreases that were present in both male and female offspring. No changes in thyroid hormone (triiodothyronine, T3; thyroxine, T4) were observed in adult offspring, but during development, both males and females (PD14) had lower T3 and T4 levels. These data indicate abnormal expression of TRH results from fetal DEX exposure during late gestation, possibly explaining the decreased CBT observed in the female offspring.
authors.affiliation: University of Arizona College of Medicine-Phoenix, Department of Basic Medical Sciences, Phoenix, AZ 85004-2157, United States. carbone@email.arizona.edu
authors.forename: David L
authors.initials: DL
authors.lastname: Carbone
authors.forename: Damian G
authors.initials: DG
authors.lastname: Zuloaga
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Lacagnina
authors.forename: Robert F
authors.initials: RF
authors.lastname: McGivern
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Handa
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D000893:Anti-Inflammatory Agents / Q000009:adverse effects*; D001831:Body Temperature / Q000187:drug effects*; D002940:Circadian Rhythm / Q000187:drug effects; D003907:Dexamethasone / Q000009:adverse effects*; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D005865:Gestational Age; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects* / Q000378:metabolism; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012727:Sex Characteristics; D012737:Sex Factors; D013973:Thyrotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism*; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism
chemical_list: D000893:Anti-Inflammatory Agents; D011498:Protein Precursors; D012333:RNA, Messenger; D014284:Triiodothyronine; C063596:prepro-thyrotropin-releasing hormone; D013973:Thyrotropin-Releasing Hormone; D003907:Dexamethasone; D013974:Thyroxine