Contents lists available at ScienceDirect Hormones and Behavior journal homepage: www.elsevier.com/locate/yhbeh Prenatal thyroxine treatment promotes anxiolysis in male Swiss mice offspring Roberto Laureano-Melo a, ⁎ , Janaina Sena de Souza b , Rodrigo Rodrigues da Conceição b , Josie Marcelle Lira Albuquerque c , Nayana Coutinho Rodrigues a , Bruno Guimarães Marinho a , Emerson Lopes Olivares a , Gisele Giannocco b , Wellington da Silva Côrtes a a Multicenter Graduate Program in Physiological Sciences, Department of Physiological Sciences, Institute of Biological and Health Sciences, Federal Rural University of Rio de Janeiro, Seropédica, Brazil b Molecular and Translational Endocrinology Laboratory, Department of Medicine, Federal University of São Paulo, São Paulo, SP, Brazil c Federal Fuminense University, Niterói, RJ, Brazil ARTICLE INFO Keywords: Thyroxine Pregnancy Offspring Anxiety Serotonergic system GABAergic system ABSTRACT The proper functioning of the maternal thyroid plays a crucial role in fetal development. Thus, the aim of our study was to verify how maternal hyperthyroidism is able to change behavioral parameters in mice offspring during adulthood. For this purpose, pregnant Swiss mice (n = 24 and ~35 g) were randomly assigned into two groups: a control and a thyroxine (T4)-treatment group. The control was treated with 0.9% saline, while the treatment group received T4 (200 μg/kg, s.c.) once daily during the entire pregnancy period. After completing 70 days of life, a part of male offspring underwent a battery of tests, including open field, dark-light box, ele- vated plus maze, marble burying, rotarod and tail suspension tests. The other male pups were euthanized, being hippocampus and serum collected for RNA analysis and hormones measurement, respectively. Statistical analysis was performed using Student's t-test, and the means were considered significantly different when p < 0.05. In adult offspring, a significant decrease was observed for serum T3 in treated group. It was demonstrated that the T4 group had an increase in total distance traveled in an open field test. In the elevated plus maze test, we observed a higher time in opened arms as well as an increased in percentage of entries in these arms. In the hippocampus, T4 offspring had a higher expression of tryptophan hydroxylase 2 (TPH2), serotonin transporter (SERT) and glutamate decarboxylase 67 (GAD 67) in comparison to controls. These findings suggest that pre- natal T4 treatment alters hippocampal serotonergic and GABAergic systems, promoting anxiolysis in male adult offspring. 1. Introduction The prevalence of some diseases in adulthood presents a significant correlation with homeostatic disturbances during the fetal stage (Barker, 1990). This process is known as fetal programming (Godfrey and Barker, 2001). One of the main physiological factors that can affect the ontogeny of different physiological systems is maternal endocrine function (Fowden and Forhead, 2009). Therefore, the proper func- tioning of the maternal thyroid plays a crucial role in fetal development (Stricker et al., 2007). To reinforce this fact, thyroid function in humans is established only from the 16th week of pregnancy (Obregon et al., 2007). Until this period, the maternal thyroid is the major source of thyroid hormones (THs) to the fetus, being responsible for approximately 30% fetal bioavailability of these hormones (Calvo et al., 2002). The prevalence of overt hyperthyroidism ranges from 0.2% to 1.3% in iodine-sufficient parts of the world (Madariaga et al., 2014). A 20- year follow-up of the Whickham cohort reported an incidence of 80 cases/100,000 women/year (Vanderpump et al., 1995; Hollowell et al., 2002). A meta-analysis of European studies showed a mean prevalence of 0.75% and an incidence of 51 cases/100,000 women/year (Madariaga et al., 2014). In the United States, the National Health and Nutrition Examination Survey reported overt hyperthyroidism in 0.5% of the population while 0.7% had subclinical hyperthyroidism (Hollowell et al., 2002) with an overall prevalence of 1.3%. Studies from many other countries have all reported comparable incidence and https://doi.org/10.1016/j.yhbeh.2018.12.008 Received 18 June 2018; Received in revised form 12 December 2018; Accepted 16 December 2018 ⁎ Corresponding author at: Departamento de Ciências Fisiológicas, Instituto de Biologia, Universidade Federal Rural do Rio de Janeiro, BR 465, Km 7, 23897-000 Seropédica, RJ, Brazil. E-mail addresses: laureanomelor@gmail.com, laureanomelor@ufrrj.br (R. Laureano-Melo). Hormones and Behavior 108 (2019) 10–19 0018-506X/ © 2018 Elsevier Inc. All rights reserved. T