Please cite this article in press as: Souza, A., et al., Neonatal hypoxic–ischemic encephalopathy reduces c-Fos activation in the rat hippocampus: evidence of a long-lasting effect. Int. J. Dev. Neurosci. (2014), http://dx.doi.org/10.1016/j.ijdevneu.2014.09.003 ARTICLE IN PRESS G Model DN 1925 1–10 Int. J. Devl Neuroscience xxx (2014) xxx–xxx Contents lists available at ScienceDirect International Journal of Developmental Neuroscience j ourna l ho me page: www.elsevier.com/locate/ijdevneu Neonatal hypoxic–ischemic encephalopathy reduces c-Fos activation in the rat hippocampus: evidence of a long-lasting effect Andressa Souza a,c,d,f , Jairo Alberto Dussan-Sarria a , Liciane Fernandes Medeiros b,c,d , Q1 Ana Cláudia Souza a,c,d , Carla Oliveira a,c,d , Vanessa Leal Scarabelot b,c,d , Lauren Naomi Adachi a,c,d , Elisa Cristiana Winkelmann-Duarte e , Bárbara Beatriz Philippi-Martins e , Carlos Alexandre Netto c , Wolnei Caumo a , Iraci L.S. Torres a,b,c,d,∗ a Graduate Program in Medicine: Medical Sciences, Universidade Federal do Rio Grande do Sul, 90035-003, Porto Alegre, Brazil b Graduate Program in Biological Sciences: Physiology, Universidade Federal do Rio Grande do Sul, 90035-003, Porto Alegre, Brazil c Pain Pharmacology and Animal Models of Neuromodulation Laboratory, Department of Pharmacology, Institute of Basic Health Sciences, Universidade Federal do Rio Grande do Sul, 90050-170, Porto Alegre, Brazil d Animal Experimentation Unit, Hospital de Clínicas de Porto Alegre Graduate Research Group, 90035-003, Porto Alegre, Brazil e Department of Morphological Sciences, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Brazil f Graduate Program in Health and Human Development, Centro Universitário Unilasalle, 92010-000, Canoas, Brazil a r t i c l e i n f o Article history: Received 22 June 2014 Received in revised form 13 September 2014 Accepted 16 September 2014 Keywords: Neonatal hypoxia–ischemia encephalopathy Nociceptive behavior c-Fos protein BDNF TNF- a b s t r a c t The effect of neonatal hypoxic–ischemic encephalopathy (HIE) on maturation of nociceptive pathways has been sparsely explored. To investigate whether neonatal HIE alters neuronal activity, nociceptive behavior, and serum neuroplasticity mediators (brain-derived neurotrophic factor [BDNF] and tumor necrosis factor- [TNF]) in the short, medium, and long term. Neonate male Wistar rats were randomized to receive a brain insult that could be either ischemic (left carotid artery ligation [LCAL]), hypoxic (8% oxygen chamber), hypoxic–ischemic (LCAL and hypoxic chamber), sham-ischemic, or sham-hypoxic. Neuronal activity (c-Fos activation at region CA1 and dentate gyrus of the hippocampus), nociceptive behavior (von Frey, tail-flick, and hot-plate tests), neuroplasticity mediators (BDNF, TNF), and a cellular injury marker (lactase dehydrogenase [LDH]) were assessed in blood serum 14, 30, and 60 days after birth. Neonatal HIE persistently reduced c-Fos activation in the ipsilateral hippocampal region CA1; however, contralateral c-Fos reduction appeared only 7 weeks after the event. Neonatal HIE acutely reduced the paw withdrawal threshold (von Frey test), but this returned to normal by the 30th postnatal day. Hypoxia reduced serum LDH levels. Serum neuroplasticity mediators increased with age, and neonatal HIE did not affect their ontogeny. Neonatal HIE-induced reduction in neuronal activity occurs acutely in the ipsilateral hippocampal region CA1 and persists for at least 60 days, but the contralateral effect of the insult is delayed. Alterations in the nociceptive response are acute and self-limited. Serum neuroplasticity mediators increase with age, and remain unaffected by HIE. © 2014 Published by Elsevier Ltd. on behalf of ISDN. 1. Introduction The development of the nociceptive system in humans occurs during the second and third gestational trimesters, and continues during the first 2 years of life (Anand and Hickey, 1987). Nociceptive Q2 ∗ Corresponding author at: Departamento de Farmacologia – ICBS, UFRGS. Rua Sarmento Leite, 500 sala 202. 90050-170, Porto Alegre, RS, Brazil. Tel.: +55 51 3316 3183; fax: +55 51 3316 3121. E-mail address: iracitorres@gmail.com (I.L.S. Torres). afferents are myelinated in the 30th gestational week (Kostovic and Rakic, 1990), thalamocortical fibers in the 37th (Deshpande and Anand, 1996), and inhibitory pathways during the 3rd postnatal week (Boucher et al., 1998; Van Praag and Frenk, 1991). Although the maturation of the nociceptive system in rats occurs in an order similar to that seen in humans, a newborn rat has a nociceptive system that resembles that of a human fetus at 24 gestational weeks (Dobbing and Sands, 1979; Andrews and Fitzgerald, 1997; Marsh et al., 1997), while that of a 7-day-old rat pup (P7) corresponds to that of a full-term human neonate (Tuor et al., 1996). Thus, any insult to the central nervous system (CNS) occurring in this period http://dx.doi.org/10.1016/j.ijdevneu.2014.09.003 0736-5748/© 2014 Published by Elsevier Ltd. on behalf of ISDN. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46