Sex differences in the analgesic effects of ICI 182,780 and Flutamide on ureteral calculosis in rats Giannapia Affaitati a , Ilaria Ceccarelli b , Paolo Fiorenzani b , Cosmo Rossi a , Maria Caterina Pace c , Maria Beatrice Passavanti c , Caterina Aurilio c , Giuseppina Sorda d , Barbara Danielli d , Maria Adele Giamberardino a , Anna Maria Aloisi b, ⁎ a Pathophysiology of Pain Laboratory, Ce.S.I., “G. D'Annunzio” Foundation, University of Chieti, via Colle dell'Ara, 66013 Chieti Scalo (Chieti), Italy b Stress and Pain Neurophysiology Laboratory, Neuroscience and Applied Physiology Section, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy c Department of Anesthesiology, Surgical and Emergency Science, Second University of Napoli, Piazza Miraglia, 5, 80138 Napoli, Italy d San Carlo Clinic, Via Ospedale, 21, 20037 Paderno Dugnano (Milano), Italy abstract article info Article history: Received 11 May 2010 Revised 14 September 2010 Accepted 26 September 2010 Available online 1 October 2010 Keywords: Visceral pain Sex hormones Receptor antagonists To better define the involvement of gonadal hormones in the sex differences observed in experimental visceral pain, we administered antagonists of estrogen receptors (ICI 182,780 [ICI]) or androgen receptors (Flutamide [FLU]) to adult male and female rats suffering from artificial ureteral calculosis. Subjects were divided into groups and treated with one of the substances (ICI, FLU) or sweet almond oil (OIL, vehicle) for 5 days, starting 2 days before surgery. On day 3, animals underwent surgery, with half receiving an artificial calculosis (Stone) and half only a sham procedure. The animals' behavior (number and duration of ureteral crises) and blood hormone levels (estradiol and testosterone) were determined in all groups. In OIL-treated rats the number and duration of crises were higher in females than in males. The administration of ICI or FLU resulted in hormonal effects in males and behavioral effects in females. In males ICI treatment increased estradiol plasma levels and FLU increased testosterone plasma levels; in females ICI and FLU treatments both decreased the number and duration of the ureteral crises. These results, confirming previous findings of higher sensitivity of females than males to urinary tract pain, showed the modulatory effects of estrogen and androgen antagonists on the behavioral responses induced by pain but only in females. © 2010 Elsevier Inc. All rights reserved. Introduction The acknowledged presence of sex differences in pain has focused attention on steroid hormones (estrogens, androgens) which have been well investigated in several aspects of sexual dimorphism. Estrogens and androgens have been found to affect pain responses in humans as well as in experimental animals, although the results were sometimes contra- dictory due to sex, hormone concentration and the pain model used (Aloisi and Bonifazi, 2006; Clairborne et al., 2006; Craft et al., 2004; Kuba et al., 2006). The presence of higher pain in female subjects has focused attention on the role played by estrogens in pain mechanisms and several studies have confirmed their role in enhancing pain and hyperalgesia (Aloisi and Ceccarelli, 2000; Craft, 2007; Fehrenbacher et al., 2009); on the other hand estrogens have also been found to play an analgesic role, with particular reference to visceral pain, as demonstrated by several studies in which physiological changes, ovariectomy and estrogen receptor (ER) antagonists induced visceral hyperalgesia (Bradshaw and Berkley, 2002; Chaban and Micevych, 2005; Gaumond et al., 2002; Giamberardino et al., 2007). We recently showed, using a model of artificial calculosis in rats, that prolonged administration of estradiol in intact animals, to obtain supraphysiological concentrations of the hormone in both sexes, had a clear analgesic role but only in females (Aloisi et al., 2010). Estrogens and androgens, although considered female and male sexual hormones respectively, are present in both sexes at detectable levels and have profound effects on the subject's physiology (differentiation, development, maintenance of homeostasis). These hormones act on their cell targets through specific receptors able to rapidly change the excitability of neurons or slowly change cell metabolism. Estrogens act on estrogen receptors (ERs) α and β, known to be affected by age, sex and 17β-estradiol administration (see Micevych and Mermelstein, 2008; Tetel et al., 2009 for review). More recently a G-protein-coupled estrogen receptor (GPR30) was considered as a mediator of estrogenic activity (i.e. Kuhn et al., 2008; Levin, 2009). All functions mediated by these receptors can be blocked by ICI 182,780 (ICI), a steroidal estrogen receptor antagonist (Howell et al., 2000; Maggiolini and Picard, 2010). Hormones and Behavior 59 (2011) 9–13 ⁎ Corresponding author. Department of Physiology, Neuroscience and Applied Physiology Section, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy. Fax: + 39 0577 234037. E-mail address: aloisi@unisi.it (A.M. Aloisi). URL: http://www.unisi.it/ricerca/dip/fisiologia/fisiologia.html (A.M. Aloisi). 0018-506X/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.yhbeh.2010.09.008 Contents lists available at ScienceDirect Hormones and Behavior journal homepage: www.elsevier.com/locate/yhbeh