BEHAVIOURAL BRAIN RESEARCH ELSEVIER BehavIOural Brain Research 85 (1997) 143-159 Research Report Copulation activates Fos-like immunoreactivity in the male quail forebrain Simone L. Meddle a.\ Verdun M. King a, Brian K. Follett a.2, John C. Wingfield b, Marilyn Ramenofsky b, Agnes Foidart c, Jacques Balthazart c.* a BBSRC Group on Photoperiodism and Reproduction. School of Biological Sciences, University of Bristol, Bristol BS8 1 UG, UK b Department of Zoology. University of Washington, Seattle, WA 98105, USA C Laboratory of Biochemistry, University of Liege, 17 place Delcour (Bat. L1). Liege B-4020. Belgium Received 26 April 1996; received in revised form 26 August 1996; accepted 26 August 1996 Abstract It has been demonstrated using Fos immunocytochemistry that copulation activates specific cell populations in the mammalian brain. Prior to this study. no similar work has been carried out in birds. In mammals, Fos has identified brain circuits activated by genital (penile)/somatosensory and by olfactory/vomeronasal stimuli. Such inputs, of course, should play little or no role in birds (no penis. little or no role for olfaction) and a differential responsiveness could therefore be expected. Male Japanese quail (Coturnix japonica) were allowed to interact freely with adult females and the presence of active sexual behavior, including cloacal contact movements, was confirmed in each case. Control subjects were exposed to a domestic chick (same size as an adult quail) and no sexual behavior was observed. Copulation induced the appearance of Fos-like immunoreactive (FLI) cells in the preoptic area, the hyperstriatum ventrale, parts of the archistriatum. and the nucleus intercollicularis. Induction of FLI cells was observed throughout the rostral to caudal extent of the preoptic region of males from the level of the tractus septomesencephalicus to the level of the anterior commissure, and in the rostral part of the hypothalamus to the level of the supraoptic decussation. The FLI cells did not lie directly adjacent to the third ventricle, but were located 500-1000 11m from the ventricle wall at the level of the lateral edge of the medial preoptic nucleus or, in more caudal sections, in a position ventrolateral to the bed nucleus striae terminalis. It is unlikely that the Fos induction in males resulted from copulation-induced endocrine changes because copulation did not affect plasma levels of luteinizing hormone or testosterone. It is concluded that the responses were due to copulation- associated somatosensory inputs and/or to stimuli originating from the female. Keywords Sexual behavior: Neuronal activation, Preoptic area: Nucleus intercolhculans: Coturnix japonica: Immediate early gene 1. Introduction The anterior hypothalamic preoptic area (POA) plays a major role in the control of many aspects of repro- duction including male sexual behavior and control of gonadotrophin release in birds, as in mammals (reviews: in [7,49,52]). The association of the POA with sexual behavior was established through various studies includ- ing hormone implantation into discrete brain nuclei, * Corresponding author Fax: (32) (43) 665971: E-mail: jbalthazart@ulg ac be lPresent address: Department of PhYSIOlogy. Umversity of Edmburgh Medical School, Edmburgh EH8 9AG. UK 2Present address: UniverSity of Warwick, Coventry CV4 7AL UK. 0166-4328/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved PII SOI66-4328(96)00169-6 lesions, electrical stimulation, and analysis of hormone binding sites (reviews: [5,10,25,49,52,55]), In Japanese quail (Colurnix japonica) , a sexually dimorphic nucleus has been identified in the POA: the medial preoptic nucleus (POM) is significantly larger in males than in females [56,77], Behavioral studies have shown that the POM is a necessary and sufficient site for testosterone to act so as to activate male copulation. Lesions of this nucleus block the activation of the behavior by testoster- one while stereotaxic implantation of testosterone in the POM of castrated males restores full levels of behavioral activity [16,17]. Testosterone must also be aromatized within the POM to activate the behavior: implantation of aromatase inhibitors in the POA block the behavioral effects of the steroid only if they are implanted within