The proposed research seeks to understand the neuroendocrine mechanisms that differentially control mate recognition and other aspects of psychosexual function in the two sexes of a carnivore, the ferret. Male and female ferrets rely on conspecifics' body odors to identify opposite-sex mating partners. The central hypothesis to be tested is that heterosexual mate recognition and sex partner preference depend on a comparison by sexually differentiated groups of hypothalamic neurons of these olfactory inputs, which are detected by receptors in the main olfactory epithelium and initially processed in the main olfactory bulb (MOB). An initial study will map the spatial distribution of c-fos glomerular activation in the MOB of gonadectomized male and female ferrets treated with estradiol or no sex steroid and exposed to male versus female anal scent gland odorants as well as a non-social odorant, L-menthone. Additional studies will determine (a) whether noradrenergic neurons of the locus coeruleus that specifically innervate those MOB glomeruli which respond to body odorants express estrogen receptors, and (b) whether immunotoxic lesioning of this subset of centrifugal, noradrenergic inputs to the MOB glomeruli disrupt the ability of estradiol to augment ferrets' ability to detect or show a preference to approach opposite-sex male scent gland odorants. Another study will explore the effects of excitotoxic lesions of the steroid-sensitive ventrolateral portion of the ventromedial hypothalamic nucleus on the preference of female ferrets to seek out opposite-sex body odors in Y-maze tests. A final study will determine whether bilateral occlusion of the vomeronasal duct, either alone or in combination with bilateral nares occlusion, will disrupt the capacity of either male or female ferrets to detect or show a preference to approach heterosexual odors or will reduce the display of scent marking and mating behaviors. Understanding sex differences in the neuroendocrine mechanisms controlling mate recognition in a higher mammal like the ferret could provide new insights into similar sexually dimorphic brain-behavior relationships in man.