Androgen and Estrogen Receptors in Perinatal Ferret

Using DNA-cellulose affinity chromatography and either 3H-labeled dihydrotestosterone, testosterone, or estradiol, we qualitatively and quantitatively analyzed the androgenand estrogen-binding activities present in four regions of male and female ferret brain at prenatal, early and late neonatal, and adult ages. The cytosolic androgenand estrogen-binding activities in ferret brain at all ages studied were qualitatively similar in both sexes and in all brain regions and exhibited characteristics which resemble those of androgen and estrogen receptors from other species, including rodents and nonhuman primates. A developmental analysis indicated that high levels of both androgen and estrogen receptors were present in the hypothalamus-preoptic area as early as 5 days before birth. A significant, transient decline in concentrations of estrogen receptors (approximately &fold) occurred in anterior hypothalamus-preoptic area and mediobasal hypothalamus at 12 days of age in both males and females; this phenomenon has not been observed in any other species studied to date. The observed ontogeny of androgen receptors correlates with the known ability of testosterone, acting over postnatal days 5 to 20, to cause coital masculinization in ferrets, whereas the observed postnatal dip in estradiol receptor concentrations correlates with the inability of estradiol to cause coital masculinization or defeminization of receptive behavior in this species. Several aspects of brain sexual differentiation in ferrets are strikingly different from those in other species such as mice, rats, and hamsters. For example, a critical period of coital masculinization in ferrets occurs during the late neonatal period (Baum et al., 1982; Baum and Erskine, 1984), beginning approximately 5 days postnatally and extending to approximately 20 days after birth; in mice and rats, a critical period occurs perinatally with its onset being prenatal (see Vito and Fox, 1982), while in hamsters a critical period occurs during the early neonatal period (Eaton, 1970; Swanson, 1970), beginning at birth and ending 4 to 5 days later. Also unique to ferrets is the fact that coital masculinization occurs only after exposure to testosterone at late neonatal ages (Baum et al., 1982). Neonatal administration of either dihydrotestosterone or estradiol to female ferrets was ineffective. This is in contrast to mice, rats, and hamsters in which the aromatization of androgens to estrogen has been implicated in the process of coital masculinization (reviewed in Baum, 1979). Furthermore, in contrast to mice, rats, or hamsters, perinatal exposure of male or female 1 This work was supported by United States Public Health Service Grants HD 18660 (C. C. V.), HD 13634 and K02 MH 03392 (M. J. B.), and HD 18656 (T. 0. F.). We gratefully acknowledge the technical assistance of C. Gallagher and M. Kindy. ’ Present address: VENTREX Laboratories, Inc., 217 Read Street, Portland, ME 04103. 3 To whom correspondence should be addressed. 4 Present address: E. K. Shriver Center for Mental Retardation, 200 Trapelo Road, Waltham, MA 02254. ferrets to estrogen or androgen failed to reduce the animals’ capacity later to display receptive coital behavior in response to adult treatment with estradiol (i.e., perinatal steroids failed to cause receptive defeminization). Given these observations, we were interested in the possibility that these behavioral characteristics unique to ferrets may be correlated with speciesspecific differences in androgen and estrogen receptor systems in the brain, especially during the critical neonatal period of coital masculinization. In particular, we were interested in the ontogeny of androgen and estrogen receptors and their relationship to both the time course of coital masculinization and gonadal hormone production in male and female ferrets. In order to compare these developmental events in ferrets with similar events in other species, we chose to analyze receptors for both androgens and estrogens in developing and adult ferret brain (male and female) using methods which have proven to be sensitive in the analysis of receptors in mouse (Fox, 1975a, b; Vito and Fox, 1979; Vito et al., 1979), rat (Lieberburg et al., 1980; Vito and Fox, 1979, 1982; Wieland and Fox, 1981a), and hamster brain (Vito et al., 1983). The experiments described in this report (a) demonstrate the existence of typical androgen and estrogen receptors in adult ferret brain; (b) qualitatively characterize androgen and estrogen receptors in neonatal male and female ferret brain; and (c) quantitatively establish the relationship between age, sex, and receptor concentrations in four regions of ferret brain. Materials and Methods Animals. Pregnant ferrets were purchased from Marshall Research Farm (North Rose, NY), approximately 2 weeks before the expected