Endocrine Control of Behavioural Sexual Differentiation in the Male Ferret

Abstract

Over the past 25 years much evidence has accumulated (reviewed in Baum 1979) to show that sexual dimorphisms in mammalian social behaviour ultimately derive from dimorphic patterns of sex steroid hormone secretion and brain action during critical perinatal periods of development. It is well established that a primary source (in the view of many investigators, the only source) of this perinatal sex difference in steroidal environment results from the presence of testes in the male. Over the past 13 years we have explored the contribution of testicular secretions to the process of brain and behavioural sexual differentiation in the male ferret (Mustek furo), a carnivorous mammal in which gestation lasts approx. 42 days. The results of an initial experiment (Baum 1976) showed that prenatal administration of testosterone propionate (TP) to female ferrets caused extensive masculinization of the external genital organs, whereas this treatment had no effect on the females’ ability to display either feminine or masculine coital behaviour in adulthood, following gonadectomy and concurrent treatment with either oestradiol benzoate (OB) or TP. By contrast, females which received TP over the first 10 postnatal days of life later displayed high levels of masculine coital behaviour, when tested with concurrent OB or TP stimulation. These findings focussed our attention on the late gestational and early postnatal ages of development as potentially important periods for the process of brain sexual differentiation in ferrets.