Sexual cycles in female dogs treated with androgen during development

Abstract

This experiment was conducted to study hormonal and behavioral cycles in female dogs exposed to androgen during development. The four groups, each consisting of five subjects, were "Normal" females, "Prenatal" females exposed to testosterone propionate (TP) before birth, "Postnatal" females injected with TP for 3 months postpartum, and "Prepost" females exposed to TP in utero and again to testosterone for 4--6 weeks after birth. All Normal females had two estrous cycles during which they showed vaginal bleeding, ovulation, progesterone (P) secretion, sexual receptivity, and were attractive to males. All androgen-treated females showed at least 1 cycle with ovulation and P secretion. Three Postnatal females developed the delayed anovulatory syndrome. Genital bleeding through the vagina (Postnatal group), or through the "penis" (Prenatal and Prepost groups), occurred in 4 Postnatal, 3 Prenatal, and 1 Prepost female. Attractiveness for males was observed in all Prenatal and Postnatal females, but in no Prepost subject. Receptivity was present in four of five Prenatal females but not in any Postnatal or Prepost female. Occurrence of cycles in treated females indicated functional integrity and sensitivity to estrogen in brain mechanisms producing gonadotropin-releasing hormones. Absence of receptivity is referred to diminished responsiveness to ovarian hormones in brain mechanisms mediating receptive behavior. Absence of genital bleeding and lack of attractivity are due to lowered response to estrogen in uterine and vaginal epithelium which results in reduced extravasation of blood, and in failure to secrete the putative "pheromonal" agent normally responsible for attractiveness.