Jl. Zehr et al., ESTRADIOL INCREASES FEMALE SEXUAL INITIATION INDEPENDENT OF MALE RESPONSIVENESS IN RHESUS-MONKEYS, Hormones and behavior (Print), 33(2), 1998, pp. 95-103
Copulation and female initiation of sexual behavior vary across the ov
arian cycle, suggesting that female hormonal condition influences fema
le sexual motivation in rhesus monkeys. However, the effects of hormon
es on female sexual motivation are difficult to identify because male
behavior also varies with female hormonal condition. During the nonbre
eding season, male rhesus monkeys are sexually unresponsive to females
; thus the effects of estradiol treatment on female sexual motivation
can be examined independent of male behavior. This study administered
estradiol to five ovariectomized females living in a large age-graded
social group during the nonbreeding season. The behavior of these fema
les with and without estradiol treatment was compared. Data were colle
cted concurrently on five intact, noncycling, nonpregnant females. Est
radiol treatment significantly increased sexual initiation by ovariect
omized females toward males without any significant changes in male be
havior. Estradiol-treated females also displayed greater sexual initia
tion than nonpregnant, intact females. Both estrogen and progesterone
were important predictors of sexual initiation in females, with proges
terone having an inhibitory effect. Endogenous progesterone levels in
females were negatively correlated with male contact behavior, suggest
ing that female attractiveness is reduced by progesterone. This study
provides further support for estrogen as the critical steroid increasi
ng female sexual motivation in primates. (C) 1998 Academic Press.