Divergent roles for estrogens and androgens in the expression of female goat sexual behavior D. Bradley Imwalle and Larry S. Katz * Animal Sciences, Cook College, Rutgers University, New Brunswick, NJ 08901-8525, USA Received 19 August 2003; revised 23 January 2004; accepted 26 January 2004 Available online 27 April 2004 Abstract We tested the hypothesis that the activation of the androgen receptor (AR) is required for full expression of female goat sexual behavior. Once a week for 6 weeks, ovariectomized (OVX) females were given priming doses of progesterone 72 and 48 h before behavioral observation. Estradiol (E 2 ; 100 Ag), testosterone (T; 100 mg), or sesame oil was supplied 14 h before behavioral testing. Six goats received the AR antagonist flutamide (9 mg/kg sc) 8 h before and 4 h after steroid injection. Six goats received the carrier only. After 3 weeks, flutamide and carrier treatments were switched so that all females received all treatments. Treatments with E 2 and T were equally effective in eliciting estrus-typical behaviors (sniffing, courting, leg kicks, mount attempts by males, bouts of thrusting by males, ejaculations, and flehman responses) compared to treatment with oil. Flutamide treatment enhanced proceptive behaviors in E 2 -treated females compared to other treatment groups; this was most likely via enhanced tail wagging. Moreover, compared to goats given T + carrier, T + flutamide significantly reduced receptivity in females. The results of this experiment implicate the AR as an important facilitator of some aspects of the female goat sexual behavior. However, the results of this experiment do not show whether androgens influence estrous behaviors alone or in some combination with estrogen. D 2004 Elsevier Inc. All rights reserved. Keywords: Flutamide; Proceptivity; Tail wagging; Receptivity; Libido In most ovariectomized (OVX) female mammals that are spontaneous ovulators, induction of estrus is accomplished by sequential administration of estradiol (E 2 ) or progester- one (P 4 ) in some combination. For example, although E 2 alone elicits some components of estrus in OVX female rodents, only E 2 plus P 4 (24–48 h after E 2 ) allows for the full complement of female sexual behavior (Auger, 2001). However, estrus in OVX goats may be induced by E 2 alone or, outside the breeding season, by P 4 treatment before E 2 administration (Billings and Katz, 1997). In addition to estrogens, androgens may be important modulators of female sexual behavior (see review by Do ¨rner, 1976) either directly or following aromatization to estrogen. Work done using sheep and goats supports the notion that the androgen receptor (AR) may play a facilita- tive role in female sexual behavior. In the ovary-intact goat, both estrogens and androgens are produced concomitant with the regression of the corpus luteum (Homeida and Cooke, 1984). Plasma testosterone (T) and E 2 concentra- tions continue to increase in the female, and when a threshold level is reached, estrus is observed. In sheep, the antiandrogen cyproterone acetate in conjunction with T administration blocked receptivity; however, this work is controversial as cyproterone acetate also functions as a progestin (Fabre-Nys and Signoret, 1980). Preliminary data in our laboratory suggested that the aromatizable androgens T and androstenedione (A 4 ) induce the expression of female goat sexual behavior (Lindia and Katz, 2000). These researchers attempted to induce estrus in OVX goats using E 2 , T, A 4 , or DHT. They found that E 2 ,A 4 , and T all increased expression of estrous behavior. However, T and A 4 tended to elicit higher attractivity and receptivity scores than E 2 treatment. Dihydrotestosterone alone had no effect on sexual behavior. Increased doses of E 2 did not enhance behavioral responses. Taken together, these obser- 0018-506X/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.yhbeh.2004.01.008 * Corresponding author. Department of Animal Sciences, Rutgers, The State University of New Jersey, 106 Bartlett Hall, 84 Lipman Drive, New Brunswick, NJ 08901-8525. Fax: +1-732-932-6996. E-mail address: katz@aesop.rutgers.edu (L.S. Katz). www.elsevier.com/locate/yhbeh Hormones and Behavior 46 (2004) 54 – 58