TitleThe volume of a sexually dimorphic nucleus in the ovine medial preoptic area/anterior hypothalamus varies with sexual partner preference.
Publication TypeJournal Article
Year of Publication2004
AuthorsRoselli, CE, Larkin, K, Resko, JA, Stellflug, JN, Stormshak, F
Date Published2004 Feb
KeywordsAnimals, Aromatase, Female, Gene Expression, Hypothalamus, Anterior, Male, Preoptic Area, RNA, Messenger, Sex Characteristics, Sexual Behavior, Animal, Sheep, Testosterone

Sheep are one of the few animal models in which natural variations in male sexual preferences have been studied experimentally. Approximately 8% of rams exhibit sexual preferences for male partners (male-oriented rams) in contrast to most rams, which prefer female partners (female-oriented rams). We identified a cell group within the medial preoptic area/anterior hypothalamus of age-matched adult sheep that was significantly larger in adult rams than in ewes. This cell group was labeled the ovine sexually dimorphic nucleus (oSDN). In addition to a sex difference, we found that the volume of the oSDN was two times greater in female-oriented rams than in male-oriented rams. The dense cluster of neurons that comprise the oSDN express cytochrome P450 aromatase. Aromatase mRNA levels in the oSDN were significantly greater in female-oriented rams than in ewes, whereas male-oriented rams exhibited intermediate levels of expression. Because the medial preoptic area/anterior hypothalamus is known to control the expression of male sexual behaviors, these results suggest that naturally occurring variations in sexual partner preferences may be related to differences in brain anatomy and capacity for estrogen synthesis.

Alternate JournalEndocrinology
PubMed ID14525915
Grant ListR01 RR 14270 / RR / NCRR NIH HHS / United States