The ovine sexually dimorphic nucleus, aromatase, and sexual partner preferences in sheep

C. E. Roselli, F. Stormshak

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

We are using the domestic ram as an experimental model to examine the role of aromatase in the development of sexual partner preferences. This interest has arisen because of the observation that as many as 8% of domestic rams are sexually attracted to other rams (male-oriented) in contrast to the majority of rams that are attracted to estrous ewes (female-oriented). Our findings demonstrate that aromatase expression is enriched in a cluster of neurons in the medial preoptic nucleus called the ovine sexually dimorphic nucleus (oSDN). The size of the oSDN is associated with a ram's sexual partner preference, such that the nucleus is 2-3 times larger in rams that are attracted to females (female-oriented) than in rams that are attracted to other rams (male-oriented). Moreover, the volume of the oSDN in maleoriented rams is similar to the volume in ewes. These volume differences are not influenced by adult concentrations of serum testosterone. Instead, we found that the oSDN is already present in late gestation lamb fetuses (∼day 135 of gestation) when it is ∼2-fold greater in males than in females. Exposure of genetic female fetuses to exogenous testosterone during the critical period for sexual differentiation masculinizes oSDN volume and aromatase expression when examined subsequently on day 135. The demonstration that the oSDN is organized prenatally by testosterone exposure suggests that the brain of the male-oriented ram may be under-androgenized during development.

Original languageEnglish (US)
Pages (from-to)252-256
Number of pages5
JournalJournal of Steroid Biochemistry and Molecular Biology
Volume118
Issue number4-5
DOIs
StatePublished - Feb 28 2010

Keywords

  • Androgen
  • Behavior
  • Estrogen
  • Preoptic area
  • Sexual differentiation

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Biochemistry
  • Molecular Medicine
  • Molecular Biology
  • Endocrinology
  • Clinical Biochemistry
  • Cell Biology

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