The ovine sexually dimorphic nucleus, aromatase, and sexual partner preferences in sheep.
Level 5 - mechanism / opinion, no new human data
Animal mechanistic research and narrative review
PubMed 19883759 · doi:10.1016/j.jsbmb.2009.10.009
What was done
This review summarized experimental studies in domestic sheep investigating the role of aromatase and the ovine sexually dimorphic nucleus (oSDN) within the medial preoptic nucleus in relation to sexual partner preference. It examined neuroanatomical differences between female-oriented rams, male-oriented rams, and ewes, as well as the effects of prenatal testosterone exposure on fetal lamb brain organization at approximately day 135 of gestation.
What was found
Aromatase expression is enriched in the oSDN. The oSDN was 2-3 times larger in female-oriented rams than in male-oriented rams, with male-oriented rams having volumes similar to ewes. These differences were not influenced by adult serum testosterone levels. In fetuses at approximately day 135 of gestation, the oSDN was present and approximately 2-fold larger in males than in females. Exogenous testosterone exposure in genetic female fetuses during the critical period masculinized oSDN volume and aromatase expression.
Why it matters
These findings identify a structural and neurochemical correlate of sexual partner preference in a mammalian model and provide evidence that this brain region is organized prenatally by androgen exposure rather than adult circulating hormones.
Limits
The abstract describes animal research in sheep, which cannot be directly extrapolated to human sexuality. Specific sample sizes, variance measures, and experimental protocols from the underlying primary studies are not provided in the abstract.
Cited by
- supports Male-oriented rams show structural and neurochemical differences in the preoptic area of the hypothalamus compared to female-oriented rams.