Hormonal influences on sexual partner preference in rams
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Updated: Sep 29, 2026

Measuring In Vivo Changes in Extracellular Neurotransmitters During Naturally Rewarding Behaviors in Female Syrian Hamsters
Published on: September 12, 2017
Charles E Roselli1, John A Resko, Fred Stormshak
1Department of Physiology and Pharmacology, Oregon Health Sciences University, 3181 S.W. Sam Jackson Park Road, Portland, Oregon 97201, USA. rosellic@ohsu.edu
Abstract:
Domestic rams display a naturally occurring variation in sexual partner preference, such that 6-10% of range-bred populations prefer male sexual partners (male-oriented) in contrast to the majority of rams that prefer female sexual partners (female-oriented). Male-oriented rams exhibit hormone profiles and stress responses distinctly different from their heterosexual counterparts. These differences include reduced circulating levels of testosterone that arise after anesthetization. Lower levels of aromatase activity in the medial preoptic area and estrogen receptor in the amygdala were also measured in male-oriented versus female-oriented rams and may represent an important link to sexual behavior that should be investigated. It is anticipated that the male-oriented ram model will be useful for studies aimed at identifying both the activational and organizational components and the neuronal substrates of male sexual partner preferences.
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