Featured Research

from universities, journals, and other organizations

Biology Behind Homosexuality In Sheep, Study Confirms

Date:
March 9, 2004
Source:
Oregon Health & Science University
Summary:
Researchers in the Oregon Health & Science University School of Medicine have confirmed that a male sheep's preference for same-sex partners has biological underpinnings.

PORTLAND, Ore. – Researchers in the Oregon Health & Science University School of Medicine have confirmed that a male sheep's preference for same-sex partners has biological underpinnings.

A study published in the February issue of the journal Endocrinology demonstrates that not only are certain groups of cells different between genders in a part of the sheep brain controlling sexual behavior, but brain anatomy and hormone production may determine whether adult rams prefer other rams over ewes.

"This particular study, along with others, strongly suggests that sexual preference is biologically determined in animals, and possibly in humans," said the study's lead author, Charles E. Roselli, Ph.D., professor in the Department of Physiology and Pharmacology, OHSU School of Medicine. "The hope is that the study of these brain differences will provide clues to the processes involved in the development and regulation of heterosexual, as well as homosexual, behavior."

The results lend credence to previous studies in humans that described anatomical differences between the brains of heterosexual men and homosexual men, as well as sexually unique versions of the same cluster of brain cells in males and females.

"Same-sex attraction is widespread across many different species." said Roselli, whose laboratory collaborated with the Department of Animal Sciences at Oregon State University and the USDA Agricultural Research Service's U.S. Sheep Experiment Station in Dubois, Idaho.

Kay Larkin, Ph.D., an OHSU electron microscopist who performed laboratory analysis for the study, said scientists now have a marker that points to whether a ram may prefer other rams over ewes.

"There's a difference in the brain that is correlated with partner preference rather than gender of the animal you're looking at," she said.

About 8 percent of domestic rams display preferences for other males as sexual partners. Scientists don't believe it's related to dominance or flock hierarchy; rather, their typical motor pattern for intercourse is merely directed at rams instead of ewes.

"They're one of the few species that have been systematically studied, so we're able to do very careful and controlled experiments on sheep," Roselli said. "We used rams that had consistently shown exclusive sexual preference for other rams when they were given a choice between rams and ewes."

The study examined 27 adult, 4-year-old sheep of mixed Western breeds reared at the U.S. Sheep Experiment Station. They included eight male sheep exhibiting a female mate preference – female-oriented rams – nine male-oriented rams and 10 ewes.

OHSU researchers discovered an irregularly shaped, densely packed cluster of nerve cells in the hypothalamus of the sheep brain, which they named the ovine sexually dimorphic nucleus or oSDN because it is a different size in rams than in ewes. The hypothalamus is the part of the brain that controls metabolic activities and reproductive functions.

The oSDN in rams that preferred females was "significantly" larger and contained more neurons than in male-oriented rams and ewes. In addition, the oSDN of the female-oriented rams expressed higher levels of aromatase, a substance that converts testosterone to estradiol so the androgen hormone can facilitate typical male sexual behaviors. Aromatase expression was no different between male-oriented rams and ewes.

The study was the first to demonstrate an association between natural variations in sexual partner preferences and brain structure in nonhuman animals.

The Endocrinology study is part of a five-year, OHSU-led effort funded through 2008 by the National Center for Research Resources, a component of the National Institutes of Health. Scientists will work to further characterize the rams' behavior and study when during development these differences arise. "We do have some evidence the nucleus is sexually dimorphic in late gestation," Roselli said.

They would also like to know whether sexual preferences can be altered by manipulating the prenatal hormone environment, such as by using drugs to prevent the actions of androgen in the fetal sheep brain.

In collaboration with geneticists at UCLA, Roselli has begun to study possible differences in gene expression between brains of male-oriented and female-oriented rams.


Story Source:

The above story is based on materials provided by Oregon Health & Science University. Note: Materials may be edited for content and length.


Cite This Page:

Oregon Health & Science University. "Biology Behind Homosexuality In Sheep, Study Confirms." ScienceDaily. ScienceDaily, 9 March 2004. <www.sciencedaily.com/releases/2004/03/040309073256.htm>.
Oregon Health & Science University. (2004, March 9). Biology Behind Homosexuality In Sheep, Study Confirms. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2004/03/040309073256.htm
Oregon Health & Science University. "Biology Behind Homosexuality In Sheep, Study Confirms." ScienceDaily. www.sciencedaily.com/releases/2004/03/040309073256.htm (accessed July 30, 2014).

Share This




More Mind & Brain News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

It's Not Just Facebook: OKCupid Experiments With Users Too

It's Not Just Facebook: OKCupid Experiments With Users Too

Newsy (July 29, 2014) If you've been looking for love online, there's a chance somebody has been looking at how you're looking. Video provided by Newsy
Powered by NewsLook.com
How Your Face Can Leave A Good Or Bad First Impression

How Your Face Can Leave A Good Or Bad First Impression

Newsy (July 29, 2014) Researchers have found certain facial features can make us seem more attractive or trustworthy. Video provided by Newsy
Powered by NewsLook.com
Losing Sleep Leaves You Vulnerable To 'False Memories'

Losing Sleep Leaves You Vulnerable To 'False Memories'

Newsy (July 27, 2014) A new study shows sleep deprivation can make it harder for people to remember specific details of an event. Video provided by Newsy
Powered by NewsLook.com
University Quiz Implies Atheists Are Smarter Than Christians

University Quiz Implies Atheists Are Smarter Than Christians

Newsy (July 25, 2014) An online quiz from a required course at Ohio State is making waves for suggesting atheists are inherently smarter than Christians. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins