Research Points to Brain Chemistry as Influencing Sexuality

by Kilian Melloy

EDGE Staff Reporter

Tuesday March 29, 2011

Researchers say that by controlling serotonin levels in the brains of laboratory mice, they have been able to influence sexual behavior. But, they warn, it is far too early to conclude that manipulating human brain chemistry can change sexual orientation.

A March 27 LiveScience.com article says that genetically engineered male mice unable to produce their own serotonin exhibited more same-sex courtship behavior, mounting other males and "singing" to them at frequencies too high for the human ear to detect--another part of the mouse mating ritual.

"Serotonin is known to regulate sexual behaviors, such as erection, ejaculation and orgasm, in both mice and men," the article said. "The compound generally dampens sexual activity; for instance, antidepressants that increase the amount of serotonin in the brain sometimes decrease sex drive."

The article said that mice with normal serotonin levels "mounted females first," but that "nearly half" of the mice lacking the brain chemical "clambered onto males before females," and went on to report that when the mice were given injections to enable them to produce serotonin, they then "mounted females more than males." However, if the serotonin levels climbed too high, the result was a reduction in "male-female mounting," the article said.

"An unavoidable question raised by our findings is whether [serotonin] has a role in sexual preference in other animals," the researchers wrote in a paper that was published in science journal Nature on March 24.

Florida State University's Elaine Hull told LiveScience that the results may have some bearing on the mysteries of human sexuality, but added, "A lot of people are going to be reading more into this than may or may not be warranted." Hull warned that further research was called for, and warned against "jump[ing] to the conclusion that serotonin is the factor that inhibits male-to-male attraction."

Much has been made in the last two decades over the concept of a so-called "gay gene." Though it is unlikely that any single gene will be identified that controls sexual orientation, it is almost certainly the case that genetics plays a role.

Intriguing research carried out in Korea last year shows that there might indeed be a genetic basis for homosexuality, at least in mice--not by the presence of a specific "gay gene," but rather due to the deletion of a gene.

When Korean researchers deleted a gene in laboratory mice relevant to a specific enzyme, fucose mutarotase, what they ended up with were female mice whose sexual behavior focused on other female mice, due to a "masculinization" of their brain structures, reported Neuroscience on July 15, 2010. The female mice shunned sexual contact with male mice, and displayed sexual interest in other females.

"The mutant female mouse underwent a slightly altered developmental program in the brain to resemble the male brain in terms of sexual preference," stated Professor Chankyu Park. Professor Park led the research, which took place at the Korea Advanced Institute of Science and Technology in Daejon, South Korea, reported U.K. newspaper The Daily Telegraph on July 8, 2010.

Similar brain structure differences have been theorized to account for gay and lesbian humans. Scientists suspect that in utero hormone levels play a role in the development of human fetuses that later develop into gay or lesbian adults. Several studies have confirmed a slight, but definite, increase in the incidence of homosexuality in children whose mothers have already given birth to male offspring.

Though changing the hormone balance in the human brain in the same way would probably not lead to a "masculinization" of human neural pathways--the specific hormones that appear to govern human brains and related sexuality are different than in mice--it is possible that an analogous genetic change could have a similar impact of human sexuality. However, a genetically based "cure" (or prevention) for gay humans also seems questionable, since human sexuality could be the result of a confluence of factors.

It is an open question how society might be affected by the eventual discovery of a "gay gene," or even a number of genes interacting in a way that leads to gays and lesbians, rather than heterosexuals, developing. Gay volunteers for a study looking at genetic factors for homosexuality expressed a hope that if a scientific basis in genetics were discovered for homosexuality, the claim--prevalent among religious conservatives--that gays "choose" their sexual orientation would be put to rest once and for all. Were that to be the case, social and legal restrictions on gay equality--such as marriage--might disappear.

However, it is as unlikely that society will change on a dime as it is that a single gene will be discovered that accounts for all or most cases of human homosexuality. An Associated Press Article from Oct. 28. 2007, that reported on the study also carried a quote from Exodus International leader Alan Chambers, who claims to be a former gay man himself. Chambers declared that no matter what science proves about the innate origins of homosexuality, genetics "will never be something that forces people to behave in a certain way." Added Chambers, "We all have the freedom to choose."

The Gay and Lesbian Medical Association's Joel Ginsberg told the Associated Press that one concern among GLBTs is that any such discovery of a definitive genetic basis for homosexuality might lead to demands for pre-natal testing to screen out--and possibly terminate--fetuses determined likely to grown into gays and lesbians.

Nature, Nurture... In Utero Medication?

More controversy arose last year due to reports that a drug used on human embryos to prevent the development of ambiguous genitalia might "feminize" fetuses and "prevent" them from "becoming lesbians" later in life.

The medication is administered to women whose children are at risk for congenital adrenal hyperplasia, reported the Los Angeles Times on Aug. 15, 2010. Adrenal hyperplasia involves abnormal function of the fetus' adrenal gland, leading to elevated masculinizing hormones that can affect fetal development and cause the genitalia of female newborns to be ambiguous in appearance--and, there is some indication, also lead to lesbianism once the infants reach sexual maturity.

The medication offered to pregnant mothers can prevent the development of ambiguous genitalia. It might also, the Los Angeles Times article says, promote more "female" behavior in young children. At least one researcher, Mt. Sinai's Dr. Maria New, has reported that there is a higher incidence of lesbianism among women who were born with the condition, and whose mothers did not receive any medication to treat it in utero.

But no one has yet done research that would conclusively prove that prenatal treatments would decrease the number of infants born with adrenal hyperplasia who then grew up to become lesbians. Even so, there are fears that mothers might be prescribed the drug--which carries some risk for side effects--to prevent lesbian offspring as much as to treat adrenal hyperplasia.

Professor of bioethics Alice Dreger worries that the treatment might constitute "engineering in the womb for sexual orientation," and adds that some doctors "suggest that you should prevent homosexuality if you can. But being gay or lesbian is not a disease and should not be treated as such."

Warns pediatric endocrinologist Dr. Phyllis Speiser, "There is not a lot of information on [the] long-term safety" of the medication, which has been linked in animal studies to memory loss, changes in brain structure, and high blood pressure. "The efficacy has been demonstrated in case reports--a fairly sizable number of cases that used untreated siblings for comparison--but not in randomized, controlled clinical trials," Speiser noted.

A colleague and sometime collaborator of Dr. New, Dr. Heino Meyer-Bahlburg of Columbia University Medical Center, noted, "The majority [of people with the condition], no matter how severe [it may be], are heterosexual. But the rate of CAH women attracted to females increases with their degree of androgen exposure during prenatal life."

However, added Dr. Meyer-Bahlburg, "I would never recommend treatment in order to take lesbianism away if that is someone's predisposition." Noted Meyer-Bahlburg, "Any treatment can be misused. That could happen here. But this is not the focus of the treatment."

Not yet, anyway. The report comes in the wake of a 2007 study that indicates that the biological causes of homosexuality--physiological, hormonal, and genetic--may be one day fall within the power of physicians to manipulate. At that point, the question becomes whether it is morally acceptable to change a human being in order to accommodate social or religious preferences regarding innate characteristics such as sexuality.

The 2007 report, published in Nature Neuroscience, showed that by altering the way fruit flies responded to pheromones, the flies could be induced to change their courtship behavior. Flies that had previously courted the opposite sex began to pursue flies of their own gender--while flies that had only shown a predisposition to pursue those of their own gender began to court flies of the opposite sex.

One of the researchers, the University of Illinois at Chicago's Dr. David Featherstone, called the results "amazing," and said, ""I never thought we'd be able to do that sort of thing, because sexual orientation is supposed to be hard-wired. This fundamentally changes how we think about this behavior."

Featherstone told New York Times science writer John Tierney that similar manipulation of sexuality might one day be possible for human beings. "The question of whether or not homosexuality should be turned on and off is not a scientific question. It is an ethical/societal dilemma," noted Featherstone, adding, "I am glad my work is stimulating the discussion earlier rather than later. History is replete with poorly thought out attempts to 'cure' societal/behavioral 'illnesses' that turned out, with proper perspective, to not be 'illnesses' at all."

In a follow-up article, Featherstone told Tierney, "The response to our research has been fascinating, and highlights the giant gap between what neuroscientists already know and what the public believes." Added the researcher, "The fact is, 'gay genes' have been known to exist for a long time, in flies and other animals, including humans. Genetic links to all sorts of human traits have been identified."

Featherstone went on to cite research that had suggested similar changes in sexual behavior had been demonstrated in mice, telling Tierney, "So the question is not if we will understand the biological basis of homosexuality enough to alter it, but when. And what people will choose to do with the knowledge. If there is a demand, I guarantee some pharmaceutical company will make the stuff.

"Or will the government outlaw treatments for behaviors that are obviously no threat to the individual or society?" asked Featherstone. "Would this imply that the government officially thinks that homosexuality is no one's business but one's own?"

Tierney speculated that, moral and ethical questions of biological engineering aside, a future in which sexuality can be changed through pharmaceutical means might lead to a greater openness regarding sexual mores, rather than more stringent enforcement of social and religious norms, envisioning a time when individuals truly do choose their sexuality--through chemical means, and for lifestyle reasons rather than moral ones. That could well mean that heterosexuals looking to try something different actually opt to "go gay," Tierney suggested, going on to speculate that social conservatives who otherwise object to science manipulating human beings might make an exception and endorse treatments that would "cure" gays.

The social and ethical questions of "curing" or even identifying gays and lesbians in the womb have been explored already in literature. One notable mediation on the issue is Jonathan Tolins' 1993 play Twilight of the Golds, in which a pregnant couple learn that their baby will probably be gay. The mother decides that she wishes to terminate the pregnancy rather than rear a gay child, but her younger brother--who is a gay man--objects strenuously, only to be told by his own parents that had the same technology been available to them, he would have been aborted as a fetus. The play was made into a 1997 TV movie starring Jennifer Beals, Brendan Fraser, Rosie O'Donnell, and Faye Dunaway.

Kilian Melloy serves as EDGE Media Network's Associate Arts Editor and Staff Contributor. His professional memberships include the National Lesbian & Gay Journalists Association, the Boston Online Film Critics Association, The Gay and Lesbian Entertainment Critics Association, and the Boston Theater Critics Association's Elliot Norton Awards Committee.

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