January 19, 2004
Health
THE CUDDLE HORMONE
Endocrinologists have known for years that oxytocin, released by
the pituitary gland, ovaries and testes, helps trigger childbirth
contractions, milk production during nursing and the pelvic
shudders women experience during orgasm (and possibly the
contractions during male orgasm as well). The hormone is believed
to play a vital role in mother-child bonding and may do the same
for new fathers: oxytocin surges when a new dad holds his bundle
of joy. Some researchers also think of oxytocin as a cuddle
chemical. Preliminary studies by psychiatrist Kathleen Light at
the University of North Carolina have found that oxytocin levels
rise after couples hold hands, hug or watch romantic movies. It
also may be what makes you want to stay with your partner until
the morning after sex. Those who can relate to Billy Crystal's
"How long do I have to lie here?" scene from When Harry Met Sally
might question whether oxytocin affects both genders equally.
But there's increasing evidence that oxytocin is also involved in
deeper bonding. It certainly plays that role in a much studied
little rodent called the prairie vole, which is famous for its
fidelity to its mate. The critter's brain releases a rush of
oxytocin as it bonds with its beloved. Block the chemical, and
voles fail to make a connection. Inject more of the hormone, and
they fall for each other even faster.
A similar kind of imprinting might take place in humans.
"Oxytocin release may help us bond to certain features in our
partners," says Pfaus. "It's probably part of the mechanism that
generates the template of what we find attractive." The next time
you see your partner or someone like your partner, he theorizes,
"the oxytocin is activated. It doesn't mean you have to be
aroused. You just think, God, what a beautiful woman"—which
might explain why we're attracted to the same type over and over.
ATTRACTIVE AROMAS?
Probably the most controversial issue in the chemistry of
sexuality is the role of pheromones. In 1971 the University of
Chicago's McClintock, then a Wellesley undergraduate, proved
scientifically what women in dorms had known for decades:
menstrual periods become synchronized when women live together.
It's probably because of pheromones, she said—olfactory
chemicals that we can detect even though we're not aware of them.
In 1998, she did experiments that proved this hypothesis, but,
unlike animal pheromones, no human versions have been isolated.
Because menstrual cycles and sexuality are part of an overall
system, it's possible that pheromones could trigger desire.
Perfumemakers that market pheromone-based scents have latched
onto this notion. It's plausible, says Altman, "but I don't think
the science is very good on it." Pfaus agrees: "I hope it's true.
Totally on faith, I believe it. The problem is that the scientist
in me says, 'O.K., but what are these pheromones, and who has
shown it?'"
A DOUBLE SHOT OF LOVE
A newly identified substance that has captured Pfaus's interest
is alpha melanocyte polypeptide, also known as
melanocyte-stimulating hormone (MSH). In clinical trials, this
pituitary hormone had the dual effect of giving men erections and
heightening their interest in sex. Pfaus is studying a synthetic
version for Palatin Technologies of Cranbury, N.J., which is
developing it as a nasal spray. "It's astonishing that you have a
little peptide that has such a big, specific effect," he says. It
interacts with dopamine, but how, precisely? "We don't know," he
says.
Like all substances that promise to increase desire and
performance, whether they are prescription drugs or folk
aphrodisiacs sold next to the cash register at the quick-stop
store, MSH is tough to investigate because of the placebo effect.
As Procter & Gamble discovered with its testosterone-patch study,
arousal and desire are so entangled with one's state of mind that
it's tough to figure out cause and effect. Says Altman: "If
you're in a tribal society and taught that something is an
aphrodisiac, it probably will be. But someone in Los Angeles
taking the same thing probably won't get the same effect."
Maybe that's just as well. For those who suffer from a lack of
interest in sex, like Roslyn Washington, it's great to have a
treatment that works. But like the women in the testosterone
study who responded to a placebo showed, the real point is to
create a sex life that works. Feeling is believing, and vice
versa. We experience attraction and sexual desire as a sort of
magic, a phenomenon filled with delightful mystery. And if
scientists continue to be overwhelmed by the complex interplay of
dozens of substances percolating from mind to body and back, that
keeps the mystery nicely intact.
— Reported by Sonja Steptoe/Los Angeles
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