‘Cuddle hormone’
Research links oxytocin and socio-sexual behaviors

oxytocin.org : koalas cuddling

by Susan E. Barker

Cupid’s arrows just might be dipped in it, and Love Potion # 9 could be nothing more than a brand-name gimmick. In fact, if it isn’t the master key that unlocks the heart to love, the neuropeptide oxytocin is at least a crucial part of the combination, neuroscientists seem to agree.

But a Binghamton researcher’s work is suggesting that oxytocin, sometimes known as the "cuddle hormone" because of its influence on maternal behavior and pair bonding, may be tied to such pressing socio-sexual problems as eating disorders, pedophilia, and child abuse and neglect.

"These are all speculation," cautions Diane Witt, assistant professor of psychology. "All we know at this point is that in animal models, including non-human primates, oxytocin at the level of the brain plays a role in the expression of maternal, sexual, social, stress and feeding behaviors, as well as learning and memory."

Until 10 years ago, we didn’t even know that the brain contained oxytocin receptors. These receptors mediate these numerous behavioral responses, Witt and others have shown.

Although oxytocin is produced in both males and females and receptors for it are found all over the brains and reproductive systems of both sexes, the name oxytocin is derived originally from the Greek for "swift birth." That’s fitting given that a synthetic form of the substance is currently administered to about 75 percent of all women entering labor and delivery rooms in the United States to induce or speed their labor, Witt said.

Witt doesn’t want to make broad-brush criticisms of this practice until the basic research is completed. But she does count herself among "the increasing number of researchers who are leading the crusade to think twice before putting an oxytocin line in," she said.

Among other things, oxytocin, which is produced naturally in the hypothalamus in the brain, stimulates uterine contractions, and allows the breasts to "let down" milk in pregnant and lactating women. The hormone is naturally released in response to a variety of environmental stimuli including nipple stimulation in lactating women, and uterine or cervical stimulation during sex, or as the result of a baby moving down the birth canal.

In China, which enjoys a far lower birth-related morbidity rate than the United States, cool showers, which would stimulate the nipples and cause the brain to release its own oxytocin, are advised when labor needs a boost. In the United States, too, midwives have long known the benefits of applying ice to the nipples of women whose labor is stalled, Witt said.

These natural means of releasing oxytocin have several advantages over intravenous injections of the hormone, Witt said.

First, you avoid the risk of an overdose, which can cause the uterus to contract so severely that the baby cannot be delivered normally.

"Birth does not progress with a tonically contracted uterus," Witt said, "so with excessive amounts of oxytocin, you can actually make the immediate situation worse." But of possibly greater concern, Witt said, is this simple fact: Until researchers are able to more accurately establish how and where oxytocin affects the brain-and, ultimately, human behavior-short-term oxytocin therapy could be having long-term unknown consequences for mothers, their children and society at large.

"In order to understand a pathology, you first have to understand what the normal condition is,” Witt said. “We’ve just begun studying the normal condition and have found, for instance, that oxytocin plays a key role in bonding, even in species that are known to be anti-social."

Oxytocin is a pro-social hormone that affects the brain as a result of its interactions with gonadal steroids like estrogen, progesterone, testosterone and corticosterone.

"The brain affects behavior, but behavior also affects the brain," Witt said. "The brain is very plastic and these gonadal steroids provide a certain milieu in which other chemicals, like oxytocin, can affect the brain."

Animal studies, from Witt’s lab and others, have shown that oxytocin can have dramatic effects on behavior. When the natural release of oxytocin is blocked, for instance, mothers - from sheep to rats - reject their own young.

Meanwhile, virgin female rats injected with oxytocin fawn over another female’s young, nuzzling the pups and protecting them as if they were their own.

In addition, studies show that oxytocin in females, as well as the closely related vasopressin in males, is key to pair bonding.

"You first meet him and he’s passable," Witt said of the phenomena. "The second time you go out with him, he’s OK. The third time you go out with him, you have sex. And from that point on you can’t imagine what life would be like without him."

"What’s behind it?" she added. "It could be oxytocin."

Since the release of oxytocin can be classically conditioned, after repeatedly having sex with the same partner, just seeing that partner could release more oxytocin, making you want to be with that person all the more, and you bond, she said.

But just as oxytocin is linked to the positive aspects of bonding, Witt thinks there’s every reason to suspect that pathological conditions - situations in which bonding breaks down or is established inappropriately -might well be linked to oxytocin, too.

"If there is a pathological condition -that is, if there is too much oxytocin or a heightened sensitivity to oxytocin - there could be inappropriate pair bonding such as pedophilia," she said.

Conversely, too little oxytocin or a reduced sensitivity to it could also be one of several factors in maternal child abuse or neglect, Witt said.

Stripped of the buffer afforded by "mother love," mothers could be indifferent to their children or could quickly come to see their children as burdensome or worse.

So how does this relate to the use of oxytocin in delivery rooms?

"If we are altering the normal system, that affords the opportunity for a pathology to occur," Witt said. "And it’s not just the mother being exposed to it, but the baby, in whom it could later show up as problems."

"Of course," she added, "it could work the opposite way, it could make things better. We just don’t know at this point."

What Witt does know is that when the brain is exposed to overdoses of chemicals like oxytocin or other neurotransmitters, the numbers of available brain receptors for that chemical decrease while the sensitivity of remaining receptors may increase.

That kind of see-sawing makes it all the more difficult for researchers to gauge what’s really going on. Neuroscientists such as Witt track excitatory and inhibitory responses by scanning brain tissue for the appearance of immediate early genes (IEGs), which are markers of neuronal activity.

By figuring out where in the brain IEGs are "lighting up," researchers can begin to determine what brain regions are regulating behaviors that might be affected by specific chemicals.

Witt, who recently finished working with a one-year $40,000 National Institutes of Health grant, is particularly interested in how progesterone and oxytocin interact or "talk to one another in specific brain regions."

She is currently awaiting word on four substantial new grant proposals that would help to advance her work in this area. One of her proposals is to the Environmental Protection Agency and involves a cross-disciplinary project in which she would work with Binghamton University chemist Omowunmi Sadik to try to determine environmental influences that disrupt hormonal activity in the brain.

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