A new study led by Kristin Kramer of the University of Memphis shows that manipulating oxytocin at birth can make changes in the central nervous system that only show up later in life.
There's growing concern that the jolt of pitocin routinely used in U.S. hospital births could have unforeseen consequences. This study provides more ammunition. At the same time, it did not show that high doses of oxytocin interfere with social behavior later.
The study, The organizational effects of oxytocin on the central expression of estrogen receptor alpha and oxytocin in adulthood
, was published online in BMC Neuroscience
on September 7. Kramer, with Shigeto Yoshida, Eros Papademetriou and Bruce Cushing, looked at the effects on estrogen receptors of giving the voles a high dose of oxytocin, an oxytocin blocker or placebo on the day they were born.
They found that the effects of oxytocin depended on the dose, and they differed in the male and female voles.
The caveats: First, the study was done with prairie voles, the cute and monogamous rodents that burrow under the prairies of the Midwest. There's no proof it translates to humans. Second, researchers can't actually see the estrogen receptors; instead, they are making inferences based on the reactions of substances that bind with these receptors.
, chair and director of the Integrated Bioscience Program at the University of Akron has been researching how steroids including estrogen influence the organization of the central nervous system.
His studies, along with those of others, have shown that manipulating oxytocin at birth can change the way adult voles respond in social situations and the way they care for offspring.
His theory is that social interactions during the neonatal period -- mostly care by a vole pup's mother and father, influence later behavior by altering sensitivity to things like estrogen, oxytocin and vasopressin.
Although we think of oxytocin and vasopressin as responsible for social behavior, Cushing says that estrogen is just as important. Specifically, Cushing has found that the distribution of estrogen receptors in male rodents is associated with social behavior.
Highly social males have significantly lower levels of estrogen receptor reactivity than females in the parts of the brain associated with what scientists call "prosocial behavior." Louis Cozolino, author of "The Neuroscience of Human Relationships
," has a great shorthand term for this; he calls the various brain structures "the social brain," and that's what I'm going to use.
Simply, the more sensitive are the estrogen receptors in the male social brain, the less social the animal is. And vice versa.
The strongest effects in the study came from giving the male newborn voles a chemical to block oxytocin's effects. The oxytocin antagonist made the estrogen receptors more sensitive, and decreased social behavior.
My personal, non-scientist extrapolation is that this shows a possible mechanism whereby a lack of nurturing and touch in infancy can create attachment disorders later on.
On the other hand, the researchers didn't see effects from giving a high dose of oxytocin at birth.
Cushing told me, "The problem is that prairie voles are very social already, so giving them extra oxytocin may not do anything. The antagonist blocks the effects of normal endogenous oxytocin. But if you already are very good at something, it may be hard to notice any improvement."
I asked him whether his studies supported the theory that using pitocin during labor can cause lasting, harmful effects. He said he's very conservative about making such extrapolations.
"We have no idea what [pitocin] is doing," he said. "It could cause changes in behavior. We also know there were long-term effects from oxytocin on the female expression of oxytocin receptors. And, just because you don't see changes in the estrogen receptor immunoreactivity, it doesn't mean it doesn't have an effect. But there's a difference between could and does."
He added that science hasn't made the connection between the dose given to the mother and what happens to the infant. It's important to figure that out, but we still don't have any answers.
However, this study does help answer one question: Screwing around with neurochemicals at birth can have lifelong consequences.