Oxytocin, Vasopressin, and the Body’s Theology

Lifeguard Column by Nicolo F. Bernardo

ALTHOUGH the human sciences have always dabbled with the healthy and ill, the “natural” and the “unnatural” in sexuality, anthropologists and biologists of recent seem to have found new affection on cracking the “biochemistry of love.” After all the poetry has been said about romance—whose feast we shall celebrate on February 14—scientists finally have their take on love, with revelations to interest theologians of the body.

The clinical thesis is this: The body’s neuropeptides reveal how love does proceed and what sexual practices could better serve our physiologic interests. John Paul II must be right to say that the Creator’s plan for relationships is imprinted in our bodies (dubbed as the “Theology of the Body”). Our bodily design has got a lot to tell on what true love could mean.

Take for instance our hormone oxytocin. By it we can fairly say how sex, love, and reproduction are meant to rhyme. This “bonding hormone,” as it is called, is present in the continuum of courtship, romance, orgasm, pregnancy, infant nurturing, and breastfeeding. And what oxytocin joined together, let no man put asunder.

Then there is the hormone vasopressin. It is the aggression hormone that makes males protective, jealous, and attentive husbands. Vasopressin helps in laying down memories, in familiarizing with the partner and her kids. Take out this mechanism of jealousy and protectionism and the father would be like any stag, oblivious of who may be his kids or who may be his partner’s partners.

Of course there are many men who behave that way, which only shows that the presence of this or any hormone—or their absence—is hardly deterministic of human behavior. The phenomena of love could not be reduced to a chemical concoction or a biological event, although the body’s chemicals may suggest how a healthy loving person could be.
A study by the Center for Behavioral Neuroscience, funded by the US National Institute of Mental Health, says that oxytocin and vasopressin play key roles in the formation of social attachments between animals, especially for “lifelong pair bonding” or “monogamy.” It might lead us the answer whether we humans are meant to stick to one, since humans, unlike other animals, are high in oxytocin and vasopressin.

It is no coincidence that another mammal high in oxytocin and vasopressin is also monogamous. The prairie vole, unlike its other mice cousins, is a case in point. Oxytocin receptors have high concentration in the nucleus accumbens and the pre-limbic cortex of prairie voles as in humans. Vasopressin receptors are also in large quantities in the ventral forebrain of the prairie vole. The male prairie vole is defensive and exclusive of its partner, while the female prairie vole and her boons are almost inseparable. Together they make a family.

“The oxytocin and vasopressin systems appear to activate two separate nodes of the same reward pathway to form and reinforce pair bonds,” explains Dr. Larry Young, associate professor of psychiatry and behavioral sciences at Emory University School of Medicine (Emory University Health Sciences Center in the study Reward Mechanism Involved in Addiction Likely Regulates Pair Bonds between Monogamous Animals).

Among humans’ fellow primates (monkeys) that have been studied, monogamous marmosets also have higher levels of vasopressin found in the reward centers of their brains than do non-monogamous rhesus macaques.

Remember that in John Paul II’s work Love and Responsibility, love proceeds from phases of “sensuality/sentimentality” to “affection” then to “real love.” These stages agree with our brain’s neuropeptide mechanisms.

Attraction allows people to home in on a particular mate. This state is characterized by feelings of exhilaration, and intrusive, obsessive thoughts about the object of affection. But this romance, sometimes of lust, is unstable, and not a good basis for commitment and child-rearing. The final stage of love, long-term attachment, allows parents to cooperate in raising children. This state, says Dr Helen Fisher, an anthropologist at Rutgers University-New York, is characterized by feelings of calm, security, social comfort, and emotional union (Fisher, Why We Love: The Nature and Chemistry of Romantic Love).

How do you maintain the stimulant of romance for a long time? Fisher holds it possible to trick the brain into feeling romantic in a long-term relationship by doing novel things with one’s partner. These drive up the level of dopamine or the “pleasure hormone” and can therefore trigger feelings of romance as a side effect. Thus, long-term love can be sustained by doing acts of love as exhilarating feelings follow after.

Now about procreation. Oxytocin is the same hormone that works for rearing and reproduction. Not only does the oxytocin mediate females’ retention of the male sperms, it also causes men to sleep and snooze after a sexual act. This seems to work to make the man stay awhile with the woman, to bond longer while asleep, and probably deal with commitment and possible conception the morning after. Interestingly, one cause that helps women deal with and forget the difficulty of pregnancy and childbirth is her oxytocin being secreted into her spinal column during and after labor. Oxytocin is also responsible for her maternal behavior.

With all these mechanisms of oxytocin in mind, we can see why in contraceptive and homosexual sex, the purposes of oxytocin release are frustrated (and precisely why certain contraceptives have to tamper the body’s natural hormones). My former professor in Feminism of the Theology of the Body, Dr. Josephine Acosta-Pasricha of the University of Santo Tomas, used to say that in male to male relationships, the most we have are aggressive vasopressins defaulting together. No wonder why such ties hardly last.

So arguably, we can say that the Christian theology of the body has a biological and anthropological support. Man has the natural components for choosing love, and it benefits him to act on love and life-giving acts. It appears that the mores about fidelity, divorce, abortion, contraception, and homosexual sex came up not just to savor the soul, but to give the body its authentic reproductive health.