EP14. ALL YOU NEED IS...OXYTOCIN: BIOCHEMICALS USURP THE DIVINE

Kevin Sharpe

In the summer of 1848, an explosion shot a steel rod through the brain of Phineas Gage, the supervisor of a gang laying railroad tracks in Vermont. He recovered, physically. Before the incident he was even-tempered with a strong, ambitious, social, and positive character. Afterwards, despite emphatic admonitions, his language became so foul that women were advised to stay in his presence for only a few minutes. He was fitful and irreverent, obstinate, unable to stick at anything for long, and indifferent to other people. From the accident he lost the sight of his left eye, and his sociability.

A child in school steals, cheats, fights, and lies. No matter what adults try, they can't change him into a responsible and loving boy. Teachers blame his family background; parents call for a special educational program; counselors work on building self-esteem. The current system considers outside intervention the cure. But does the problem lie outside or inside the boy?

NA natural chemical called oxytocin is found to underlie love,Z says Robert Wright (Wright 1994, 351).

Inside your brain lies your hypothalamus, the organ that controls your primitive behaviors of sex, aggression, and feeding. It produces the hormones oxytocin and vasopressin, and sends them to your posterior pituitary gland for storage and secretion. When released, these biochemicals bind to receptors, specific targets in your brain and elsewhere, like keys fitting into locks. The receptors then effect other body parts and finally your behavior.

Marking territorial boundaries with scent, a specifically male function of certain animals, involves vasopressin. It also helps maintain the volume of water in your body, and the concentration of dissolved substances in your body's fluids, at their respective levels.

Oxytocin naturally stimulates contractions in the uterus right through the birth process by locking onto specific receptors in the muscles of the uterus, causing them to contract. Obstetricians inject a synthetic form of oxytocin to stimulate the contractions when labor flags. It also helps control excessive bleeding after delivery. Within seconds after her baby begins to suckle, oxytocin prompts the mother's mammary glands to release milk. Even the cry of a hungry baby can prematurely stimulate milk let-down, so susceptible is oxytocin release to emotions. It also plays a role in coitus, nipple eroticism, the milk ejection reflex, and female sexual responsiveness.

The uterus, not the hypothalamus, produces the oxytocin that prompts labor, so medical research recently discovered. And to knock out the contractions of premature labor, inject an oxytocin antagonistsa synthetic copycat protein that occupies the receptor, elbowing out the real thing and thus blocking the effects its receptors induce. Not surprisingly, the name of the hormone derives from the Greek for Nswift birth.Z

Other recent research with vasopressin and oxytocin enters fields other than medicine.

When first presented with pups, a virgin female rat usually ignores them, or is frightened of them, or eats them. She will tolerate them only when introduced to them many times over several days. Then she may care for the youngsters by licking them, retrieving them when they stray from her side, and crouching over them protectively. But a pregnant rat responds to pups caringly within minutes, even before delivery of her own. In a classic experiment, virgin female rats were injected with blood from rats that had just given birth; it took the virgins a lot less time to nurture pups than normally. In another experiment, parent rats were injected with antagonists to block their oxytocin receptors. They mistreated their offspring. Oxytocin release also induces grooming behavior in rats, and when injected into sociable mice, it boosts the instinct for cuddling to a frenzied pitch.

Voles are small, brown, nondescript mammals which live under seeds and grasses. Members of one species, the prairie vole, share elaborate systems of burrows and feeding tunnels. Males and females form long-lasting bonds, unlike most rodents, raising their young together. Montane voles occupy separate burrows and avoid each other except to mateswhich they do often and indiscriminately. Mother montane voles usually abandon their pups sixteen days after birth, and fathers never see their offspring. When a predator plucks a youngster from its nest, it neither calls for help nor surges with stress-related hormones. In comparison with their prairie cousins, the high-meadow montane voles lack family values and are exceptionally asocial. Why?

If you map the oxytocin receptors of vole brains to see where the hormone acts, you find many more in key areas of prairie brains than in montane's. And during the brief period in which female montane voles nurse their young, the number of their oxytocin receptors surges. Thus the distribution pattern of oxytocin receptors matches with monogamy and care for offspring.

A female prairie vole copulates with a male repeatedly, more than fifty times over 36-48 hours, as soon as she reaches sexual maturity. After such a bout, she becomes socially exclusive, preferring her mate to unfamiliar males. Mating instills long-term pair bonding. Copulation causes the release of oxytocin; is this the critical factor in developing her social preferences? A female prairie vole rapidly forms a preference for a male if exposed to oxytocin for six hours. But when administered with an antagonist to block the oxytocin receptors, oxytocin ceases its social effect. Oxytocin causes rodents to form monogamous pairs, shaping their sexual and parental behavior, and their social organization.

As a lamb moves down its mother's birth canal, it stimulates nerves that trigger the release of oxytocin. Only with it present at birth or injected so it reaches the brain the same time mother ewe meets her newborn, does she bond with her offspring. She rejects her lamb if something blocks its release. High levels of oxytocin also occur in her milk, suggesting the hormone helps forge a mutual attachment between the mother and her infant.

What about males' sexual and parental behavior? After the initial sexual bout, a male prairie vole prefers his mate and ferociously guards against rivals, even in her absence. When injected with vasopressin, a male isolated from females becomes aggressive and attacks other males, and, if also exposed to a female, develops a preference for her even if they don't mate. Administering a vasopressin antagonist to a male ready to mate doesn't prevent repeated and intense copulation. But afterwards he doesn't fend off intruders or prefer his partner. On the other hand, an oxytocin antagonist alters neither the male's mate preference nor his guarding behavior. Vasopressin also increases (and a vasopressin antagonist decreases) the amount of time he spends with his pups, retrieving and huddling over them; such paternal care for the young anchors, many biologists believe, male monogamy. Only vasopressin, then, accounts for male sexual and parental behavior.

While oxytocin encourages social contact, vasopressin compels the males' antisocial, guarding behavior; they counter each other. Perhaps oxytocin blocks the unfriendliness induced by vasopressin. In many species, vasopressin and oxytocin together determine if a pair bond, exhibit parental care and nurture, and defend the family. Monogamy and polygyny express the net outcome of what happens when oxytocin and vasopressin activate different circuits in the brain.

What about in humans? The human brain manufactures vasopressin and oxytocin which bind to receptors there; our forebrain contains many oxytocin receptors. Thus the hormones could in principle influence our social behavior.

Maternal behavior in an expectant mother arises from hormonal changes that her system induces, and after birth it stems from hormones her offspring stimulates. A sensitive period for this bonding occurs an hour after birthswhen her oxytocin level rises markedly. Breast feeding causes some of the stimulation, and the hormones released by it benefit the mother's mental health and her ability to deal with stress. They calm her.

Vasopressin enters the bloodstream of human males during sexual arousal, and oxytocin at orgasm. Oxytocin levels in both genders rise dramatically during sex, promoting the associated feelings of love and infatuation. A simple touch can release oxytocin. We share many oxytocin and vasopressin responses with other animals.

According to Webster's New World Dictionary, love is Na deep and tender feeling of affection for or attachment or devotion to a person or persons;...a feeling of [unity and cooperation] and good will toward other people;...a strong, usually passionate, affection of one person for another, based in part on sexual attraction.Z Oxytocin fosters friendship, love, and nurturance. With vasopressin, it provides the chemistry of human attachment: sticking with your sexual partner and attention to your offspring. Says Cort Pedersen, NHuman relations are influenced by the model of the parent-child relationship in that they include the notions of nurturing, care, helpZ (Schrof 1991). These behaviors we call love. Love derives from the positive effects of oxytocin and vasopressin.

NChildren need love,Z writes Harold Hulbert in the Reader's Digest, Nespecially when they do not deserve it.Z Sometimes we love despite ourselves, and the involuntary release of oxytocin serves well the survival of our offspring, and with them, our genes. Can we decide to love, and do so? This is the crucial question. Though oxytocin and vasopressin from the hypothalamus mandate social attachments among voles, they and other hormones don't fully determine what happens. No hormone acts alone. A mother's behavior and experience, for instance, both affect and are affected; exposure to pups reorganizes the neural pathways in a mother rat's brain, making her respond faster to pups in the future no matter what her hormone level. A human mother can make her milk let-down just by thinking about it; the thought spurs the release of oxytocin which in turn primes her mammary glands. Many factorssespecially the complex activities in our cerebral cortexsintrude on the effects of the hormone in humans. Love is an adaptive trait, both a willed and an involuntary phenomenon (often a combination of both), but it always involves the release of biochemicals.

Excessive amounts of oxytocin in the brain feature in a type of obsessive-compulsive disorder, the sort that sparks fears of germ contamination that lead to hours of hand washing each daysto the point of rubbing off skin and disrupting all other activities. So oxytocin induces negative effects and only sometimes can we associate it with love. (You could look at the disorder, though, as a way of over-caring, carrying the usual results of oxytocin to an extreme.) It is appealing to ascribe the love role to oxytocin, but it is difficult to prove a causal association objectively, especially with such a large number of variables. Further, the roles of vasopressin and oxytocin are difficult to document, even in animals, and many questions remain unexplored or only partly explored. We need to be cautious when we extrapolate data derived from animal or limited human studies. The important point, though, is that love has a biological rootedness, despite what else it involves.

The dictionary also defines love as NGod's tender regard and concern for [hu]mankind.Z NLove is from God; everyone who loves is born of God and knows God. Whoever does not love does not know God, for God is love,Z writes Saint John (1 John 4:7-8, The New Testament and Psalms: An Inclusive Version). Jesus talks of his wanting to gather together the people of Jerusalem Nas a hen gathers her brood under her wingsZ (Matthew 23:37). The Gospel of John compares the love of the Divine to a good shepherd who would die for the sheep (John 10:17). Parental, filial, altruistic love the oxytocin/vasopressin behaviorsoriginates in the Divine. We meet a confusion: the hormonal behavior arising from the biology of our bodies also originates with the Divine. It has two different sources.

Not only does the Divine love us, but the New Testament urges us to love one another. If love derives largely from involuntary releases of biochemicals, is it reasonable to urge people to love each other? Could Gage, the man with a hole through his head, have changed his ways? These difficult questions challenge the traditional view of the nature of the Divine and the Divine's relationship to us humans.

What is a spiritual understanding of love in the light of this new research? What role does the Divine play in love? An answer could take several paths. It could justify the elevation of love from the animal to the level of the Divine. Or it could make sense of how a divine property could become one that, with its biochemical associates, biological beings experience. Or it could start its understanding of the Divine from scratch, asking anew what is the nature of the Divine.

Whatever, an answer should emphasize the relevance of scientific and spiritual ideas for each other. This means actively exploring such points of contact as the nature and origin of love, its connection with the Divine, and the relationship between the Divine and human beings. In the larger enterprise of the partnership between scientific and spiritual ideas, it means working out a flexible system of spiritual ideas that moves with scientific advances, that builds on the findings of science and adopts a method like science's. It means exploring the spiritual scientifically, offering hypotheses and insights for scientific scrutiny. And it means promoting a science that seeks advances in spiritual thought. Spiritual thinkers and scientists could see themselves working in tandem with each other.

Social bonds have a biology. Love is in part a physical trait derived from evolution, which raises questions about its association with the Divine. To say that the Divine's relationship with the universe and humans is or is like love, however, requires serious reconstruction and justification.

SELECT BIBLIOGRAPHY

Bower, B. 1994. "Hormone Shows Link to Some Obsessions." Science News 146 (29 October):277.

Carter, C. Sue, and Lowell L. Getz. 1993. "Monogamy and the Prairie Vole." Scientific American 268 (June):100-06.

Ezzell, Carol. 1992a. "Explanation for Premature and Delayed Labor." Science News 141 (13 June):389.

------. 1992b. "Brain Receptors Shape Voles' Family Values." Science News 142 (4 July):6-7.

Hrdy, Sarah Blaffer, and C. Sue Carter. 1995. "Hormonal Cocktails for Two." Natural History 104 (December):34.

Insel, Thomas R., and C. Sue Carter. 1995. "The Monogamous Brain." Natural History 104 (August):13-14.

Radetsky, Peter. 1994. "Stopping Premature Births Before It's Too Late." Science 266 (2 December):1486-88.

Schrof, Joannie M. 1991. "Hormone of Love: The Chemistry of Romance and Nurturance." U.S. News & World Report 110 (24 June):62.

Wright, Robert. 1994. The Moral Animal: The New Science of Evolutionary Psychology. New York: Pantheon Books.

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