Sexy science: Could this be a love potion that works?

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It's known that the chemicals oxytocin and vasopressin are linked to feelings of closeness, and have an profound effect on social interaction and intimacy

IT INDUCES warm feelings of trust and social connectedness and has been called the love hormone. Wouldn't it be nice, then, to spray a bit of the brain chemical oxytocin around in your home or office to keep relationships harmonious and arguments at bay?

Seriously, though, teams of scientists in different parts of the world are in a race to develop forms of oxytocin for clinical use in treating problems involving social interaction such as shyness, anxiety and even autism. Paul Zak of the Center for Neuroeconomics Studies in Claremont, California, has called it "the glue of society". In a study published in the journal Nature, Zak showed that people given a dose of oxytocin become more generous and trusting.

Oxytocin has its effect by dampening activity in a part of the brain called the amygdala, which is responsible for our feelings of fear. It also has an effect on the reward centres in the brain.

The hormone has long been known for its role in helping mothers bond with their babies, but more recently we've learned that it helps in more grown-up bonding too.

Studies of voles (small rodents) have shown that oxytocin and a closely related chemical, vasopressin, are released during mating and are important in creating bonds between the mated male and female. In humans too, large amounts of these hormones are released by the brain in both men and women as they climax during sex, and it seems likely that they could have a similar bonding function in us.

Women vary hugely in their tendency to reach orgasm during sex. Could it be that the man who fully satisfies his lover is the one she falls in love with because of the oxytocin pumping round her brain's pleasure centres?

Well, it's unlikely to be anything like that simple, since women's oxytocin levels vary as much as their orgasm experiences. In her book, The Case of the Female Orgasm, Elisabeth Lloyd, a science philosopher from Indiana University, presents data showing that some women's baseline oxytocin levels during sex were far greater than other women's levels following orgasm. It's hard, therefore, to know whether a woman's orgasm during sex, or lack of it, is more important than simply sex itself for creating a feeling of intimacy with their partner.

Not everyone agrees with her, but Lloyd thinks that orgasm in women doesn't have an evolutionary function at all and is simply a vestige, like male nipples, of the parallel development of male and female embryos. Female orgasms, she says, are just for fun. Excellent.

Going back to the voles, it's the number and distribution of oxytocin and vasopressin receptors in their brains rather than the amount of the hormones themselves that turn out to be important. In prairie voles, males have lots of vasopressin receptors and they stay faithful to their mate. Montane voles, on the other hand, have far fewer receptors and are on the very frisky side.

Considerable variation exists in the vasopressin receptor gene in humans according to a study by Dr Larry Young of Emory University, Atlanta. This makes me wonder if men could vary genetically in their ability to stay faithful to one partner. But the way we behave depends on our life experiences and environment as well as on our genes, so if you get caught playing away guys, don't try blaming it on your receptors.

The big question though is – could we use oxytocin as a love potion? It's easy to buy online as a nasal spray. If we could just surreptitiously squirt some of the stuff up our partner's nose during a lovemaking session, could that bring on a feeling of commitment or perhaps a marriage proposal?

Sadly, it's not quite that easy. A big problem is that oxytocin's effects are short-lived so the feelings wear off if the oxytocin supply dries up. However, pharma companies are eagerly trying to find a chemical that can get into the brain and switch on oxytocin receptors long-term. Whoever wins that race that may have come up with the ultimate elixir for producing that lovin' feeling.