Above: Composite image by Meredith Hanel, using Kiss of love by gubgib at FreeDigitalPhotos.net and CPK model of the Oxitocin molecule C43H66N12O12S2 by Mindzipper
Fast fact: “Oxytocin” combines the Greek words oxus (swift) and tokos (birth). Sir Henry Dale, who discovered that the hormone caused contractions in the uterus of a pregnant cat, coined the term in 1906.The age-old question of why we fall in love has long been pondered by artists and philosophers. More recently, scientists have taken a crack at solving this complex puzzle. Researchers theorize that one component, the feeling of attachment that makes people in love want to spend so much time together, actually evolved as a way of keeping couples together. That way, they could enjoy the advantages of having the father help raise young and protect the family.
Even though human couples do not always stay together for life, scientists believe that the same brain chemicals that make some animals monogamous may control romantic attachment in humans. Oxytocin, dubbed the love hormone, is crucial for monogamy in prairie voles. It has also received a lot of attention as a possible mediator of (influence on) bonding in human couples.
To identify brain signals associated with bonding, scientists looked for differences in brain signals between the prairie vole, an animal that mates for life, and the closely-related but promiscuous Montane vole. Oxytocin is a brain messenger that binds specific receptors, like a key into a lock, to activate certain brain regions. It turns out that the female prairie voles have oxytocin receptors in areas of the brain that release dopamine. The dopamine causes her feel good when her mate is around. By contrast, the Montane vole’s brain does not respond to oxytocin in the same way. Dopamine is also triggered by highly addictive drugs, which may explain why love can feel like an addiction.
Fast fact: The release of oxytocin helps mothers produce milk.Does oxytocin influence human bonding? People who gaze at a picture of their sweethearts do activate the oxytocin receptor areas in their brains, as measured by fMRI (functional magnetic resonance imaging). This supports (but does not prove) the hypothesis that oxytocin mediates bonding in human couples.
Interestingly, fMRI studies show similar patterns in cases of both romantic and maternal love. Since oxytocin is also an important influence on maternal-infant bonding in animals, it is possible that bonding in couples evolved from the maternal-infant bonding system.
In female prairie voles, oxytocin is released after the first mating encounter, causing a lifelong bond with her mate. Researchers found that infusing a female prairie vole’s brain with oxytocin in the presence of a male acted like a love potion, creating a bond even though the animals had not mated.
Fast fact: Because oxytocin decreases fear and promotes social bonding, it is being investigated as a potential treatment for some mental disorders that affect a person’s ability to interact socially. Examples include autism, schizophrenia, anxiety, and post-traumatic stress disorder.Research suggests oxytocin could act as a love potion in humans too, since people who sniffed oxytocin rated individuals in randomly selected images as more attractive or trustworthy. A company called Vero Labs actually markets oxytocin in a spray that you can wear like cologne, calling it “liquid trust.” The company boasts that their product will help build both business and romantic relationships, but these claims have not been verified.
Regardless of whether love potions are real, understanding oxytocin and other brain messengers that control different aspects of love—from sex to social behaviour—will continue to interest scientists because they affect our happiness and well-being.
General news and science websites
Love & Sex: The Vole Story (Kate Egan, Emory Medicine)
http://whsc.emory.edu/_pubs/em/1998summer/vole.html 'Love Hormone' Oxytocin Shows Promise for Treating Mental Illness (Rachael Rettner, My Health News Daily)
http://www.myhealthnewsdaily.com/608-oxytocin-therapy-psychiatric-illness-101205-.html Love Potion Number 10: Oxytocin Spray Said to Increase Attraction (Boonsri Dickinson, Discover Magazine)
http://blogs.discovermagazine.com/discoblog/2009/04/14/love-potion-number-10-oxytocin-spray-said-to-increase-attraction/ Oxytocin: is it really a trust hormone? Maybe we should choose who to trust (The Guardian)
www.guardian.co.uk/science/blog/2012/jul/03/oxytocin-trust-hormone The Science of Love (BBC)
Borrow AP, Cameron NM. 2012. The role of oxytocin in mating and pregnancy. Hormones and Behavior. 61:266-276. Carter CS, Porges SW. 2013. The biochemistry of love: an oxytocin hypothesis. EMBO reports. 14(1):12-16. De Boer A. et al. 2012. Love is more than just a kiss: a neurobiological perspective on love and affection. Neuroscience. 201:114-124. Magon, N, Kalra S. 2011. The orgasmic history of oxytocin: Love, lust, and labour. Indian Journal of Endocrinology and Metabolism. 15(3):S156-S161.