Oxytocin: What is love?

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This Valentine’s day, you might be feeling extraordinarily giddy and happy with your main squeeze, or possibly a little irate or gloomy about not having someone to give candy and flowers. In any case, the concept of love has probably crossed your mind at some point today. What is love? Is there such a thing as “true love?” Will there ever be a person willing to put up with my annoying habits? The answer to these questions could lie in a hormone called oxytocin that is responsible for many of the emotions we feel associated with the word love.

What does oxytocin do?

Oxytocin is the reason we feel butterflies when the cute guy or girl across the room smiles at us. It is responsible for the warm fuzzy feelings we get when someone hugs us. It is also to blame for the sorrow and despair we feel when trust is broken.

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Oxytocin is also the reason for the strong maternal bond that humans have with their children. It is released during childbirth and breastfeeding. Most, if not all of oxytocin’s intended functions are related to human reproduction.

Oxytocin also has many medical uses because of its uplifting properties. It is sold synthetically under the name Pitocin to treat depression and to induce labor. Recently it has also been explored to treat autism after a study showed that people with autism displayed lower levels of the hormone than people without autism.

Oxytocin is one of the many hormones secreted by the pituitary gland. Hormones are produced in glands to tell your body to perform certain activities like digestion, growth, mood, and in the case of oxytocin, reproduction. When we do something that our bodies like, our brains release dopamine to make us feel good and tell us we should do it again. Dopamine is a neurotransmitter that can influence addictive behavior, outlined in last week’s post on sugar.

In the case of love and sex, dopamine triggers the release of oxytocin into the blood which binds with oxytocin receptors. When oxytocin binds it causes a strong bond to the person who caused the dopamine to be released (usually a sexual partner or baby). New research suggests that oxytocin is the reason that humans display monogamous behaviors in addition to maternal bonding. The video below does a great job of describing the relationship between love and the brain.

The reason for “til’ death do we part”

New studies have shown that oxytocin is responsible for monogomous relationship behavior in humans. Humans are one of the few species that exhibit monogamous behavior because from the standpoint of evolution it is advantageous for male species to spread their genes to as many partners as possible. Very little is known about the neurobiological reasons for humans to stay loyal to one sexual partner.

Another animal exhibiting monogamous behavior is the prairie vole. Studies on prairie voles have shown that oxytocin is released in the brain after mating. The voles form a partner bond with their mate after the interactions of dopamine and injected oxytocin. On the contrary, when female prairie voles were injected with an oxytocin antagonist they displayed no affection toward their male counterpart. 

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In a study done with 20 men, data revealed that oxytocin contributes to romantic connections by making them perceive their partner as more attractive than other women. After oxytocin treatment, the men perceived their partner to be increasingly attractive, displayed by a rise in neuroactivity. However, when shown pictures of unfamiliar women, there was no increase in neuroactivity. In other words, the pleasure areas of the brain lit up when they saw a picture of their partner, while pictures of the unfamiliar women showed suppressed feelings of pleasure.

Why would monogamy be beneficial to humans? Scientists think that the reason humans display pair bonding to their sexual partners is due to the decay in oxytocin over time in a relationship. Monogamy evolves in species because of the amount of work it takes to nurture offspring. Human offspring are more difficult to raise than other animals, so it took the work of two parents to raise a child when humans were evolving. Luckily in modern times, we have more access to resources to make raising children a possibility with one parent.

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Oxytocin is a strong and wonderful chemical. It makes us feel human. Whether or not you have a valentine today, go out there and make some oxytocin! Hug a friend, spend time with family, and get those feel-good fuzzies. Here’s to love!

Thanks for reading, and cheers to your brain!

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References:

Lee, Heon-Jin, Abbe H. Macbeth, and Jerome H. Pagani. "Oxytocin: the great facilitator of life." Progress in neurobiology 88.2 (2009): 127-151.

Scheele, Dirk, et al. "Oxytocin enhances brain reward system responses in men viewing the face of their female partner." Proceedings of the National Academy of Sciences 110.50 (2013): 20308-20313.