GearBits

Addicted to Love

While we're far from conclusively identifying what the secret compound is at the tip of Cupid's arrow, scientists are making fascinating discoveries in the understanding of the chemistry of love.

The tale begins with prairie voles, who are monogamous, and montane voles, who only partake in one-night-stands. Yet the two species are more than 99% alike, genetically.

Two hormones - oxytocin and vasopressin - are released during prairie vole sex. If blocked, prairie vole sex does not lead to lifelong relationships. More amazingly, if prairie voles are injected with the hormones, but prevented from having sex, they still form a preference for the one partner.

In other words, researchers - with an injection - have been able to induce the response of falling in love.

And there's more...

A further clue was that the same injection made no difference to the montane vole. It turns out that the prairie vole has receptors for the hormones in brain areas associated with reward - which reinforces an action - but the montane vole does not.

Another point is that vasopressin and oxytocin - the hormones above - are involved in the brain to pick out the features used to identify individuals. If the genes for oxytocin and vasopressin are suppressed in a mouse, that mouse is a social amnesiac and has no memory of other mice it meets.

So the thesis is that prairie voles form a "image" of their partners - likely with smell - and this image becomes linked with pleasure in the brain. Love, essentially, is an addiction through a process of sexual imprinting mediated by smell.

Research is beginning to suggest that the reward mechanism in this addiction has probably evolved in a similar way in humans.

Vasopressin and oxytocin have been found to have similar responses in humans; and brain scans on people in love have also uncovered some fascinating things.

First, only a relatively small area of the human brain is active in love. Second, the brain areas active in love are different from those active in other states, such as fear and anger

Instead, the active brain areas of people in love are related to the areas which generate the euphoria associated with drugs such as cocaine. The brain scans of people deeply in love do not look like those of people under strong emotions, but instead like those of people taking cocaine. This suggests strongly that love uses the neural pathways activated during the process of addiction.

The vole interaction and the brain scan research both tell a consistent story. We are - literally - addicted to love.