I’ve actually talked about this in the past that they’ve discovered the protiens that cause the “love” to actually happen. Here is some more research via the Register.

Romantic love quickly dies
Brain chemicals - not amoré - linked to passion
By John Leyden
Published Monday 28th November 2005 16:23 GMT

Romantic love normally lasts only a year, according to Italian boffins, whose findings would have Casanova spinning in his grave.

Scientists at the University of Pavia reckon that a brain chemical linked to feelings of euphoria - rather than amoré - in responsible for setting new lovers’ hearts a flutter. Scientists looked at levels of proteins known as neurotrophins in the blood of men and women aged 18 to 31.

The sample included people in both long and short relationships as well as singletons. The researchers found that those starting a relationship experienced increased levels of nerve growth factor (NGF) proteins, which causes sweaty palms and the butterflies, the BBC reports. Boffins found levels of these psychotropic proteins - which they linked to feelings of euphoria and dependence between partners - receded over time as relationships become more established.
Loved up

Levels of the NGF protein in the 39 people (out of 58) still in the same new relationship after a year had reduced to base-line levels. Report co-author Piergluigi Politi said the study suggests that “acute love” fades over time. Looking for deeper feelings beyond the first flush of love was outside the scope of the research.

Politi said the study suggested a link between NGF and feelings of romantic love. “Our current knowledge of the neurobiology of romantic love remains scanty. But it seems from this study biochemical mechanisms could be involved in the mood changes that occur from the early stage of love to when the relationship becomes more established,” he said.

Finding of the research have been published in the Psychoneuroendocrinology journal. The Pavia team are careful to stress the need the further research. However the general thrust of their findings has received support from scientists in other disciplines.

“Research has suggested that romantic love fades after a few years and becomes companionate love and it seems certain biological factors play a role,” Dr Lance Workman, head of psychology at Bath Spa University, told the BBC. ®

Interestingly the post I made before I entitled the same thing… check it out here.

Ever wonder why men fall asleep and women want to cuddle after sex? Well if you haven’t been up with the times, research science has found the answer. Its three main chemicals: Vasopressin, Oxytocin and Serotonin. The research has come up with some interesting facts including why women want to cuddle.

When a couple has sex, the brain releases Vasopressin, Oxytocin and Serotonin. Serotonin, has a calming and relaxing effect, and mixing like a drug coctail with testosterone becomes like a sleeping pill for men, but with women who have low levels of testosterone, but higher levels of estrogen, it becomes the bonding pill, or the cuddle time. This effect is what causes women to form lasting bonds with men and in a sense causes them to become more faithful the more they get this coctail. In a sense addicted to it.

Other approaches are also shedding light on the question. In 2000, Andreas Bartels and Semir Zeki of University College, London, located the areas of the brain activated by romantic love. They took students who said they were madly in love, put them into a brain scanner, and looked at their patterns of brain activity.

The results were surprising. For a start, a relatively small area of the human brain is active in love, compared with that involved in, say, ordinary friendship. �It is fascinating to reflect�, the pair conclude, �that the face that launched a thousand ships should have done so through such a limited expanse of cortex.� The second surprise was that the brain areas active in love are different from the areas activated in other emotional states, such as fear and anger. Parts of the brain that are love-bitten include the one responsible for gut feelings, and the ones which generate the euphoria induced by drugs such as cocaine. So the brains of people deeply in love do not look like those of people experiencing strong emotions, but instead like those of people snorting coke. Love, in other words, uses the neural mechanisms that are activated during the process of addiction. �We are literally addicted to love,� Dr Young observes. Like the prairie voles.

Basically the Love emotion is like cocaine- which makes sense in a way, because if it wasnt so addictive - why would humans do it? Why would mother nature not make a way for us to find a way to continue life?

If you are interested in reading more - check it out here.