Writers of novels and songs have for centuries claimed that love is  drug. Scientists have now gone  step further to prove this assertion. They conducted tests on  romantic relationships among prairie voles. Different pairs of  mouse-like rodents were tested for levels of dopamine -  neurotransmitter that plays  role in our seeking pleasure and  craving for addictive things. It can provide  intense feeling of reward. The researchers found that  voles released large amounts of dopamine when they were physically with their "established partner". Researcher Dr Zoe Donaldson said parts of  voles' brains lit up "like  glow stick" when they were reunited with their mates, and dimmed when with unknown voles.
The researchers said their studies help to explain much about  complexities of human relationships. They say dopamine in our brains plays  key part when falling in love, and in  grief experienced when breaking up with  partner. Dr Donaldson said: "As humans, our entire social world is basically defined by different degrees of selective desire to interact with different people, whether it's your romantic partner or your close friends." She added: "This research suggests that certain people leave  unique chemical imprint on our brain that drives us to maintain these bonds over time." Research also suggests that women get over  breakup, and fall out of love faster than men.