Happily ever after? It's all in your head

ATLANTA, Georgia (CNN) -- Is there such a thing as everlasting love?

VIDEO CNN's Elina Fuhrmann reports certain chemicals in the brain may be associated with the success or failure of love relationships (February 14) Play video (QuickTime, Real or Windows Media)

That all depends on your definition, scientists say. The passion that swells at the beginning of a relationship is actually transitory, dependent on a cocktail of chemicals that act on the brain.

But other compounds also act to make love last.

Scientists at Emory University in Atlanta were able to make mouse-like animals called voles monogamous, by injecting them with certain chemicals.

CNN's Elina Fuhrman has details.