July 19, 2004

Young: Gene holds key to vole monogamy


By Poul Olson

Researchers at the Yerkes National Primate Research Center and the Center for Behavioral Neuroscience (CBN) have found that transferring a single gene, the vasopressin receptor, into the brain's reward center makes a promiscuous male meadow vole monogamous.

This finding, which appeared in the June 17 issue of Nature and drew national media attention, may help better explain the neurobiology of romantic love, as well as disorders (such as autism) of the ability to form social bonds. In addition, the finding supports previous research linking social bond formation with drug addiction, also associated with the reward center of the brain.

In their study, Yerkes and CBN postdoctoral fellow Miranda Lim and Yerkes researcher Larry Young of psychiatry and behavioral sciences, tried to determine whether differences in vasopressin receptor levels between prairie and meadow voles could explain their opposite mating behaviors. Previous studies of monogamous male prairie voles, which form lifelong social or pair bonds with a single mate, determined the animals' brains contain high levels of vasopressin receptors in one of the brain's principal reward regions, the ventral pallidum. The comparative species of vole, the promiscuous meadow vole, which frequently mates with multiple partners, lacks vasopressin receptors in the ventral pallidum.

The scientists used a harmless virus to transfer the vasopressin receptor gene from prairie voles into the ventral pallidum of meadow voles, which increased vasopressin receptors in the meadow vole to prairie-like levels. The researchers discovered, just like prairie voles, the formerly promiscuous meadow voles then displayed a strong preference for their current partners rather than new females.

Young acknowledged many genes are likely involved in regulating lifelong pair bonds between humans. "Our study, however, provides evidence in a comparatively simple animal model that changes in the activity of a single gene can profoundly change a fundamental social behavior of animals within a species," he said.

According to previous research, vasopressin receptors also may play a role in disorders of the ability to form social bonds, such as the trait displayed by some autistics. "It is intriguing," Young said, "to consider that individual differences in vasopressin receptors in humans might play a role in how differently people form relationships."

And, Lim added, past research in humans has shown the same neural pathways involved in the formation of romantic relationships are involved in drug addiction. "The brain process of bonding with one's partner may be similar to becoming addicted to drugs; both activate reward circuits in the brain," Lim said.

The researchers' next step is to determine why there is extensive variability in behaviors among individuals within a species. This could help further understanding of the evolution of social behavior.