Lotharios tamed by brain protein

HELEN R. PILCHER

Prairie voles (top) like to huddle, unlike solitary meadow voles. © M. Lim

Want to tame the eye of a philandering love rat? Then help is at hand. New research shows that gene therapy can turn promiscuous male voles into faithful bedfellows.

Miranda Lim from Emory University in Atlanta, Georgia, and colleagues used a virus to introduce a gene directly into the brain of male meadow voles (Microtus pennsylvanicus). The gene encodes a protein called the vasopressin receptor, which helps to regulate social behaviour and pair bonding.

A few days later, the normally promiscuous rodents developed high levels of vasopressin receptors and lost their lust for the ladies. The results are reported in this week's Nature¹.

The animals' brain chemistry and behaviour resembles that of their relative, the monogamous prairie vole (Microtus ochrogaster). These faithful creatures mate for life and have many vasopressin receptors in the ventral forebrain, a brain region known to regulate addiction and reward.

Increasing the number of vasopressin receptors in this area gives an animal a sense of reward when it forms a close pair bond, explains Lim. So lecherous animals calm their errant ways.

"It's amazing to think that altering just one gene can regulate such a complex behaviour," says Lim.

Vole love

Lim's team paired male prairie and meadow voles with a sexually receptive female of the right species. Each pair was allowed a day to get to know each other, then the males were given a fidelity test.

Each vole was allowed to wander freely between his tethered partner and a tethered stranger. Prairie voles and genetically modified meadow voles huddled close to their partner; untreated meadow voles preferred to spend time alone.

Earlier work has shown that boosting vasopressin receptor levels speeds up pair bond formation in monogamous voles. The new research shows that a similar technique can turn a promiscuous species of vole into a faithful one.

This has implications for species evolution. "The study suggests that promiscuous species may harbour the potential to engage in pair bond formation," says Lim.

Whether or not the technique could work in humans is not known. Promiscuous and monogamous monkey species have different patterns of vasopressin receptor expression that closely match those seen in the voles. So it is possible that philandering and faithful humans may share similar brain chemistry, says Lim.

But pair bonding in humans is more complex, cautions psychologist Evan Balaban from McGill University, Montreal, Canada. Social factors, economics, history and individual differences all play a role.

1. Lim, M. M. et al. Nature, 429, 754 - 757, doi:10.1038/nature02539 (2004). |Article|

© Nature News Service / Macmillan Magazines Ltd 2004