It's that time of year again, when females of many species are on the lookout for that special guy; some are even looking for their forever partner. When female prairie voles select a mate, it's a lifelong commitment, and Melissa Coleman from Claremont McKenna, Pitzer and Scripps Colleges, USA, explains that key neurotransmitters – chemicals, such as dopamine, that relay signals between nerves – are essential for lovers to bond. But, how the love story plays out depends on which receptors in the brain pick up the essential neurotransmitter signals. For example, dopamine binding to the D2 receptor, is a key process when a prairie vole female selects her Mr Forever. But, Coleman wondered how essential this particular receptor was for the chemistry between couples of other species. Knowing that female zebra finches listen for the sexiest chirrups when searching for a suitor, Coleman and a team of dedicated undergraduate researchers set about playing Cupid for courting finches to find out whether they depend on the same chemistry of attraction as prairie voles.
But first, the team needed to know how long it takes a zebra finch female to find the chirrups of a male date attractive. However, when the team offered the females a choice between the voice of a suitor that she had been housed with for a brief (24–48 h) period and that of another random male, the females were equally disinterested in both. The brief encounter had not been long enough for the courting birds to form an enduring relationship. In contrast, females that had been closeted with a male for 2 weeks were very enthusiastic when they heard their sweetheart's voice through a loud speaker. So, how would the speed-dating zebra finches feel about their date if they were given a helping hand? ‘We wondered if we could influence a female's preference for a male's song by giving female finches a drug that would specifically target D2 dopamine receptors’, says Coleman.
This time, before closeting pairs of male and female zebra finches together for 24–48 h, the team injected the females with a dopamine mimic that specifically targeted the D2 receptor in their brains, to see whether the chemistry worked better. And it did, even though they had only been together for a matter of hours. ‘It was as if they so liked that male that they wanted to find him hiding behind the speaker’, chuckles Coleman. The researchers had effectively triggered Cupid's arrow by giving the females a shot of the dopamine mimic, activating the D2 receptor in their brains.
Coleman says, ‘Dopamine acting through the D2 receptor seems to be necessary for forming song preference in female finches’. She adds, ‘This mechanism seems to be an evolutionarily conserved piece of the puzzle of how animals form social bonds’, and she is keen to learn more about the wiring that allows birds and mammals to form long-term attachments.
