Sometimes, the expectations of a proud father from his son are at the mercy of brain chemicals.

Researchers from University of Illinois, Chicago have found that the ability of making the difference between sexes is due to receptors on the surface of neurons and their number is determined by a common brain compound, whose precise role was unknown till these experiments on fruit flies.

Neuronal receptors dictate every activity of the nerve cells: from learning to the transmission of information and from debilitating illnesses (like sclerosis, muscular dystrophy, post-traumatic stress syndrome) to schizophrenia.

A high number of receptors at the synapses means better transmission of the information.

The research team found this number is determined by glutamate; however, not the one from the synapses, but ambient extracellular glutamate, which just hangs around the neurons and whose role was till now not known. "People figured you couldn't use glutamate to send messages because there was too much glutamate background noise in the brain. It turns out that this background noise plays an important part in regulating information transfer" said David Featherstone, assistant professor of biological sciences.

The glia cells, which along with the neurons fill the brain, were found to be the source of the ambient glutamate. The team found transporter proteins - named xCT - that regulate the level of extracellular glutamate by pumping it out from glia cells. "When we mutate the protein, we get less ambient extracellular glutamate, more glutamate receptors, and so a stronger transfer of messages at synapses," Featherstone said.

This mutation, named "genderblind", rendered the flies bisexual. "The mutants are completely bisexual, but fertile. It's the first gene that really specifically affects homosexual behavior without affecting heterosexual behavior," he said.

"Trying to understand fly bisexuality sounds silly, but these behavioral changes are important evidence that ambient extracellular glutamate and xCT transport proteins play important, unsuspected roles in brain function," Featherstone said.

"We think we'll be able to learn a lot about perception and development from figuring out exactly what's happening in these flies."

"It's amazing how many biomedical breakthroughs have come from crazy directions."