Aug. 29, 2005 Gender politics aside, every biologist knows that men and women truly are different.
Social disorders such as autism constitute one area where those differences come to the fore: around 80 percent of all autism cases, for example, occur in men. Social play behaviors also differ greatly between the sexes—just about everyone agrees that young boys play "rougher" than girls.
Early in human development, critical brain proteins known as steroid receptors lay most of the groundwork for ensuing sexual destinies. The receptors bind to hormones such as testosterone and estrogen and set in motion gender blueprints for a lifetime.
To understand why autistic children have trouble engaging in social interactions, researchers have long observed "rough-and-tumble" play—the propensity to bite, wrestle or pounce—in juvenile rats. Scientists were convinced that testosterone solely dictated the onset of such behavior.
But researchers at UW-Madison have now made the surprising finding that estrogen-and even dopamine, a neurotransmitter-also play critical roles. The work, which appeared online Aug. 16 in the journal Endocrinology, may one day help diagnose new autism cases and potentially pave the way for new hormone-based therapeutic approaches that counteract the social difficulties of autism, says senior author Anthony Auger, an assistant professor of psychology.
"Our work points out an overlooked mechanism that controls social play behavior," says Auger. "Now if we work to understand how these biological mechanisms control social behavior, we can discern which points of the various pathways are involved in the disruption of social interactions."
Male rats are likely to engage in rough-and-tumble play almost 13 times as frequently as females, says Auger. But when the UW-Madison team treated newborn females with estrogen, they bit, boxed, pinned and pounced as frequently as the males after reaching juvenile age. The estrogen effectively "masculinized" the females, Auger says.
To the scientists' surprise, a similar result took place when they treated the females with a mimic of the neurotransmitter dopamine, a chemical messenger in the brain that regulates emotions and feelings of pleasure.
The UW-Madison study results imply that many factors, beyond steroid receptors and sex hormones, may be interrupted during the onset of social disorders, Auger says. Consequently, he hopes to focus on the potential role of another group of proteins - known as growth factors - in social play behaviors.
Other scientists who participated in the study include UW-Madison doctoral student and lead author Kristin Olesen, zoologist Catherine Auger and research specialist Heather Jessen.
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