Testosterone directly amplifies but does not program male behaviors

Apr 28, 2010

New research uncovers some surprising information about how sex hormones control masculinization of the brain during development and drive gender related behaviors in adult males. The study, published by Cell Press in the April 29 issue of the journal Neuron, demonstrates that direct action of testosterone, the prototypical male hormone, is unnecessary for masculinizing the brain and behavior.

Testosterone and estrogen are thought to play an essential role in organizing and activating gender-specific patterns of behavior in sexually reproducing animals. is produced by the testes and directly activates the (AR) in target tissues such as muscle. Estrogen is produced by the ovaries and is nearly undetectable in the circulation of males of most species. However, circulating testosterone in males can be converted into estrogen in the brain, and this testosterone-derived estrogen has been shown to control many male behaviors.

"It was known that testosterone and estrogen are essential for typical male behaviors in many vertebrate species," explains the study's senior author, Dr. Nirao M. Shah from the Department of Anatomy at the University of California, San Francisco. "However, how these two hormones interact to control masculinization of the brain and behavior remained to be established."

Dr. Shah and colleagues found that during the neonatal testosterone surge there is very little AR expressed in the developing brain, making it unlikely that testosterone signaling via AR plays a major role in masculinizing neural pathways. Importantly, they went on to show that the male pattern of AR expression in the brain was dependent on testosterone-derived estrogen signaling.

The researchers then used a genetic approach to knock out the AR in the mouse and observed that these mutants still exhibited male type mating, fighting, and territorial marking behaviors. However, these mutant males had striking reductions in specific components of these masculine behaviors. These results show that testosterone signaling via AR does not control masculine differentiation of the brain and behavior but regulates the frequency and extent of male typical behaviors.

"Our findings in conjunction with previous work suggest a model for the control of male pattern behaviors in which estrogen masculinizes the neural circuits for mating, fighting, and territory marking, and testosterone and signaling generate the male typical levels of these behaviors," concludes Dr. Shah. "It will be interesting in future studies to identify the molecular and circuit level mechanisms that are controlled by these hormones."

Explore further: Omega-3 fatty acids and vitamin D may control brain serotonin

More information: Juntti et al.: “The Androgen Receptor Governs Execution, but Not Programming, of Male Sexual and Territorial Behaviors.” Publishing in Neuron 66, 260-272, April 29, 2010. DOI:10.1016/j.neuron.2010.03.024

Related Stories

The making of the male brain (estrogen required)

Oct 01, 2009

Territorial behavior in male mice might be linked to more "girl-power" than ever suspected, according to new findings at UCSF. For the first time, researchers have identified networks of nerve cells in the brain that are ...

Androgen therapy may slow progress of Alzheimer's disease

Dec 20, 2006

Experiments on mouse models of Alzheimer's disease (AD) suggest that treatment with male sex hormones might slow its progression. The findings, published in the December 20 issue of The Journal of Neuroscience, provide new in ...

Recommended for you

Omega-3 fatty acids and vitamin D may control brain serotonin

3 hours ago

Although essential marine omega-3 fatty acids and vitamin D have been shown to improve cognitive function and behavior in the context of certain brain disorders, the underlying mechanism has been unclear. In a new paper published ...

Researchers develop method for mapping neuron clusters

6 hours ago

A team of scientists has developed a method for identifying clusters of neurons that work in concert to guide the behavior. Their findings, which appear in the journal Neuron, address a long-standing mystery about the or ...

One brain area, two planning strategies

10 hours ago

Ready to strike, the spear fisherman holds his spear above the water surface. He aims at the fish. But he is misled by the view: Due to the refraction of light on the surface, he does not see the actual location ...

Study maps extroversion types in the brain's anatomy

17 hours ago

Everyday experience and psychological studies alike tell us that there are two different types of extroverts: The gregarious "people-persons" who find reward in sharing affection and affiliation with others, ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.