Female hormone drives male aggression in mice

October 3rd, 2009 - 2:30 pm ICT by IANS  

Washington, Oct 3 (IANS) The female hormone oestrogen seems to drive male aggression in mice with the help of certain nerve cells in the brain, a new study led by an Indian American has found.
The study, conducted by University of California San Francisco (UCSF), suggests a pivotal role for oestrogen — as well as the enzyme aromatase that is responsible for oestrogen synthesis — in male territorial behaviour.

Oestrogen’s role in the mating behaviours of these mice, however, was less clear, which indicates that territorial and sexual behaviours are likely influenced by distinct and separate connections in the brain, according to Nirao Shah, assistant professor of anatomy at the UCSF and senior study author.

“This really changes the way we view male and female behaviours,” said Shah, who also is affiliated with the UCSF programs in neuroscience.

“What we previously looked upon as a single unit of gender-related behaviour, we now see as a collection of separate behaviours controlled at least in part by distinct neural pathways.”

Males and females across all sexually reproducing species display gender-specific behaviour in many areas, including mating, territorial marking, aggression and parental care, Shah explained.

Collections of cells form circuits in the brain, referred to as neural pathways, that control these and other behaviours. Shah said that both oestrogen and the male hormone testosterone are known to be essential in developing these circuits and in sex-specific behaviour.

But the precise role of these hormones and how they may interact genetically to control these behaviours has been unclear, says an UCSF release.

The current study fills in at least one piece of the puzzle, he said. The study suggests that the conversion of testosterone in the brain to oestrogen by the enzyme aromatase is critical to developing and activating brain circuits that control male territorial behaviour.

These findings were published in the journal Cell.

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