by Jayashree on  August 6, 2007 at 1:37 PM Research News
Women Act Like Men at Just a Tweak of the Nose
London, Aug 6 (ANI): A small sensory organ found in the noses of all terrestrial vertebrates except higher primates seems to be the epicenter of sex-specific conduct in these species according to a new study.

The researchers believe that earlier assumption, that these differences arise in the brain, may be unfounded.

"These results are flabbergasting. Nobody had imagined that a simple mutation like this could induce females to behave so thoroughly like males," Nature quoted says Catherine Dulac, Higgins Professor of Molecular and Cellular Biology in Harvard's Faculty of Arts and Sciences and an investigator with the Howard Hughes Medical Institute, as saying.

However, the results do not apply directly to humans because of the absence of the vomeronasal organ.

Yet, the study may offer pathways to understand sex-specific human behaviour.

Dulac and co-authors Tali Kimchi and Jennings Xu analyzed female mice alternation in TRPC2, an ion channel, which works with the nose to detect pheromones.

The absence of the ion channel disables the organ.

They discovered that females indulge in male courtship activity, when they are kept with a sexually experienced male in the same cage. They also showed male sexual behaviour.

After giving birth, these females were found to lack maternal behaviour as they wander away from their newborns and eventually abandon them.

"There are two possible interpretations. Either the vomeronasal organ may be needed to grow a female-specific neural circuit during development, or the mature female mouse brain may require vomeronasal activity to repress male behaviour," Dulac said.

To test the alternatives, Dulac and her colleagues cut out the vomeronasal organs from the nasal septa of normal adult females. These began exhibiting male behaviours, though they showed testosterone levels, oestrogen levels, and oestrus cycles indistinguishable, that is found in normal females.

"It had previously been thought that entirely different neural circuits, modulated by these hormones, controlled sex-specific behaviour. Remarkably, our work suggests that neuronal circuits underlying male-specific behaviours develop and persist in the female mouse brain, but are repressed by the normal activity of the vomeronasal organ," Dulac said.

"In fact, our research suggests a new model where exactly the same neural circuitry exists in males and females. In this model, only the vomeronasal pathway itself -- which serves as a switch that represses male behavior while promoting female behavior -- is dimorphic. While male and female bodies are strikingly different physiologically, it appears the same cannot be said for the brain," Dulac said.

Dulac and colleagues are now trying to understand the behaviour of male mice mutant for TRPC2 to see if they display female-like characteristics.

The study is published in this week's Nature.

Source: ANI

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