Neurological effects of aromatase deficiency in the mouse.

[aromatase deficiency]

In the brain , the conversion from androgen into estrogen is an important process for the differentiation of the brain function in male rodents . The aromatase is expressed in some nucleus of the brain . To assess the functional significance of the aromatase gene in development and activation of sex-specific behavior , we analyzed behavioral phenotypes of the aromatase knockout (ArKO ) male mice . ArKO males obviously decreased their fertility and showed deficits in male sexual behavior including mount , intromission and ejaculation . Noncontact penile erection was not significantly affected by defect of the aromatase gene . A reduction of aggressive behavior against male intruders was also observed in ArKO males , while they tend to exhibit aggression toward estrous females during male copulatory tests . Moreover , the infanticide toward the pups was observed in the ArKO males , whereas characteristic parental behavior , but not infanticide was observed in wild-type males . These results indicate that aromatase gene expression is a critical step not only for motivational and consummatory aspects of male sexual behavior , but also for aggressive and parental behaviors in male mice .