In male fetal brain aromatase convert testosterone into estrogen which induces the masculinization of the brain. Thus, it is likely that by inhibition of aromatase the masculinization of male fetal brain will be blocked.In the present research the effect of maternal administration of aromatase inhibitor (letrozole) during the critical period of brain sexual differentiation on spatial memory of male offspring is studied. Pregnant Wistar rats were administered letrozole (0.5mg/kg) at19th and 20th days of pregnancy. When offspring were become 2 months old, the spatial memory of experimental male offspring were compared by age-matched male and female controls, using Morris water maze. In compare with male and female controls, the mean time to reach the platform on days 1-4, as a criteria for learning, and the mean time spent in target quadrant on day 5 (probe test) in experimental males were between the control male and female. These finding may indicate that the process of masculinization of the brain of male offspring has not been done completely.

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