 MeCP2 in the developing rat brain regulates important social development in a sexually dimorphic manner.MeCP2 levels are different between males and females in the developing rat brain 24 hours after birth within the amygdala and hypothalamus, but this difference is no longer observed 10 days after birth.Specifically, males express less MeCP2 than females, and this aligns with the steroid-sensitive time period of the neonatal rat brain.