ABSTRACT
I. Introduction................................................................................. 344 II. Sex Differences in Brain and Behavior ..................................... 344
A. Reproductive Behavior ......................................................... 345 B. The Medial Preoptic Area ..................................................... 345 C. Role of Perinatal Gonadal Hormones in Sexual
Differentiation........................................................................ 345 1. Testosterone during Development .................................. 346 2. Nuclear Steroid Receptors in Developing Brain............ 346 3. Steroid Hormones and Sexual Differentiation of
Brain and Behavior .......................................................... 346 a. Rodent Models ............................................................ 346 b. Sex Differences in Human Brain and Behavior ........ 348
D. Summary ................................................................................ 349 III. Progesterone and the Developing Brain ................................... 349
A. Evidence for Perinatal Exposure to Maternal Progesterone .......................................................................... 349 1. Relationship between Maternal and Fetal
Progesterone Levels ......................................................... 349 2. Neonatal Progesterone Exposure during Lactation? ..... 350
B. Progesterone Receptors in Developing Brain ..................... 350 1. Sex Differences in Expression ......................................... 351
C. Summary ................................................................................ 352 IV. Effects of Perinatal Exposure to Progesterone ......................... 352
A. Rodent Models....................................................................... 352 1. Behavioral Effects ............................................................. 352 2. Neural Effects ................................................................... 353
B. Progestin Treatment in Human Pregnancy ......................... 355 C. Closing Remarks.................................................................... 355
V. Acknowledgments ...................................................................... 355 References ............................................................................................. 355
Between the two sexes of almost all mammalian species are differences in both the quality and quantity of specific behaviors. It is widely accepted, at least with regard to many rodent models, that sex differences in neural structure, chemistry, and function underlie these behavioral dimorphisms. There is an enormous literature to support the idea that exposure to steroid hormones during particular periods of fetal and/or neonatal development, specifically hormones of fetal testicular origin, set the course for masculinization of the central nervous system (CNS).
