Hormones--Cell Survival:
Ex. Sexually Dimorphic Nucleus of the Preoptic Area (SDN-POA) (in rats)
SDN-POA is 3-5 times larger in males than in females
aromatization of testosterone to estrogen is important for masculinization
originally thought--androgens were important in stimulating the number of neurons born in males that will migrate to, and form, the SDN-POA (book)
however--more recent data suggest that exposure to androgens perinatally act to increase the number of neurons that survive in males than in females
how can we follow cell birth/survival? tritiated thymidine autoradiography
current view: (following injection of 3H-thymidine on day 18 of gestation)
- PN4--# neurons in SDN-POA: males=androgenized females= females
- PN7--# neurons in SDN-POA: [males=androgenized females]>females
- neurons are lost in females at PN7 and PN10; exposure to testosterone (from E20 to PN10) can prevent this loss
- males have larger SDN-POA because more neurons survive into adulthood, and also because of an increase in volume not associated with addition of more neurons--increase in cell size (larger) and/or more connections
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