1. Neural organization under hormonal versus direct-genetic effects Cynthia J. Gill, Ph.D. Asst. Professor of Physiology Hampshire College School of Natural Sciences

2. essential brain area controlling female-typical sexual behavior sexually dimorphic in adult male and female whiptails site of estrogen sensitivity Ventral medial hypothalamus (VMH) PC V M H D H LTP VE TECT

3. / +E/ +E / +E / +E Injection blank(/) or estrogen (+E)

4. Question Since adult males have higher testosterone levels than adult females... is chronic testosterone exposure responsible for the steroid receptor expression differences observed between adult males and females?

5. testosteroneestrogen males females 6 week exposure 1 week recovery injection Experimental procedure: measure ER & PR mRNA expression in VMH by in situ hybridization Gdx

6. SSV SSV + estrodiol benzoate SSV + estrodiol benzoate (high magnification)

7. 0 15 5 10 25 20 30 Mean in situ grains/cluster (+SEM) Progesterone receptor mRNA expression in the adult VMH T/- T/E -/E T/- -/E -/- 6 week exposure/injection Modified from Wennstrom, Gill and Crews, 1998 aa b a b c

8. 0 15 5 10 25 20 30 Mean in situ grains/cluster (+SEM) Estrogen receptor mRNA expression in the adult VMH T/- T/E -/E T/- -/E -/- 6 week exposure/injection a b b Gill, Crews & Wennstrom, 2004

9. Estrogen-induced progesterone receptor mRNA is fixed in an adult female, but responsive to testosterone environment in an adult male Estrogen-induced estrogen receptor mRNA is fixed in an adult male, but responsive to testosterone environment in an adult female Conclusions ….like behavioral sensitivity..…like brain morphology.

10. Testosterone... directly regulates expression of some genes can be converted to estrogen by aromatization to regulate other genes affects synaptic connectivity affects the size of cells affects cell survival

11. E PR - POA VMH Male +T Male, no T Female E PR cell death Model: Variation in cell survival early and cell connectivity later

12. Question Since adult males and females differ in hormone receptor induction... is the sensitivity the result of hormonal or direct-genetic effects during development?

13. Sexual, parthenogenic and sex-reversed whiptails C. inornatus C. costatus or C. burti C. uniparens F 1 parthenoform X X C. uniparens - created by blocking estrogen production in the embryo C. inornatus Sexual & Parthenogen & (‘male’ is genetically female, hormonally male)

16. Estrogen-induced progesterone receptor mRNA expression is not sexually dimorphic at one and thirty days of age Estrogen-induced estrogen receptor mRNA is sexually dimorphic at one and thirty days of age The sex dimorphism in estrogen receptor mRNA expression is reversed in very young animals and it is hormone dependant. Conclusions II.…like brain morphology. ….like behavior.

17. Undergraduate research assistants: Michelle Embleton Molly Fant Jen Lui Kavita Juneja Laura Young Drs. David Crews and Kira Wennstrom Acknowledgements

20. Sexually dimorphic Fos responses to mating stimuli

21. Female response to chemosensory cues and mating Male response to chemosensory cues and mating

22. Mean in situ grains/cluster (+SEM) Progesterone receptor mRNA expression in the adult VMH T/- T/E -/E -/- -/E T/- -/E -/- T/- T/E a a a b b c

23. Mean in situ grains/cluster (+SEM) Estrogen receptor mRNA expression in the adult VMH T/- T/E -/E -/- -/E T/- -/E -/- T/- T/E b a b