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Neural organization under hormonal versus direct-genetic effects Cynthia J. Gill, Ph.D. Asst. Professor of Physiology Ha

Neural organization under hormonal versus direct-genetic effects Cynthia J. Gill, Ph.D. Asst. Professor of Physiology Hampshire College School of Natural Sciences. Ventral medial hypothalamus (VMH). TECT. P. C. LTP. D. VE. H. V M H.

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Neural organization under hormonal versus direct-genetic effects Cynthia J. Gill, Ph.D. Asst. Professor of Physiology Ha

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

  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. Experimental procedure: testosterone estrogen females males 1 week recovery injection Gdx 6 week exposure measureER & PR mRNA expression in VMH by in situ hybridization

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

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

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

  9. Conclusions • 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 .…like brain morphology. ….like behavioral sensitivity.

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

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

  14. Conclusions II • 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. .…like brain morphology. ….like behavior.

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

  16. Sexually dimorphic Fos responses to mating stimuli

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

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

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

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