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Hormones & Sexual Behavior

Hormones & Sexual Behavior. Lecture 24. Sexual Behavior of the Rat. Sex Hormones  activation Testosterone  male behavior Estrogens  female behavior estradiol Progesterone ~. Female behavior: rats. Receptive - lordosis head down haunches up Proceptive ear wiggling

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Hormones & Sexual Behavior

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  1. Hormones & Sexual Behavior Lecture 24

  2. Sexual Behavior of the Rat • Sex Hormones  activation • Testosterone  male behavior • Estrogens  female behavior • estradiol • Progesterone ~

  3. Female behavior: rats • Receptive - lordosis • head down • haunches up • Proceptive • ear wiggling • darting • Hopping ~

  4. Male behavior: rats • Mounts • no testosterone  no mounting • Intromits several times • Ejaculates • 4-5 times • 5 min refractory period ~

  5. Organizational Effects of Hormones • SDN & SNB • Critical periods • Humans - prenatal • Rats - perinatal • easily manipulated ~

  6. Hormones: Sexual Behavior • Castrate XY males at birth • Later... • testosterone  no male behavior • estrogen? • lordosis • Brain not masculinized ~

  7. Hormones: Sexual Behavior • Ovariectomize female at birth • give testosterone • Later... • estrogens  no female behavior • testosterone  male behavior • Brain masculinized ~

  8. Human Sexual Behavior • No stereotypical M & F behaviors • Men are like rats • T plays a activational role • Castration • decline in sexual behaviors • variable rate • Role of oxytocin? • probably not • knockout mice ~

  9. Hormones - Women • Estrogen & Progesterone • no activational effects • Ovariectomy has no effect • Some fx on willingness to copulate • increased during ovulation • E & P are high ~

  10. Hormones - Women • Testosterone levels • correlated with frequency of intercourse • Oxytocin • uterine and vaginal contractions • sensations associated with orgasm ~

  11. Brain Mechanisms: Rats • Medial preoptic area • lesion SDN  no M sexual behavior • NOT sexual motivation • Bar press for female ~

  12. Brain Mechanisms: Rats • Ventromedial nucleus • lesion- no female sexual behavior • Masculinizes by preventing cell death • Amygdala • lesion  increased sexual behavior • Indiscriminate ~

  13. Homosexuality • Sex hormones role? • rats - yes • Humans? • NOT SURE • Learning experiences? • or biologically determined? ~

  14. Biological Factors • Levels of circulating sex hormones? • No • Differences in brain structure? • Perhaps - Where? ~

  15. Homosexuality • Simon LeVay • Brains of male AIDS victims • Anterior Hypothalamus • Anterior commissure • SDN (rats) • Humans: 3rd interstitial nucleus ~

  16. 3d interstitial nucleus • Anterior commissure larger in females • Similar relationship ~ .15 .10 .05 Volume mm3 F H-M M

  17. Homosexuality 2 Hypotheses 1. Androgen levels • low in XY fetuses that  gay • high in XX fetuses  lesbian 2. Genetic differences in fetal brains response to androgens • Xq28- tip of the X chromosome • shared by large % of gay brothers ~

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