1. Copyright © Allyn & Bacon 2010 Reproductive Behavior Chapter 10

2. Lecture Preview  Sexual Development  Hormonal Control of Sexual Behavior  Neural Control of Sexual Behavior  Parental Behavior

3. Sexually Dimorphic Behaviors Behavior that has different forms or that occurs with different probabilities or under different circumstances in males and females. ▫Courting ▫Mating ▫Parental behavior ▫Most forms of aggressive behaviors Hormones present before and after birth – development and control of SDBs

4. Figure 10.1 Determination of Gender Male testes produce sperm cells Female ovaries produce ova Sperm and ova each have 23 chromosomes Fertilization Sperm cell + ovum = zygote 23 pairs of chromosomes X and Y – sex chromosomes XX = female, XY = male

5. Development of the Sex Organs 3 general categories of sex organs: Gonads ▫Testes or ovaries Internal sex organs ▫Fimbriae and fallopian tubes, uterus, inner 2/3rds of the vagina ▫Epididymis, vas deferens, seminal vesicles External sex organs ▫Penis and scrotum ▫Labia, clitoris, outer part of vagina

6. Hormones & Sexual Development Gonads Function: produce ova or sperm and secrete hormones Initially there is a primordial gonad (6 weeks) ▫Cortex – potential to be an ovary ▫Medulla – potential to be a testis

7. Sexual Development Gonads Copyright © 2009 by Allyn & Bacon Six weeks post-conception… ▫Y chromosome Sry gene makes Sry protein which triggers development of primordial gonad medulla into testis ▫If no Y chromosome, then ovaries develop

8. Sexual Development  Organizational Effects – hormonal effects on tissue differentiation and development  Influence the development of a person’s sex organs and brain  Effects are permanent  Activational Effect – effect of a hormone that occurs in the fully developed organism.  Occur after sex organs have developed

9. Sexual Development Internal Reproductive Ducts Both sexes begin with two sets of reproductive ducts ▫Wolffian system – male – Epididymis, vas deferens, seminal vesicles ▫Müllerian system – female – Fimbriae and fallopian tubes, uterus, inner 2/3rds of the vagina The gender of the internal sex organs is determined by the presence or absence of hormones secreted by the testes

10. Sexual Development Internal Reproductive Ducts Third prenatal month: differentiation of ducts ▫Testes produce androgens (maculinizing) and anti-Müllerian hormone (defeminizing)  Wolffian system develops, M ü llerian degenerates, testes descend ▫No testes – no testicular hormones  M ü llerian system develops, Wolffian degenerates Ovaries are almost completely inactive during fetal development ▫Development of the Müllerian system occurs in any fetus that is not exposed to testicular hormones during the critical fetal period

11. Sexual Development  Wolffian System – embryonic precursors of the male internal sex organs.  Anti-Mullerian Hormone – peptide secreted by fetal testes that inhibits the Mullerian system.  Androgens – male sex steroid hormone (e.g., testosterone).  Dihydrotestosterone – androgen produced from testosterone.

12. Sexual Development External Reproductive Organs Genitalia – develop from one bipotential precursor Differentiation occurs in second month ▫Androgens produces male structures ▫Without testosterone, female structures develop ▫Males – penis and scrotum ▫Females – labia, clitoris, outer part of vagina

13. The development of male and female external reproductive organs from the same bipotential precursor Copyright © 2009 by Allyn & Bacon Sexual Development

14. Default is female!

15. Androgenic Insensitivity Syndrome Mutation in the androgen receptor gene – androgen receptors totally unresponsive During development(XY), testes release normal amounts of androgens for a male, but androgen receptors are mutated ▫Development proceeds as if no androgens are released  Lack of masculinizing effect - epididymis, vas deferens, seminal vesicles, and prostate fail to develop During development, testes release normal amounts of anti- Mullerian hormone ▫Defeminizing effect – preventing the female interal sex organs from developing  Uterus, fimbriae, Fallopian tubes fail to develop, vagina is shallow ▫External genitalia is female, at puberty the person develops a women’s body

16. Persistent Mullerian duct syndrome 2 causes ▫Failure to produce anti-Mullerian hormone ▫Absence of receptors for anti-Mullerian hormone In genetic males (XY), androgens have their masculinizing effect but defeminization does not occur Person is born with both sets of internal sex organs Presence of additional female sex organs usually interferes with normal functioning of the male sex organs.

17. Turner’s syndrome 1 sex chromosome: X ▫Most cases X comes from mom, defective sperm No testes – no Y chromosome No ovaries - 2 X chromosomes are needed to produce ovaries Develop female with normal female internal sex organs and external genitalia Fetuses do not need ovaries or the hormones they produce to develop as female Given estrogen pills to induce puberty and sexual maturation No children

18. Default is female!

19. FIGURE 10.5 HORMONAL CONTROL OF DEVELOPMENT

20. Sexual Development  Sexual Maturation ▫ Onset of puberty occurs when cells in hypothalamus secrete gonadotropin-releasing hormones (GnRH)  Under control of kisspeptin  Produced by neurons in the arcuate nucleus (hypothalamus) ▫ Essential for initiation of puberty and maintenance of male and female reproductive ability ▫ Stimulate the production and release of 2 gonadotropic hormones from the anterior pituitary gland  Follicle-stimulating hormone (FSH)  Luteinizing hormone (LH) ▫ Gonadotropic hormones stimulate the gonads to produce their hormones, which is responsible for sexual maturation

21. Sexual Maturation In response to gonadotropins, the gonads secrete steroid sex hormones ▫Ovaries produce estradiol  Estrogens ▫Testes produce androgens  testosterone Both glands produce a small amount of the other hormone

22. Sexual Maturation Estadiol in females ▫Breast development, growth in lining of uterus, changes in deposition of body fat, maturation of female genitalia Androgens in males ▫Stimulate growth of facial, underarm, and pubic hair, lower the voice, alter hairline on head, stimulate muscular development, genital growth Table 10.1

23. Sexual Maturation Age at which children (girls) reach puberty has been decreasing Improved nutrition ▫Thin girls reach puberty later than obese girls Leptin ▫Plays a role in determining the onset of puberty in females ▫Receptors located on kisspeptin-secreting neurons in ArcN

24. Lecture Preview  Sexual Development  Hormonal Control of Sexual Behavior  Neural Control of Sexual Behavior  Parental Behavior

25. Hormonal Control of Sexual Behavior Menstrual cycles vs. estrous cycles ▫Growth and loss of uterus lining ▫Mating behavior (estrous cycle – limited sex) Cycle begins with secretion of gonadotropins by anterior pituitary gland FSH – stimulate growth of ovarian follicles ▫As ovarian follicles mature, they secrete estradiol, causes growth of lining (preparation for implantation of ovum if fertilized) Feedback from increased estradiol triggers release of LH LH causes ovulation, follicle ruptures and releases ovum LH – ruptured follicle becomes a corpus luteum which produces estradiol and progesterone Progesterone – promotes pregnancy ▫Maintains lining of uterus, inhibits ovaries from producing additional follicles If ovum is not fertilized or fertilized late, corpus luteum stops producing estradiol and progesterone, lining will slough off

26. Hormonal Control of Sexual Behavior in Lab Animals  Males  Sexual Behavior  Intromission – entry of penis into the female’s vagina  Pelvic Thrusting  Ejaculation – discharge of semen  Refractory Period  Coolidge Effect – restorative effect of introducing a new female sex partner to a male that has apparently become exhausted by sexual activity.

27. Hormonal Control of Sexual Behavior in Lab Animals Males ▫Depends on testosterone (T)  If male is castrated, sexually activity stops  Can be reinstated by injections of T ▫Oxytocin – hormone produced by posterior pituitary gland  Causes milk ejection in lactating females  Released during organism in males and females  Role in pair bonding

28. Hormonal Control of Sexual Behavior in Lab Animals Females – if receptive  Lordosis  Approach males, nuzzle, hoping, ear wiggling ▫Depends on gonadal hormones present during estrus  Estradiol and progesterone ▫Estradiol increases about 40 hrs before the female becomes receptive  Ovariectomized rats can become sexually receptive with injections of estradiol and progesterone  Female mice without estrogen receptors (or progesterone receptors) were unreceptive to males even after estradiol and progesterone

29. Hormonal Control of Sexual Behavior in Lab Animals Sequence of estradiol followed by progesterone has 3 effects on female rats 1.Receptivity – ability and willingness to copulate 2.Proceptivity – eagerness to copulate 3.Attractiveness – physiological and behavioral changes that affect the male 1.Odor and her behavior

30. Organizational Effects of Androgens on Behavior: Masculinization and Defeminization Female is default! If a rodent’s brain is not exposed to androgens during a critical period of development, the animal will engage in female sexual behavior as an adult (if given E and P) Critical period in rats is shortly after birth If a male rat is castrated immediately after birth, as an adult (given E and P), the male rat will display lordosis in the presence of another male

31. Organizational Effects of Androgens on Behavior: Masculinization and Defeminization If rodent brain is exposed to androgens during development: ▫ Behavioral Defeminization – organizational effect of androgens that prevents the animal from displaying female sexual behavior in adulthood  If a female rat is OVX and injected with T immediately after birth, she will not respond to a male rat when (as an adult) she is given E and P ▫ Behavioral Masculinization – organizational effect of androgens that enables animals to engage male sexual behavior in adulthood  If female rat is OVX and injected with T immediately after birth, and given T in adulthood, she will mount and attempt to copulate with a receptive female

32. Hormonal Control of Sexual Behavior  Effects of Pheromones ▫ Chemical released by one animal that affects the behavior or physiology of another. ▫ Lee-Boot Effect – slowing and eventual cessation of estrous cycles in groups of female animals housed together ▫ Whitten Effect – synchronization of the menstrual or estrous cycles of a group of females occurs only in the presence of a pheromone in a male’s urine. ▫ Vandenbergh Effect – earlier onset of puberty seen in female animals that are housed with males, caused by pheromone in male’s urine. ▫ Bruce Effect – termination of pregnancy caused by the odor of pheromone in a male’s urine, other than the one that impregnated the female.

33. Effects of Pheromones Detection of odors is accomplished by the olfactory bulbs Some of the effects of pheromones act on the Vomeronasal organ (VNO) VNO ▫Small group of sensory receptors connected by a duct to the nasal passage ▫Projects to accessory olfactory bulb (AOB), behind the olfactory bulb Removal of AOB disrupts the Lee-Boot effect, the Whitten effect, the Vanderbergh effect, Bruce effect

34. Effects of Pheromones AOB sends axons to medial nucleus of amygdala (MeA), projects to preoptic area, projects to anterior and ventromedial nucleus of hypothalamus VNO ▫Responds to non-volatile compounds found in urine or other substances ▫Essential for ability to rodent to identify sex of another rodent

35. Effects of Pheromones in humans Women who spent a large amount of time together tended to have synchronized cycles Women who spent time with men tended to have shorter cycles Men show a neural response to a chemical found in women’s urine ▫Estrogenic chemical estratetraene (EST) activated PVN and DMH in men but not in women Human VNO is non-functioning Pheromones appear to be detected by the “standard” olfactory system ▫EST activated the brains of men with intact olfactory systems, not in men with normal VNOs but not in olfactory epithelium was destroyed

36. Human Sexual Behavior Activational effects of sex hormones in women ▫In most female mammals (except higher primates), sexual behavior is controlled by ovarian hormones estradiol and progesterone  Control willingness and ability ▫In higher primates, ability to mate is not controlled by ovarian hormones  Ovarian hormones do influence a women’s sexual interest  Lesbian couples found a increase in sexual interest during middle portions of the women’s cycle  Women initiate sex more often around mid-cycle (ovulation, estradiol peaks) ▫May depend on circumstance

37. Human Sexual Behavior Activational effects of sex hormones in women ▫Women’s sexual interest can be stimulated by androgens  Ovaries (T) and adrenal glands (androstenedione)  Androgens by themselves (in the absence of estradiol) do not directly stimulate women’s sexual interest but appears to amplify the effects of estradiol ▫Ovariectomized women who were receiving E- replacement therapy were given T or placebo  T produced greater increase in sexual activity and rate of organism, higher levels of well-being

38. Human Sexual Behavior Activational Effects of Sex Hormones in Men ▫Men resemble other mammals in their behavioral response to T ▫Normal levels of T – potent, fertile ▫Without T – sperm production and sexual potency stop  Variable, perhaps depending on previous sexual history ▫T not only affects sexual activity but also is affected by it  Watching an erotic film increased T levels in men

39. Human Sexual Behavior Sexual Orientation ▫Best predictor of adult homosexuality was a self- report of homosexual feelings (preceded homosexual activity by ~ 3 years) ▫Not due to variations in hormone levels during adulthood ▫Hypothesis – subtle difference in brain structure caused by differences in the amount of prenatal exposure to androgens???

40. Human Sexual Behavior Sexual Orientation ▫Prenatal Androgenization of Genetic Females  Congenital adrenal hyperplasia (CAH)  Adrenal glands secrete abnormal amounts of androgens  Prenatal masculinization  Boys are normal  Girls have enlarged clitoris, partly fused labia  Once identified, person is given a synthetic hormone that suppresses the abnormal secretion of androgens  Increased homosexuality (1/3 are lesbians or bisexual)  Androgens affect development of brain

41. Human Sexual Behavior Sexual Orientation ▫Differences seen in sexual orientation are caused by effects of prenatal androgens on brain development?  Prenatal androgenization may be responsible for other sexually dimorphic behaviors  Girls with CAH produced drawings that were more “boy- like”, prefer “boy toys” Boys like active toys, girls like toys that provide opportunity for nurturing ▫Sex-typical play (environmental effect) ▫Babies (1 day old)  Boys prefer to watch a moving mobile, girls prefer to look at a female face

42. Human Sexual Behavior Sexual Orientation ▫Effects of rearing on sexual identity and orientation of prenatally androgenized genetic males  Bruce/Brenda/David  Cloacal exstrophy – birth of a boy with normal testes by lack of penis  Many boys raised as girls  50% of people were dissatisfied with their gender assignment and began living as men  Sexually orientated towards women ▫“Genetic males with male-typical prenatal androgen effects should be reared male”

43. Human Sexual Behavior Sexual Orientation and the Brain ▫Brain is sexually dimorphic  More cross talk between hemispheres in female brain  Less effect of stroke in females than males  Sizes of some specific regions of the telencephalon and diencephalon are different  May be due to androgens, environment, or combination of both ▫Brains of deceased heterosexual males, homosexual males, heterosexual females  Suprachiasmatic nucleus (SCN), sexually dimorphic region of the hypothalamus, anterior commissure  No relationship with sexual orientation

44. Human Sexual Behavior Sexual Orientation and the Brain ▫Bed nucleus of the stria terminalis (BNST) is larger in males than in females ▫Male-to-female transsexuals, BNST is the same size as in females ▫Female-to-male transsexuals, BNST is the same size as in males ▫Size of BNST was as large in male homosexuals as in male heterosexuals Size is related to sexual identity, not sexual orientation

45. Sexual Orientation and the Brain Uncinate nucleus of the hypothalamus (medial preoptic area in rats) ▫Twice as large in males than females ▫Size in male-to-female transsexuals is about the same as that of females Neurons in the uncinate nucleus send project to BNST Neural circuitry that affects a person’s sexual identity

46. Human Sexual Behavior Possible Causes of Differences in Brain Development ▫What causes high levels of prenatal androgens?  Increased number of older brothers  When mothers are exposed to several male fetuses, their immune system may become sensitized to proteins that only males possess  Response of mother’s immune system may affect prenatal brain development of later male fetuses  Only some mother’s become sensitive to a protein produced by their male fetuses

47. Human Sexual Behavior Heredity and Sexual Orientation ▫Males - Concordance rate was 52% for identical twins, 22 % for fraternal twins ▫Females - Concordance rate was 48% for identical twins, 16 % for fraternal twins ▫Increased incidence of homosexuality and bisexuality in sisters, daughters, nieces, and female cousins

48. Lecture Preview  Sexual Development  Hormonal Control of Sexual Behavior  Neural Control of Sexual Behavior  Parental Behavior

49. Neural Control of Sexual Behavior - Males Erection and ejaculation are controlled by circuits of neurons in spinal cord. Brain mechanisms control spinal cord circuits ▫Medial amygdala (MeA) – gets input from OB & AOB  Lesions of MeA abolish sex behavior in male rodents  Mediates effects of pheromones on male sex behavior ▫Medial preoptic area (MPA or MPOA)  Electrical stimulation elicits male copulatory behavior (Malsbury)  Sexual activity increases firing rate of neurons  Act of copulation increases metabolic activity and increases Fos protein  Mating increased release of glutamate, infusion of glutamate increased frequency of ejaculation  Destruction abolishes male sexual behavior

50. Neural Control of Sexual Behavior - Males Sexually Dimorphic structures: ▫Sexually dimorphic nucleus (SDN) – nucleus within MPA  3-7 times larger in males than females  Size of SDN is controlled by the amount of androgens present during fetal development  Critical period for masculinization of SDN appears to start on 18 th day of gestation and end once animal is 5 days old (rats are normally born on 22 nd day of gestation)  Lesions of SDN decrease masculine sexual behavior

51. Neural Control of Sexual Behavior - Males Sexually Dimorphic structures: MeA – one region in nucleus is 85% larger in males than females (lots of androgen receptors) Destruction disrupts sexual behavior Rats with lesions took longer to mount receptive females and ejaculate Mating increased production of Fos

52. Neural Control of Sexual Behavior - Males MPA ▫Receives input from MeA and BNST ▫Receives somatosensory information from the genitals through connections with central tegmental field (CTF) of the midbrain and MeA  Sex increases Fos in CTF and MeA  If rodent is castrated in adulthood, sex behavior stops, can be reinstated with T injections into MPA, MeA, or CTF ▫Receives input from periaqueductal gray (PAG) and nucleus paragigantocellularis (nPGi) of medulla  nPGi inhibits spinal cord sex reflexes (5-HT)  MPA suppresses inhibition by inhibiting PAG (excites nPGi)

53. Figure 10.19 Male Sexual Behavior

54. Neural Control of Sexual Behavior - Female Ventromedial nucleus of the hypothalamus (VMH) ▫Bilateral lesions will not display lordosis ▫Stimulation facilitates female sex behavior MeA projects to VMH ▫Copulation or mechanical stimulation of genitals of female rat increases Fos protein in MeA and VMH Sex behavior dependent on E & P ▫E primes, P stimulates sex behavior  Injections of E and P in VMH will stimulate sex behavior in rats without ovaries  Block of P receptors in VMH disrupts sex behaviors E and P exert their effects on sexual behavior through the VMH

55. Neural Control of Sexual Behavior - Female E increases production of P receptors, increases effectiveness of P VMH projects to PAG ▫Stimulation of PAG facilitates lordosis ▫Lesions of PAG disrupt lordosis ▫Lesions that disconnect the VMH from PAG abolish female sex behavior ▫E or electrical stimulation of VMH increased firing rate of neurons in PAG Pathway: VMH – PAG – nPGi – motor neurons in spinal cord

56. Figure 10.22 Female Sexual Behavior

57. Neural Control of Sexual Behavior Formation of Pair Bonds ▫5% of mammalian species, heterosexual couples form monogamous, long-lasting bonds  In humans, also seen in homosexual couples ▫In animals and humans, monogamy is not always exclusive ▫Relationship between monogamy and 2 peptides in the brain  Vasopressin and oxytocin  Released from posterior pituitary gland, NTs in brain  In males, vasopressin plays a bigger role in pair bonding ▫Monogamous voles have a higher level of V1a vasopressin receptors than polygamous voles ▫Injected virus that overexpressed V1a receptors into ventral forebrain of polygamous voles ▫Increased V1a receptors, voles became monogamous

58. Neural Control of Sexual Behavior Formation of Pair Bonds ▫In female voles, oxytocin plays a bigger role in pair bonding  Mating stimulations release of oxytocin  Peripheral injection or ICV injection of oxytocin facilitates pair bonding in female voles  Blocking oxytocin receptors disrupts formation of pair bonds ▫May be consistent in humans?  Oxytocin increases trust, relaxation, calmness, well- being

59. Lecture Preview  Sexual Development  Hormonal Control of Sexual Behavior  Neural Control of Sexual Behavior  Parental Behavior

60. Parental Behavior Maternal Behavior of Rodents ▫During gestation female rats build nests  Brood nest ▫Child birth (parturition) and prenatal hormones that induce a female rat to begin taking care of pups Hormonal Control of Maternal Behavior ▫No evidence that organizational effects of hormones play a role in maternal behavior  Even males will take care of babies ▫Maternal behavior is affected by hormones, it is not controlled by them  Virgin female rats will begin to retrieve and care of babies after having babies placed with them for several days  Once the rat is sensitized, they will take care of pups as soon as they encounter them - forever

61. Parental Behavior Hormonal Control of Maternal Behavior ▫Nest-building behavior is facilitated by progesterone  After parturition, moms continue to maintain a nest, or build a new one, even though P levels are low ▫Hormones that influence a female rat’s responsiveness to her babies  Estradiol, progesterone, prolactin  Prolactin – hormone of anterior pituitary bland, necessary for milk production ▫In some species, oxytocin is involved in formation of bond between mom and baby  In rats, administration of oxytocin facilitates the estabilishment of maternal behavior  Injection of oxytocin antagonists at birth caused female rats to ignore babies

62. Parental Behavior Neural Control of Maternal Behavior ▫MPA  Lesions disrupt both nest building and pup care  Moms ignored babies  Metabolic activity increased immediately after parturition  Virgin females whose maternal behavior had been sensitized by exposure to pups showed increased activity in MPA  Prolactin exerts its stimulating effect on maternal behavior by acting on receptors in MPA  Infusion of prolactin antagonist into MPA delayed onset of maternal behavior

63. Parental Behavior Neural Control of Maternal Behavior ▫Olfaction plays a key role in sensitization of maternal behavior in rats  Virgin female rats will avoid pups as if she was repelled by the pup’s odor  Without olfaction, female rats started taking care of the pups sooner ▫Also necessary to initiate processes that make pups and their odors attractive ▫Appear to be mediated by the MPA  Inhibition of circuits responsible for the aversion to odor of pups  Activation of circuits responsible for caring for pups

64. Parental Behavior Neural Control of Maternal Behavior ▫Aversive response that virgin females make toward odor of pups  Olfactory system inputs to MeA  Lesions of MeA abolish the aversion of virgin females to pups  MeA projects to anterior hypothalamus (AH), projects to PAG (avoidance responses)  MPA inhibits activity of AH-PAG circuit Figure 10.26 Habituation to the Aversive Effect of the Odor of Pups

65. Parental Behavior Neural Control of Maternal Behavior ▫Neural circuitry responsible for caring for pups  MPA projects to VTA and retrorubral field of midbrain  Dopaminergic neurons in VTA project to NAC (involved in motivation and reinforcement) ▫Lesions of NAC disrupts maternal behavior  NAC projects to ventral pallidum (part of basal ganglia) involved in control of motivated behaviors

66. Parental Behavior Neural Control of Parental Behavior ▫Size of MPA, essential role in maternal behavior, shows less sexual dimorphism in monogamous voles than in promiscuous voles  Increased fos expression in MPA when monogamous voles were exposed to a pup  Lesions of MPA produce severe deficits in paternal behavior of male rats