Reproductive Behavior Flashcards
compare and contrast asexual and sexual reproduction.
Asexual reproduction in some animals (parthenogenisis)
All eggs genetically identical to mother
Came from sexual reproduction but these animals lost the ability to sexually reproduce
Vast majority of vertebrates sexually reproduce
Sexual reproduction produces more genetic variation
In hopes that one will survive better
why are female gametes larger than male gamete?
Females gametes/ eggs carry the organelles for the reproduction, so larger gamete, limited by number gametes
Sperm generally carries DNA, have flagellum
Male gametes are smaller and designed for motility to find the eggs, smaller than female gametes, limited in number of mates.
precursors to female and male internal structures?
Mullerian ducts are precursors to female internal structures
Wolffian ducts are precursors to male internal structures
what causes differentiation into male genitals?
Gene on the male’s Y chromosome the SRY gene (sex determining region on the Y chromosome causes those differentiating gonads to develop into testes, the sperm producing organs
Testes produce androgens (hormones more abundant in males) and increases the growth of testes which would then produce more androgens
Androgens cause wolffian ducts to develop into seminal vesicles (stores semen) and the vas deferens (ducts from testes to penis)
Testes produce mullerian inhibiting hormone (MIF) that causes mullerian ducts to degenerate
Male testes produce more androgens than estrogens (hormone abundant in females)
what causes differentiation in external genitals?
In mammals differentiation of external genitals depends mainly on T
High levels of T causes external genitals to develop male pattern and low levels leads to a female pattern
First trimester is the human sensitive period for genital formation
Male developing testes secrete testosterone , certain enzymes convert it into dihydrotestosterone - very effective at promoting penis growth: if dihydrotestosterone levels is high enough the tiny genital tubercle grows and develops into a penis but if levels are low, the tubercle develops into a clitoris
Depending on levels of T and dihydrotestosterone , the embryo develops either a scrotum or labia
what causes differentiation into female genitals?
do not have the SRY gene, their gonads develop into ovaries and their wolffian ducts degenerate
Ovaries do not produce MIH- females’ mullerian ducts develop and mature into oviducts, uterus, and upper vagina
Female ovaries produce more estrogens than androgens
prominent androgens and estrogens
Prominent androgen =testosterone
Prominent estrogen = estradiol
have similar effects in some ways and opposing effects in others
progesterone
Progesterone- another prominent female hormone- prepares uterus for implantation of a fertilized ovum and promotes the maintenance of pregnancy
Progesterone released by the corpus luteum in the ovary peaks a bit later -different from rodents; to create a good place for the egg to develop- progesterone stimulates uterine development
genes and sex differences
Y and x chromosomes control some biological differences independently of hormones
Y chromosome has many sites that alter the expression of genes on other chromosomes
Genes on X and Y chromosomes produce effects beyond those that we can trace to androgens and estrogens
sexual selection
genes that make an individual more appealing to the other sex will increase the probability of reproduction
Male sexual behavior- dopamine mesocorticolimbic system
Appetitive (motivation)- sex drive, libido courtship
E.g. vocalizations, movement in search of mates
Consummatory- copulatory behavior
Sexual attraction is largely driven olfactory & auditory
Mounting (latency)
Intermount (interval)
Intromission (insertion of penis) number
Ejaculation (number)
Ultrasonic vocalizations esp after copulation and self grooming
Sensitive to Environmental context & testing paradigm
testosterones effects on male sexual behavior
T is essential for male sexual arousal, and acts partly by increasing the sensitivity in the penis
Sex hormone bind to receptors that increase responses in parts of the hypothalamus, including the ventromedial nucleus, the medial preoptic area (MPOA) and the anterior hypothalamus
T primes the MPOA and several other brain regions to release dopamine
MPOA neurons release dopamine strongly during sexual arousal
Both men and women with high T levels are more likely than average to seek additional partners
Decreases in T levels generally decrease male sexual activity
Androgen do not “cause male sexual behavior, but rather androgens change the probability that male sexual behavior will be elicited within a particular context- like a dimmer not a switch
dopamine effects on male sexual behavior
in moderate concentrations, dopamine stimulates mostly type D1 and D5 receptors which facilitate erection of the penis in the male and sexually receptive postures in the female
in higher concentrations of dopamine, dopamine stimulates type D2 receptors which lead to orgasm
dopamine stimulates sexual activity, the neurotransmitter serotonin inhibits it by blocking dopamine release.
many antidepressant drugs increase serotonin activity, and one of their side effects is decreased sexual arousal
inability to have an erection is likely due to
Low T is not usual basis for impotence, the inability to have an erection (usually caused by impaired blood circulation, especially in older men
how does viagra work
The drug sildenafil (Viagra) increases male sexual ability by prolonging the effects of nitric oxide which increases blood flow to the penis and blood flow to the brain
activational effects
Activational effects- after reproductive maturity, transient modification behavior, usually after puberty (day 40-50 in rats)- can be both genomic and non-genomic
Genomic effects are mediated by effects in transcription and tend to be longer lasting
Non-genomic effects are quite rapid and do not involve transcription and translation and can involve second messengers
Temporary effects continuing only while a hormone is present or shortly beyond
Current hormones influence the degree of sex drive
Bursts of hormone during pregnancy produces temporary effects on emotional arousal , aggressive behavior and learning and cognition
Organizing effects set the stage for activating effects
organizational effects
Organizational effects - early development, long lasting structural effects and often epigenetic in nature, small increase in testosterone after birth to masculinization the brain
Hormones injected early in life have much stronger effects
Sensitive period in early development (e.g. first trimester of pregnancy for humans, sex hormones determine whethter the body develops into female or male genitals and alters certain aspect of brain development)
Organizational effects during puberty: breast development on women, facial hair and penis growth in males, changes in voice, and male-female differences in the anatomy of certain parts of the hypothalamus; some of the differences in brain anatomy between males and females increases during this time
Organizing effects set up the female hypothalamus such that later hormones can activate the menstrual cycle
distinction between organizational and activational effects
Distinction between organizing and activating effects is not absolute, hormones often produce a combination of temporary and longer-lasting effects
how can we test the effects of T and other hormones
Remove testes, give back testosterone
Slow release implants: Silastic capsule-silicon implants- made of silicon, tubing filled with crystalline testosterone and sealed; the longer the tube, the more testosterone- way of administering testosterone without injection and lasts for weeks in the system for longer and less stressful effects.
ICB administration- brain or part of exposed to androgen, received in the ventricle
Testosterone
Testosterone crosses BBB quite easily and effects all around body as it is a small lipophilic molecule
aromatase
Aromatization in specific brain regions is crucial Important for male sexual behavior which is counter-intuitive since it creates estrogens Converts androgen (testosterone) into estrogen (estradiol) the estradiol then binds to estrogen receptors which has effects on gene expression (genomic effects)
in castrated male rats, what did T and E2 administration, and aromatase inhibitor (block activity of enzyme) show?
systemic T, androstenedione-weak androgen precursor to testosterone (also restoration to male sexual behavior), and E2 (estradiol) restore appetitive and consummatory behaviors
T+ aromatase inhibitor (block activity of enzyme)
Reduction in male sexual behavior
how do you increase amount of aromatase, inhibit aromatase in the brain, and locate it?
Increase amount of aromatase with viral vector to over express aromatase
inhibit neurons containing aromatase with optogenetics
Located aromatase in brain- in situ hybridization- mRNA
Look for aromatase protein using immunohistochemistry
Take tissue and homogenize i test tube and add radiolabeled testosterone and see active aromatase that produces radiolabeled estradiol
how are rats masculinized?
In male rats, testosterone begins masculinizing the external genitals during the last several days of pregnancy and first few days after birth and continues masculinizing at declining rate for the next month
female rats injected with T
Female rat is injected with testosterone during last few days of pregnancy or after birth is partly masculinized, just as if her own body had produced the T: exhibiting larger cliterous and shows male sexual behavior and thus, early T promotes male patterns and inhibits female patterns
male rats given estrogen
Injecting male with estrogens produces little effects on his external anatomy but if he lacks androgen receptors, he develops female typical pattern of anatomy and behavior
cause of low androgen receptors
could be an outcome of castration, genetic deficiency of an androgen receptors, or prenatal exposure to drugs that interfere with androgen response (e.g. alcohol, weed, haloperidol- antipsychotic drug, phthalates- common in manufactured products and cocaine)- amount of interference depends on type of drug and amount of exposure, even aspirin interferes with male pattern of development
effects of phthalates
Phthalates inhibit T production: sons of women with high phthalate levels showed less interest in typical boys toys and more interest in typical girls toys and suggests that prenatal hormones especially T alter the brain in many ways that influence differences between boys and girls activities and interest
prostate glands
gland that produces a fluid accompanies and protects sperm cells when ejaculated during intercourse
females lacking estradiol
Female that lack estradiol during early life develops rather normal female external anatomy but does not develop normal sexual behavior or normal internal anatomy; even if she is given estradiol injections , she will show little sexual response to anyone; estradiol is essential for female development
sexual differentiation in the brain for rats in terms of estrodiol and T
Rats Early development (shortly before or after birth) the blood contains high levels of alpha-fetoprotein that binds to circulating estradiol and prevents from entering cells; Female brain is not exposed to estradiol at this time
male T is free to enter the hypothalamus where the enzyme converts much of it to estradiol, and exerts masculinizing effects at this time
For early developing rodents, T is a way of getting estradiol to the hypothalamus
prolactin
Mammalian mother delivers her babies, she increases her secretion of oxytocin and prolactin which promote milk production and several aspects of maternal behavior
Prolactin inhibits sensitivity to leptin, promoting feeding
Man’s testosterone level declines and his prolactin level increases when a baby is born but only if the man has a close relationship with the mother and only in societies where men contribute to infant care
Men with lower T levels and higher prolactin levels spend more time playing with and caring for their children but these are correlational data
vassopressin
Vasopressin synthesized by the hypothalamus and secreted by the posterior pituitary gland
Vasopressin is important for social behavior in many species partly by facilitating olfactory recognition of other individuals
Males with highest vasopressin levels show highest levels of sexual fidelity to their mates
Low vasopressin levels, mate and then ignore the female and her young
Men with genes for less active forms of vasopressin receptor are less likely to marry, more likely to have marital conflicts or threat of divorce- less likely to show altruistic behavior
Women with the less active form of the receptor were less attentive to their young children
Female rats ignore or avoid baby rats mainly because of aversion of the odor
animals with plenty of T, if aromatase is inhibited
there is a gradual decrease in appetitive sexual behavior
Non-genomic (rapid) effects of estrogens on male appetitive sexual behavior
Single s.c. injection of vehicle control ( C) or vorozole (VOR) an aromatase inhibitor
Half of VOR- treated subjects received E2 concurrently
After 30 min (shorter than previous test), measured time at window
Vorozole rapidly decreases time at window
With estradiol- more time at window, if anything higher than control, possibly because estradiol dose was higher
Suggesting estradiol as non-genomic effects
Other ways to test non-genomic effects
Give estradiol that is conjugated (connected) to a large protein and thus cannot cross cell and cannot bind to the receptors of the nucleus but could bind to receptor at the plasma membrane- and thus still have a rapid effect
Other studies have given an inhibitor of transcription (low dose for short amount of time to not kill the cell) and shown that estrogens can have an effect on behavior or some effect on brain even with the presence of inhibitor
autoradiography
using radiolabeled hormones (testosterone or estradiol), and injecting into animals that has been gonadectomized (removing endogenous hormones) doesn’t compete with regular production of testosterone.
The tissue is then sectioned and applied to autoradiographic film and develop the film to expose where there is radioactivity.
Not as sensitive as immunohistochemistry
In Situ Hybridization or PCR to look for mRNA for the receptors
Social behavior network
Pattern of activation is important for various behaviors
Important for all kinds of behavior regulated by network
Interconnected parts of the brain
Cfos protein is expressed after some stimulus, indirect way of looking at neuronal activation
Male rat had sex and they looked for cfos in the brain 90 mins later- animal killed
There was a lot of activation in the medial amygdala and preoptic area
Less activation in the anterior hypothalamus which is more activated by aggressive behavior
This is a way of mapping out neuronal activation, following different social behavior
Circuit for male sexual behavior
mPOA- medial preoptic area, and medial amygdala that have a lot of aromatase and are part of the social behavior network- important for male reproductive behavior
Ventral tegmental area and the midbrain and spinal cord
Neurons in the spinal cord are important for erecting the penis and ejaculation, not so much in humans but there are androgens in the motor neurons
Testosterone facilitates the release of dopamine in the mPOA and other areas which stimulates behavior
hypogonadal men
men with low levels of testosterone- could be a problem in the hypothalamus, pituitary, testes
how can T be measured in the plasma
immunoassay
DHT
DHT can also reinstate sexual behaviors in hypogonadal men
DHT does not get converted into estrogen
DHT is longer lasting version of T
DHT has little effect on sexual behavior in castrated rodents
But has effect in humans
effects of E2 on hypogonadal men
E2 is not effective in hypogonadal men in contrast to castrated rodents and quail where there is an effect
Clear species differences
estrous cycle
component of female rodent sexual behavior
Estrous cycle- 4 days long- dark bar (lights off)
Ovulate at night (progesterone levels peak just before ovulation)
During behavioral estrus (showing receptive behavior also when estrogen levels peak) , highest levels of:
Attractivity: to test, 2 females are tied on opposite chambers and male can go back and forth between chambers. Assess time male spends in each chamber or in the middle. Males are more attracted to females in behavioral estrus driven largely by olfaction
proceptivity
Female initiation of copulation
Sexual Motivation
E.g., in female rats, willingness to cross electrified grid to mate with male, lever pressing for access to male
In rats, hopping and darting, ear wiggling
Female rhesus monkeys will press a lever (e.g. a ratio of 250 times) in order to gain access to a male monkey
Operant conditioning
Faster lever pressed, more motivation
Time taken to complete lever pressing was shorter
how to test proceptivity
Progressive Ratio Test: increases lever presses for door to open; at what point do they stop pressing the button, higher the break point, the more motivated for quantification
receptivity
Responsiveness to male initiation
E.g. lordosis/consummatory behavior
lordosis - 4 point scale
LQ= lordosis quotient (0 to 100%) - number of times female lordosis divided by number of times male mounts
Lordosis is estrogen sensitive
Ovariectomy (OVX) greatly reduces receptivity in rats
In some primates, OVX females remain receptive (decreases by not that much)
Estradiol promote lordosis behavior
Social behavior network after sex for female rats after lordosis
Pattern of of activity
Ventromedial hypothalamus
Midbrain ventrotecmental area with lots of dopaminergic neurons
ERs in female animal brain
Autoradiography: E2 concentration cells in hypothalamic, limbic, and mesencephalic structures
Animals are ovariectomized and injected with radiolabeled estradiol
ERs in vlVMH (ventral lateral VMH) are critical for female sexual behavior
vlVMH lesion? infuse estrogen receptor agonist? In ovariectomized animals, if infused estradiol specifically to vlVMH?
Lesion vlVMH- reduction in lordosis
Infuse estrogen receptor antagonist- prominent reduction in lordosis
In ovariectomized animals, if infused estradiol specifically to vlVMH- increases in lordosis
Endocrine Regulation of Receptivity in female rodents
E2 + PROG sequentially is more effective in inducing lordossis than E2 alone; although estradiol works slowly
In OVX rats sexual behavior can be restored by E2 followed by PROG treatment
Mimics the estrous cycle
Strong female sexual behavior
In rats, PROG treatment is 2 days after E2
Testing is 4 hours after PROG
brain responsiveness/sensitivity to progesterone
Progesterone receptors fluctuate throughout the cycle: appear then disappear
Use track tracer; anterograde, to see connections between brain regions
Lots of progesterone receptors in the VMH
Estrogen affects neurons at the VMH and in the periaqueductal grey
how does lordosis in rats occur?
Estrogen affects neurons at the VMH and in the periaqueductal grey
VMH Regions then project these neurons in periaqueductal grey to the medulla then the spinal cord(important for lordosis posture)
anterograde and retrograde tracers
Inject anterograde tracers in the VMH to see which regions it projects to; retrograde tracers in the periaqueductal grey, then we see cell bodies labelled in the VMH which confirms the connection
menstrual cycle
hypothalamus and pituitary interact with the ovaries to produce the menstrual cycle, a periodic variation in hormones and fertility over the course of about 28 days
After end of menstrual period, the anterior pituitary releases follicle-stimulating hormone (FSH) which promotes the growth of a follicle in the ovary
Follicle nurtures the ovum (egg cell) and produces several types of estrogen including estradiol
Towards middle of menstrual cycle, the follicle builds up more and more receptors to FSH so even though he actual concentration of FSH is decreasing , its effect on follicle increase
The follicle produces increasing amounts of estradiol; increased release of estradiol causes increased release of FSH and a sudden surge of luteinizing hormone (LH) from the anterior pituitary
FSH and LH combine to cause the follicle to release an ovum
Remnant of the follicle release the hormone progesterone which prepares the uterus for implantation of a fertilized ovum
Progesterone also inhibits further release of LH
If pregnant, estradiol and progesterone levels continue to increase and if not pregnant, both hormones decline , the lining of the uterus is cast off (menstruation) and cycle begins again
LH and FSH are hormones released by the anterior pituitary and peak right before ovulation to stimulate ovulation
Estradiol also peaks at around ovulation
Periovulatory period
time when ovulation occurs; when egg is released into the fallopian tubes
Women’s estradiol levels peak sharply during the periovulatory period, days around the middle of the menstrual cycle when fertility is the highest
Women not taking birth control pills initiate sexual activity more often during the periovulatory period than at other times of the month
Unmarried women flirt with an appealing man more during this period than other times
Women during the periovulatory period become more likely than usual to wear red or pink, colors that most men consider sexy
sexual desire in women
Administering enough estradiol to return it to normal levels increases sexual desire
Increasing testosterone can increase a women’s sexual desire but only if administered levels far beyond what a women would produce naturally
Sexual desire correlated strongly with changes in levels of estradiol not T
In female rats, a combination of estradiol and progesterone is the most effective combination for enhancing sexual behavior
Estradiol increases the sensitivity of the pudendal nerve which transmits tactile stimulation front he vagina and the cervix to the brain
Birth control pills
Birth control pills prevent pregnancy by interfering with the usual feedback cycle between the ovaries and pituitary
Not always negative feedback, some cases positive feedback; the estradiol coming from the ovary stimulates the release of gonadotropins from the pituitary which then stimulates estradiol production- birth control pills prevent this
Birth control pills can cross the blood brain barrier as these steroid hormones are lipophilic and binds to receptors wherever in the brain
Alters ovulation and behavior
combination pill
The combination-pill contains an estrogen and progestin
Prevents the surge of FSH and LH (gonadotropins) that would release an ovum
The estrogen-progesterone combination thickens the mucus of the cervix, making it harder for sperm to reach the egg, and prevents and ovum, if released from implanting in the uterus
human attracitvity
Men prefer scent of ovulating women
Some evidence that humans can detect these hormonal scents
Got men to smell armpit of t-shirt of women at different points in cycle; asked to rate the smell
Human Proceptivity
Testosterone levels in the blood are associated with proceptivity
Cyclicity of behavior is gone with birth control pills
There is a peak in initiation during ovulation
Sexual interest peaks at the periovulatory period and influences behavior in many ways generally without the women’s conscious recognition of the effect
Human receptivity
Studies suggest women are more sexually receptive during the periovulatory period (around the time estimating ovulation)- similar to rodent work, less likely to get pregnant
difference between sex and gender differences
Differences that result from biological differences are generally referred to as sex differences
Differences that result from people’s thoughts about themselves as male or female are generally referred to as gender differences
hermaphrodites
Hermaphrodite has anatomy intermediate between male and female or show a mixture of male and female anatomies
A true hermaphrodite has some testicular tissue and some ovarian tissue
One way for this to happen is for a woman to release 2 ova each fertilized by a different sperm then fuse instead of becoming twins; if one had a XX chromosome and the other had a XY, the resulting child would have some XX cells and some XY cells
True hermaphrodites are rare and some are fertile as either male or female but none are fertile as both
intermediate appearance commonly due to
atypical hormone pattern
A genetic male with low levels of T or a deficiency of T receptors may develop a female or intermediate appearance
A genetic female who is exposed to more T than the average female can be partly masculinized
congenital adrenal hyperplasia (CAH)
overdevelopment of of the adrenal gland from birth
Ordinarily the adrenal gland has a negative feedback relationship with the pituitary gland as the pituitary secretes adrenocorticotropic hormone (ACTH) which stimulates the adrenal gland
Cortisol, one of hormones from the adrenal gland, feeds back to decrease the release of ACTH. some people have a genetic limitation in their ability to produce cortisol; if the pituitary fails to receive much cortisol as a feedback signal, it continues secreting more ACTH causing the adrenal gland to secrete more and more of its other hormones including testosterone
In genetic male, the extra T causes little effect
Genetic females with this condition develop various degrees of masculinization of their external genitals (the ovaries and other internal organs are less affected)
intersex
A person whose sexual development is intermediate
Some are given surgery to alter their external genital appearance
An estimated 1 in 100 children in US is born with some degree of gential ambiguity and 1 in 2000 has enough ambiguity to make its male or female status uncertain
traits of girls with CAH
Girls with CAH played with boys toys more than most other girls did but less than the average for boys; when the children tested with parents, the CAH girls were intermediate between the other 2 groups
Girls with CAH perform slightly better than most other girls do on spatial and mechanical skills, on which boys generally do better than girls
A study of girls with CAH in adolescence found that on average their interests are intermediate between those of typical male and female adolescents
Girls with CAH have a difficult sexual adjustment, especially if they were subjected to clitoris reduction surgery
Testicular feminization
certain individuals with an XY chromosome pattern produce normal amounts of androgens including testosterone but the lack the receptor that enables those chemicals to activate genes in a cell’s nucleus
Cells do not respond to androgens
Smaller size penis to genitals like those of a typical female in which no one has any reason to suspect the person is anything other than female until puberty
breasts develop and hips broaden but she does not menstruate because her body has internal testes instead of ovaries and a uterus; the vagina is short and leads to nothing but skin; pubic hair is sparse or absent because it depends on depends on androgens in females and males
Psychologically she develops as a typical female
Cloacal exstrophy
genetic males are born with a very small penis which is a defect of the pelvis development; despite their small penis, they have typical male levels of T in prenatal development
Males with cloacal exstrophy who are reared as girls all develop typical male interests, many or most demand assignment as males and nearly all develop sexual interest towards women
dihydrotestosterone
Dihydrotestosterone is more effective than T for masculinizing the external genitals
Certain genetic males fail to produce 5-alpha- reductase 2
an enzyme that converts T to dihydrotestosterone
These individuals appear to be female though have some swollen clitoris and somewhat lumpy labia
They are considered girls and reared as a girl but their brains have been exposed to male levels of T during early development
At puberty the T levels increase sharply and even without the conversion to dihydrotestosterone, the result is the growth of a penis and scrotum enough to be clearly male
Sex differences in human Brain
Differences in the hypothalamus, cortical area, pituitary glands, parts of the spinal cord and elsewhere
Female hypothalamus generate a cyclic pattern of hormone release whereas males release hormones more readily
SCN bigger in women
Estradiol acts by different routes in different parts of the hypothalamus
VMH
In part of the ventromedial hypothalamus, estradiol activates an enzyme called PI3 kinase that increases the release of glutamate from presynaptic neurons, and causes postsynaptic neurons to increase their dendritic branching
The ventromedial hypothalamus contributes to aggressive and sexual behavior and feeding
In Arcuate nucleus and the anteroventral periventricular nucleus, estradiol increases ____ production, which acts on the astrocytes to decrease dendritic spines which results in shrinkage of these areas for males; remain large for females because low levels of___ in early in life
GABA, estradiol
T acts on_____directly instead of by conversion to estradiol
hypothalamus
Sex differences in play
Children who show the greatest pattern for boy typical activities at age 3 usually show the greatest amount of boy typical activities at age 13; same with females c
Girls who had been exposed to higher levels of T in prenatal life showed slightly higher preference for boys toys
Sexual Orientation in gay men
Most men discover their sexual orientation earlier in developments
They do not “choose”
Generally occurs later in women
Biological predisposition might be stronger for men than women
homosexual genetics
No single gene has been identified
Some studies reported that homosexual men had higher incidence of homosexual men had higher incidence of homosexual relatives (uncles) on maternal side than paternal side
Implications; X chromosome gene involved but no replications
But other studies have not confirmed this pattern
homosexual Early Hormonal influences
Sexual orientation is not correlated with adult hormone levels (testosterone, estradiol, etc)
Adult homosexual men and women have hormone levels are similar to those of adult heterosexual men and women
Youngs experiment on sexual behavior (mounting) with hormones
Hypothesis: hormones in early development important for reproductive behavior in adulthood
Adult males respond to T manipulations
Adult females do not respond to T manipulations and or overactomy- no mounting
Lordosis
Prenatal T treatment reduced lordosis in response to estradiol and progesterone in adulthood
Prenatal T treatment increased mounting; strong role of hormones in development
Natural increase in T in males in early development
Early hormones in conjunctions with hormones in adulthood is very important for sexual behavior
Prenatal stress- rats
Random assignment of pregnant mothers
Last week of pregnancy only
Control or stress (2 hours of restraint per day in tube)
No pain just psychologically painful
Examined sexual behavior of offspring as adults
Daughters: no group differences in sexual behavior
Sons: mounting in response to male and lordosis with female
Stress could affect HPA axis and effect testosterone levels
Early life influences seemed to be more affected for sons for later behavior
Most males that were subjected to either prenatal stress or alcohol developed male sexual behavior in addition to these female sexual behaviors, but those that were subject to both alcohol and stress had decreased male sexual behaviors
what happens to Mother’s immune system when pregnant
Mother’s immune system suppressed when pregnant so moms immune system does not attack the fetus
why do Homosexual men have more older biological brothers regardless of number of other siblings
Key is how many previous times the mother gave birth to a son as the mothers’ immune system sometimes reacts against the protein in a son and then attacks the subsequent son enough to alter their development
Later born homosexual men tend to be shorter on average
Mother’s immune system might respond more strongly to a protein in the male fetus from Y chromosome
Mom’s immune response may respond greater to males than female fetuses
Has not been replicated
prenatal stress on brain
Prenatal stress and alcohol may alter brain development through several routes
Stress releases endorphins which antagonize the effects of T on the hypothalamus
Stress also elevates levels of certain adrenal hormones (corticosterone in rats, cortisol in human) that decrease testosterone release
Long term effects of either prenatal stress or alcohol include several changes in the structure of the nervous system, making the affected males anatomy closer to that of females
Genetic or epigenetic factors contribute as well as prenatal environment and alter experiences
sexual orientation and Brain Anatomy
the right hemisphere is a few percent larger in heterosexual males
Heterosexual women and homosexual men have more widespread connections in the left amygdala compared to the right amygdala
Heterosexual males, the right amygdala has more widespread connections
connections and the size of hemispheres
The anterior commissure is larger in heterosexual women than in heterosexual males, while in homosexual males the anterior commissure is at least as large as the heterosexual womens perhaps even slightly larger
Smaller third interstitial nucleus of the anterior hypothalamus (INAH 3- a subdivision of a subdivision of the preoptic hypothalamus): generally more than twice as large in heterosexual men as in women. This area has more cells with androgen receptors in men
__________ can change brain anatomy
Persistent behaviors
INAH 3
(small area) is in human within POA - preoptic area, area thought to be involved in sexual behavior, part of social behavior network important in social behavior including sexual behavior
Found that mean volume of INAH-3 was larger in heterosexual men than in heterosexual women or gay men who were about equal
But there were a substantial amount of variation among individuals
Nissl stain- post mortem tissue
This study is correlational study
critisms of LeVays INAH3 study
These structures are difficult to see in Nissl-stained sections- borders are not distinct
All the gay men have AIDS which is a limitation as the difference may arise from AIDS rather than sexuality
He measured region volume only, not cell number or gene expression etc.
Inadequate sexual histories of subjects- made presumptions about sexuality of people
mating systems define: polygyny polyandry social monogamy genetic monogamy
Polygny (male mates with multiple females)
Polyandry (female mates with multiple males)- rarer, some bird species
Monogamy (male-female pair)
Social monogamy- live in pairs, although they might mate outside of the pair; many birds
Genetic monogamy- mate strictly within the pair; some birds and fish
Tested by observations, genetic testing of offsprings
Prairie Voles
Long term pair bond; show monogamy
Vasopressin- hormone released by the posterior pituitary; small (9amino amino acids)
non-monogamous
Males: higher expression in lateral septum (LS) - part of social behavior network
Monogamous males: higher expression in ventral pallidum (VP)- different brain area that is ventral to the lateral septum
In females; the oxytocin receptors are different rather than the vasopressin receptors
Correlation between pattern of receptor of AVP and sexual behavior
Increase V1aR in VP (ventral pallidum) of adult non-monogamous males meadow voles
used viral vector to upregulate the amount of V1a : Shifts behavior- partner preference, does not make them monogamous in 3 chamber test
Does not become monogamous
But remembers the female mated with and prefers the previously mated female
oxytocin
Pituitary hormone oxytocin is important for reproductive behavior: oxytocin stimulates contractions of the uterus during delivery of a baby and it stimulates the mammary gland to produce milk; promote maternal behavior, social approach, and pair bonding
Sexual pleasure also releases oxytocin especially at orgasm
a state of relaxation shortly after orgasm as a result of oxytocin release
Viewing photos of your beloved activates the _____ and other areas important for memory and cognition
What we call love combines motivation, emotions, memories, and cognition
hippocampus
oxytocin administration
Oxytocin passes directly from the nasal cavity to the brain and exerts effects about half an hour later
oxytocin did not increase attraction to everyone, but just to someone already loved
Oxytocin enhanced man’s fidelity to his partner, decreasing his willingness to face the temptation of another attractive woman
Oxytocin helps people who have trouble recognizing faces and people who can recognize faces but have trouble identifying their emotional expressions
Oxytocin increases trust towards your in group members but could not increase, decrease, or have no effect on trust toward other people, depending on what you think of those people
increases attention to important social cues
